U.S. patent application number 16/515145 was filed with the patent office on 2021-01-21 for functional chromium alloy plating from trivalent chromium electrolytes.
The applicant listed for this patent is THE BOEING COMPANY. Invention is credited to Stephen P. GAYDOS, Vijaykumar IJERI, Subramanian MOHAN.
Application Number | 20210017659 16/515145 |
Document ID | / |
Family ID | 1000005005284 |
Filed Date | 2021-01-21 |
United States Patent
Application |
20210017659 |
Kind Code |
A1 |
IJERI; Vijaykumar ; et
al. |
January 21, 2021 |
FUNCTIONAL CHROMIUM ALLOY PLATING FROM TRIVALENT CHROMIUM
ELECTROLYTES
Abstract
The present disclosure provides electrolyte solutions for
electrodeposition of chromium-iron alloys and methods of
electrodepositing chromium-iron alloys. An electrolyte solution for
electroplating can include a trivalent chromium salt, an oxalate
compound, an iron salt, an aluminum sulfate, an alkali metal
sulfate, and an alkali metal halide. An electrolyte solution can be
formed by dissolving a trivalent chromium salt, an oxalate
compound, an iron salt, an aluminum sulfate, an alkali metal
sulfate, and an alkali metal halide in water or an aqueous
solution. Electrodepositing chromium-iron alloys on a substrate can
include introducing a cathode and an anode into an electrolyte
solution comprising a trivalent chromium salt, an oxalate compound,
an iron salt, an aluminum sulfate, an alkali metal sulfate, and an
alkali metal halide. Electrodepositing can further include passing
a current between the cathode and the anode through the electrolyte
solution to deposit chromium and iron onto the cathode.
Inventors: |
IJERI; Vijaykumar; (Mumbai,
IN) ; GAYDOS; Stephen P.; (St. Louis, MO) ;
MOHAN; Subramanian; (Chennai, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE BOEING COMPANY |
Chicago |
IL |
US |
|
|
Family ID: |
1000005005284 |
Appl. No.: |
16/515145 |
Filed: |
July 18, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 3/06 20130101; C25D
17/10 20130101 |
International
Class: |
C25D 3/06 20060101
C25D003/06; C25D 17/10 20060101 C25D017/10 |
Claims
1. An electrolyte solution for electroplating comprising: a
trivalent chromium salt; an oxalate compound; an iron salt; an
aluminum sulfate; an alkali metal sulfate; and an alkali metal
halide.
2. The electrolyte solution of claim 1, wherein: the trivalent
chromium salt is present in an amount ranging from about 0.3 moles
per liter to about 0.9 moles per liter of the electrolyte solution;
the oxalate compound is present in an amount ranging from about 0.2
moles per liter to about 1.2 moles per liter of the electrolyte
solution; the iron salt is present in an amount ranging from about
0.005 moles per liter to about 0.2 moles per liter of the
electrolyte solution; the aluminum sulfate is present in an amount
ranging from about 0.05 moles per liter to about 0.5 moles per
liter; the alkali metal sulfate is present in an amount ranging
from about 0.1 moles per liter to about 2.0 moles per liter of the
electrolyte solution; and the alkali metal halide is present in an
amount ranging from about 0.1 moles per liter to about 0.5 moles
per liter of the electrolyte solution.
3. The electrolyte solution of claim 1, wherein the iron salt is a
divalent iron salt comprising one or more of iron (II) sulfate,
iron (II) chloride, iron (II) acetate, and hydrates thereof.
4. The electrolyte solution of claim 1, wherein the iron salt is a
trivalent iron salt comprising one or more of iron (III) sulfate,
iron (III) chloride, iron (III) acetate, and hydrates thereof.
5. The electrolyte solution of claim 1, wherein the trivalent
chromium salt is selected from a chromium (III) halide, a chromium
(III) sulfate, or a combination thereof.
6. The electrolyte solution of claim 1, wherein the oxalate
compound is selected from sodium oxalate, potassium oxalate, an
acid of oxalate, or a combination thereof.
7. The electrolyte solution of claim 1, wherein the alkali metal
sulfate is selected from sodium sulfate, potassium sulfate, or a
combination thereof.
8. The electrolyte solution of claim 1, wherein the alkali metal
halide is selected from sodium fluoride, potassium fluoride, or a
combination thereof.
9. The electrolyte solution of claim 1, wherein a pH of the
electrolyte solution is in a range from about 1 to about 4.
10. The electrolyte solution of claim 1, further comprising sodium
lauryl sulfate, sodium lauryl ether sulfate, or a combination
thereof.
11. A method of chrome plating on a substrate using an electrolyte
solution, comprising: introducing a cathode and an anode into an
electrolyte solution comprising a trivalent chromium salt, an
oxalate compound, an iron salt, an aluminum sulfate, an alkali
metal sulfate, and an alkali metal halide; and passing a current
between the anode and the cathode through the electrolyte solution
to deposit a chromium layer on the substrate.
12. The method of claim 11, wherein the cathode is a steel
substrate, a copper substrate, a brass substrate, a nickel
substrate, a copper-coated substrate, or a nickel-coated
substrate.
13. The method of claim 11, wherein the anode is a platinum
material, platinized titanium material, or a carbonaceous electrode
material.
14. The method of claim 11, wherein the current has a current
density in a range from about 10 to about 60 mA/cm.sup.2 by passing
direct current between the anode and the cathode.
15. The method of claim 14, wherein the current density has a
current density in a range from about 20 to about 40
mA/cm.sup.2.
16. The method of claim 14, wherein the electrolyte solution is
maintained at a temperature in a range from about 20 degrees
Celsius and about 60 degrees Celsius.
17. The method of claim 11, further comprising adjusting a pH of
the electrolyte solution to a pH in a range from about 1.5 to about
4.
18. A substrate comprising: a chromium-iron alloy coating having a
chromium content in a range of about 40 wt. % to about 90 wt. %, an
iron content in a range of about 8 wt. % to about 18 wt. %, and a
carbon content in a range of about 5 wt. % to about 50 wt. %.
19. The substrate of claim 18, wherein the substrate comprises one
or more of steel, copper, brass, or nickel.
20. The substrate of claim 19, wherein the chromium-iron alloy
coating has a thickness of from about 1 micron and about 100
microns.
Description
FIELD
[0001] The present disclosure provides electrolyte solutions for
electrodeposition of chromium alloys, methods of forming
electrolyte solutions, and methods of electrodepositing chromium
alloys.
BACKGROUND
[0002] Chrome plating is an electroplating process that provides a
chrome coating on a substrate. Hard chrome plating provides a
chrome coating having a thickness typically about 10 microns or
greater, thereby providing hardness and wear resistance to the
coated substrate. The other type of chrome plating is decorative
chrome plating, which provides a chrome coating having a thickness
typically ranging from about 0.1 to about 0.5 microns. Chrome
plating is often performed using baths containing chromic acid and
catalysts based on fluorides, sulfates or organic acids. Chromic
acid has chromium in its hexavalent form, chromium (VI), which is
not environmentally preferred and expensive to dispose of.
[0003] Trivalent chromium, which has benign properties and lower
waste treatment costs, is one alternative to hexavalent chromium.
There has been some success implementing trivalent chromium for
thin, decorative plating, however, there is still difficulty in
achieving thicker or functional coatings. In addition, trivalent
chromium-based baths used in decorative plating typically contain
boric acid as a buffering agent.
[0004] Thus, there is a need for improved chrome plating methods
and formulations of solutions used in chrome plating.
SUMMARY
[0005] The present disclosure provides electrolyte solutions for
electrodeposition of chromium alloys, methods of forming
electrolyte solutions, and methods of electrodepositing chromium
alloys.
[0006] At least one electrolyte solution for electroplating
includes a trivalent chromium salt, an oxalate compound, an iron
salt, an aluminum sulfate, an alkali metal sulfate, and an alkali
metal halide.
[0007] At least one electrolyte solution for electroplating
includes a trivalent chromium salt in an amount ranging from about
0.3 moles per liter to about 0.9 moles per liter of the electrolyte
solution. The electrolyte solution further includes an oxalate
compound in an amount ranging from about 0.2 moles per liter to
about 1.2 moles per liter of the electrolyte solution. The
electrolyte solution further includes an iron salt in an amount
ranging from about 0.005 moles per liter to about 0.2 moles per
liter of the electrolyte solution. The electrolyte solution further
includes an aluminum sulfate in an amount ranging from about 0.05
moles per liter to about 0.5 moles per liter. The electrolyte
solution further includes an alkali metal sulfate in an amount
ranging from about 0.1 moles per liter to about 2.0 moles per liter
of the electrolyte solution. The electrolyte solution further
includes an alkali metal halide in an amount ranging from about 0.1
moles per liter to about 0.5 moles per liter of the electrolyte
solution.
[0008] At least one method of chrome plating on a substrate using
an electrolyte solution is provided. The method includes dissolving
in an aqueous medium a trivalent chromium salt in an amount ranging
from about 0.3 moles per liter to about 0.9 moles per liter of the
electrolyte solution. The method further includes dissolving an
oxalate compound in an amount ranging from about 0.2 moles per
liter to about 1.2 moles per liter of the electrolyte solution. The
method further includes dissolving iron salt in an amount ranging
from about 0.005 moles per liter to about 0.2 moles per liter of
the electrolyte solution. The method further includes dissolving
aluminum sulfate in an amount ranging from about 0.05 moles per
liter to about 0.5 moles per liter. The method further includes
dissolving an alkali metal sulfate in an amount ranging from about
0.1 moles per liter to about 2.0 moles per liter of the electrolyte
solution. The method further includes dissolving an alkali metal
halide in an amount ranging from about 0.1 moles per liter to about
0.5 moles per liter of the electrolyte solution. The method further
comprises passing a current between a cathode and an anode through
the electrolyte solution to deposit a chromium-iron alloy on a
substrate.
[0009] At least one method of chrome plating on a substrate using
an electrolyte solution is provided. The method includes
introducing a cathode and an anode into an electrolyte solution
comprising a trivalent chromium salt, an oxalate compound, an iron
salt, an aluminum sulfate, an alkali metal sulfate, and an alkali
metal halide. The method further includes passing a current between
the anode and the cathode through the electrolyte solution to
deposit a chromium-iron alloy layer on the substrate.
[0010] At least one substrate including a chromium-iron alloy
coating is provided. The chromium-iron alloy coating has a chromium
content in a range of about 40 wt. % to about 90 wt. %, an iron
content in a range of about 8 wt. % to about 18 wt. %, and a carbon
content in the range of about 5 wt. % to about 50 wt. %.
[0011] The features, functions, and advantages that have been
discussed can be achieved independently in various aspects or can
be combined in yet other aspects, further details of which can be
seen with reference to the following description and drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0012] So that the manner in which the above-recited features of
the present disclosure can be understood in detail, a more
particular description of the disclosure briefly summarized above
can be had by reference to aspects, some of which are illustrated
in the appended drawings. It is to be noted, however, that the
appended drawings illustrate only typical aspects of this
disclosure and are therefore not to be considered limiting of its
scope, for the disclosure can admit to other equally effective
aspects.
[0013] FIG. 1 is a flow diagram illustrating a method for forming
an electrolyte solution according to one or more aspects of the
present disclosure;
[0014] FIG. 2 is a flow diagram illustrating a method for forming a
chromium alloy coating on a substrate by electrodeposition
according to one or more aspects of the present disclosure;
[0015] FIG. 3 is an image of chromium-iron alloy plated substrates
formed by the process of FIG. 2, each plated at a different current
density;
[0016] FIG. 4 is an image of chromium-iron alloy plated substrates
formed by the process of FIG. 2, each plated at a different pH;
[0017] FIG. 5 is an image of chromium-iron alloy plated substrates
formed by the process of FIG. 2, each plated at a different current
density;
[0018] FIG. 6 is an image of chromium-iron alloy plated substrates
formed by the process of FIG. 2, each plated at a different pH;
[0019] FIG. 7 is an image of chromium-iron alloy plated substrates
formed by the process of FIG. 2, each plated at a different current
density;
[0020] FIG. 8 is an image of chromium-iron alloy plated substrates
formed by the process of FIG. 2, each plated at a different pH;
and
[0021] FIG. 9 is an image of chromium-iron alloy plated substrates
formed by the process of FIG. 2, each plated at a different
temperature.
[0022] To facilitate understanding, identical reference numerals
have been used, wherever possible, to designate identical elements
that are common to the figures. Additionally, elements of one
aspect can be advantageously adapted for utilization in other
aspects described herein.
DETAILED DESCRIPTION
[0023] In accordance with aspects of the present disclosure,
various methods and formulations are provided for chrome plating a
substrate using direct current and a trivalent chromium solution
that does not include boric acid, while still resulting in a
chromium layer (e.g., a chromium coating) formed on the substrate
that can be structurally robust and reliable, yet cost-effective.
Thus, the methods and formulations described herein can
advantageously be used for hard chrome plating to form hard
chromium layers (e.g., a robust, functional chromium layer of
greater than 10 microns). However, the present disclosure is not
limited to hard chrome plating and the methods and formulations
described herein can also be advantageously used to effectively and
efficiently perform decorative chrome plating, which forms
decorative chromium layers (e.g., a chromium layer ranging from
0.25 micron to 1.0 micron).
[0024] The present disclosure further provides electrolyte
solutions for electrodeposition of chromium-iron alloys and methods
of forming chromium-iron alloys. In at least one aspect,
electrolyte solutions of the present disclosure are aqueous. In at
least one aspect, an electrolyte solution comprises an iron salt,
such as, for example, ferrous sulfate or ferric chloride. It has
been discovered that one or more of these iron salts present in an
electrolyte solution provides deposition of thick chromium-iron
alloy layers on a substrate, such as a steel substrate without the
use of hexavalent chromium and pulsed plating. Electrolyte
solutions of the present disclosure further comprise at least one
complexing agent such as an oxalate compound, for example, sodium
oxalate, which forms complexes with trivalent chromium ions as well
as ferrous ions.
[0025] Electrolyte solutions of the present disclosure provide
controllable chromium-iron alloy deposition on a substrate. In at
least one aspect, a substrate is a steel substrate, copper
substrate, brass substrate, copper-coated substrate, nickel-coated
substrate, or other metal or metal alloy-containing substrate. In
at least one aspect, the electrolyte solutions of the present
disclosure when used at temperatures in a range of about 30.degree.
C. to about 60.degree. C. in at a pH in a range of about 2 to about
4 provide satisfactorily hard chromium-iron alloy deposits that are
considered comparable to conventional hexavalent chromium based
coatings. In at least one aspect, iron content of a chromium-iron
alloy of the present disclosure is from about 1 wt. % iron to about
20 wt. % iron based on the total weight of chromium and iron in the
alloy.
[0026] Chromium-iron alloy coatings of the present disclosure
provide similar hardness and wear resistance for substrates, such
as steel substrates, to that of conventional hexavalent hard chrome
plated substrates. The chromium-iron alloys of the present
disclosure can be disposed on components of aircraft, spacecraft,
watercraft, engine and blown-flap, exhaust-washed structures,
warm-structure components for high-performance supersonic,
hypersonic, and space re-entry vehicle structures, automobile
parts, architectural structures such as steel bridges and
propulsion structures such as power-generation turbines, vehicle
engines, alternative-energy applications, and related technologies.
As one specific example, alloys of the present disclosure can be
disposed on steel-based landing gears and/or a bottom surface of an
aircraft.
[0027] In at least one aspect, chromium-iron coatings of the
present disclosure are formed using a single bath technique. The
deposition vessel is a glass beaker at a lab scale or large
polypropylene tanks for plating on a commercial scale. In at least
one aspect, the deposition vessel contains an electrolyte solution
that is prepared by mixing all ingredients of the electrolyte
solution concurrently or in a stepwise manner starting with
chromium salts and complexing agents followed by iron salts. The
anode (e.g., graphite) is introduced into the beaker containing
electrolyte solution, as described in more detail below. The
deposition process is modulated by applying direct current, which
creates the chromium-iron alloy coating. The thickness of the
chromium-iron alloy coating can be controlled by the duration of
the direct current applied to the electrolyte solution electrodes.
In at least one aspect, the total thickness of a chromium-iron
alloy coating is from about 1 micron to about 100 microns, such as
from about 10 microns to about 50 microns, such as from about 20
microns to about 40 microns, for example about 30 microns.
[0028] Varying the thickness and composition of a chromium-iron
alloy coating can be controlled by current density and time scale
of a deposition process of the present disclosure.
[0029] Electrolyte solutions of the present disclosure comprise a
metal salt. As used herein, metal salt can include anhydrous and
/or hydrate forms of a metal salt. In at least one aspect, metal
salts include one or more of a trivalent chromium salt and an iron
salt. Electrolyte solutions of the present disclosure further
comprise at least one complexing agent such as an alkali metal
oxalate compound, for example, sodium oxalate or potassium oxalate.
Complexing agents, such as alkali metal oxalate compounds,
coordinate to iron ions in an electrolyte solution and promote
controllable iron deposition on a substrate upon application of a
current density to the electrolyte solution.
[0030] Electrolyte solutions of the present disclosure further
comprise at least one buffering agent such as an aluminum salt, for
example, aluminum sulfate or an aluminum halide. Buffering agents
of the present disclosure maintain a desirable pH of the
electrolyte solution and do not substantially interfere with
chromium and iron deposition on a substrate, as described in more
detail below.
[0031] Electrolyte solutions of the present disclosure further
comprise at least one ionic conductivity control agent such as an
alkali metal salt, for example, sodium sulfate or potassium
sulfate. Ionic conductivity control agents of the present
disclosure maintain a desirable conductivity of the electrolyte
solution and do not substantially interfere with chromium and iron
deposition on a substrate.
[0032] Electrolyte solutions of the present disclosure further
comprise at least one alkali metal halide, for example, sodium
fluoride or potassium fluoride. Alkali metal halides of the present
disclosure provide the electrolyte solution with wetting and
etching properties, and can help chromium adhesion during chrome
plating.
[0033] Optionally, electrolyte solutions of the present disclosure
further comprise at least one surfactant, for example, sodium
lauryl sulfate, sodium lauryl ether sulfate, or potassium lauryl
sulfate. Surfactants of the present disclosure reduce pitting and
gas generation during chrome plating.
[0034] In at least one aspect, the pH of electrolyte solutions of
the present disclosure is between about 1 and about 6, such as
between about 1.5 and about 4, for example the pH is 2 or 4. In at
least one aspect, the pH of electrolyte solutions of the present
disclosure are controlled by addition of one or more bases, such as
a sodium hydroxide (NaOH) solution, to increase the pH of the
solution or addition of one or more acids, such as a sulfuric acid
(H.sub.2SO.sub.4) solution, to decrease the pH of the solution.
Chromium salts, iron salts, complexing agents, buffering agents,
acids, and bases can be obtained from any suitable commercial
source, such as MERCK-India or Sigma-Aldrich Co. LLC of St. Louis,
Mo.
[0035] FIG. 1 is a flow diagram illustrating a method 100 for
forming an electrolyte solution according to one or more aspects of
the present disclosure. As shown in FIG. 1, at operation 110,
method 100 includes dissolving a trivalent chromium salt in a
medium such as water or an aqueous solution to form a first
electrolyte solution. The trivalent chromium salt is a trivalent
chromium source. In at least one aspect, the trivalent chromium
salt includes a chromium (III) halide, chromium (III) sulfate
(e.g., Cr.sub.2(SO.sub.4).sub.3,
Cr.sub.2(SO.sub.4).sub.3.12H.sub.2O, and/or other chromium (III)
sulfates), and/or other chromium (III) salts. The chromium (III)
halide can include, for example, chromium (III) chloride (e.g.,
CrCl.sub.3, CrCl.sub.3.5H.sub.2O, CrCl.sub.3.6H.sub.2O, and/or
other chromium (III) chlorides).
[0036] In at least one aspect, the concentration of the trivalent
chromium salt in the electrolyte of the present disclosure ranges
from about 0.1 moles per liter (mol/L) to about 1 mol/L, such as in
a range from about 0.3 mol/L to about 0.9 mol/L, such as in a range
from about 0.2 mol/L to about 0.7 mol/L, such as in a range from
about 0.4 mol/L to about 0.7 mol/L of the electrolyte solution, for
example, in a range from about 0.5 mol/L to about 0.6 mol/L. In at
least one aspect, the amount of the trivalent chromium salt that is
dissolved is about 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5
mol/L, 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 0.9 mol/L, or 1 mol/L of
the electrolyte solution, where any value can form an upper end
point or a lower end point, as appropriate. At concentrations above
1 mol/L, it can become difficult to dissolve the trivalent chromium
salt in the electrolyte leading to solubility issues.
[0037] In at least one aspect, the trivalent chromium salt is
dissolved by stirring at ambient temperature, at room temperature,
at about 25.degree. C., or at a temperature ranging from about
10.degree. C. to about 40.degree. C., for example, from about
20.degree. C. to about 30.degree. C. In at least one aspect, the
temperature at which operation 110. is performed can be about
10.degree. C., 15.degree. C., 20.degree. C., 25.degree. C.,
30.degree. C., 35.degree. C., or 40.degree. C., where any value can
form an upper end point or a lower end point, as appropriate. In at
least one aspect, the stirring can be performed for about 5
minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30
minutes, where any value can form an upper end point or a lower end
point, as appropriate, or until all the trivalent chromium salt has
been dissolved.
[0038] At operation 120, the method 100 further includes dissolving
an oxalate compound for example, in water or an aqueous solution
(such as the first solution) to form an electrolyte solution, such
as a second electrolyte solution. The oxalate compound includes
oxalate, which can function as a complexing agent. In at least one
aspect, the oxalate compound includes an alkali metal oxalate
(e.g., sodium oxalate (Na.sub.2C.sub.2O.sub.4), a potassium oxalate
(K.sub.2C.sub.2O.sub.4), and/or other alkali metal oxalates) and/or
an acid of oxalate (e.g., oxalic acid (H.sub.2C.sub.2O.sub.4)
and/or other acids of oxalate).
[0039] In at least one aspect, the concentration of the oxalate
compound in the electrolyte of the present disclosure is in a range
from about 0.1 mol/L to about 2.0 mol/L, such as in a range from
about 0.2 mol/L to about 1.2 mol/L such as in a range from about
0.1 mol/L to about 0.9 mol/L, such as in a range from about 0.2
mol/L to about 0.7 mol/L, such as in a range from about 0.4 mol/L
to about 0.7 mol/L of the electrolyte solution, for example, in a
range from about 0.5 mol/L to about 0.6 mol/L. In at least one
aspect, the amount of the oxalate compound that is dissolved is
about 0.1 mol/L, 0.2 mol/L, 0.4 mol/L, 0.6 mol/L, 0.8 mol/L, 1.0
mol/L, 1.2 mol/L, 1.4 mol/L, 1.6 mol/L, 1.8 mol/L, or 2.0 mol/L of
the electrolyte solution, where any value can form an upper end
point or a lower end point, as appropriate.
[0040] In at least one aspect, to dissolve the oxalate compound and
form a complex of oxalate and trivalent chromium, the oxalate
compound is put in solution (e.g., the solution resulting from
operation 110. or another operation performed prior to operation
120), the solution can be heated to a higher temperature ranging
from about 70.degree. C. to about 80.degree. C., and the solution
can be stirred for about 1 hour to about 3 hours. In at least one
aspect, the solution is cooled (e.g., to ambient temperature, to
room temperature, to about 25.degree. C., or to a temperature
ranging from about 20.degree. C. to about 30.degree. C.).
Alternatively, the oxalate compound can be dissolved without
heating, in which case a complex of oxalate and trivalent chromium
is formed in 3 to 4 days. Advantageously, heating the solution to a
temperature ranging from about 70.degree. C. to about 80.degree. C.
at operation 120 allows the electrolyte solution to be prepared
more quickly. In at least one aspect, the stirring is performed for
about 1 hour, 1 hour and 15 minutes, 1 hour and 30 minutes, 1 hour
and 45 minutes, 2 hours, 2 hours and 15 minutes, 2 hours and 30
minutes, 2 hours and 45 minutes, or 3 hours, where any value can
form an upper end point or a lower end point, as appropriate.
Further, in at least one aspect, the temperature at which operation
120 is performed is about 50.degree. C., 55.degree. C., 60.degree.
C., 65.degree. C., 70.degree. C., 75.degree. C., or 80.degree. C.,
where any value can form an upper end point or a lower end point,
as appropriate.
[0041] At operation 130, the method 100 further includes dissolving
an iron salt, for example, in water or an aqueous solution (such as
the second electrolyte solution) to form an electrolyte solution
(e.g., a third electrolyte solution). In at least one aspect, the
iron salt is a divalent iron salt, a trivalent iron salt, or a
combination thereof. In at least one aspect, the iron salt is
ferrous sulfate heptahydrate, ferric chloride, or a combination
thereof. In at least one aspect, the iron salt is a divalent iron
salt. In at least one aspect, the divalent iron salt includes iron
(II) sulfate, iron (II) chloride, iron (II) acetate, and/or other
divalent iron salts. Each of these divalent iron salts can include
its respective hydrated forms. For example, iron (II) sulfate has
the formula FeSO.sub.4.xH.sub.2O, where x is a whole number (e.g.,
0, 1, 2, 4, 5, 6, or 7). Accordingly, in at least one aspect, iron
(II) sulfate is anhydrous iron (II) sulfate, iron (II) sulfate
monohydrate, iron (II) sulfate dihydrate, iron (II) sulfate
tetrahydrate, iron (II) sulfate pentahydrate, iron (II) sulfate
hexahydrate, iron (II) sulfate heptahydrate, or iron (II) sulfate
with another hydration state. In at least one aspect, the iron salt
is a trivalent iron salt. In at least one aspect, the trivalent
iron salt includes iron (III) sulfate, iron (III) chloride, iron
(III) acetate, and/or other trivalent iron salts. Each of these
trivalent iron salts can include its respective hydrated forms. For
example, iron (III) sulfate has the formula
Fe.sub.2(SO.sub.4).sub.3.xH.sub.2O, where x is a whole number
(e.g., 0, 1, 2, 4, 5, 6, or 7). Accordingly, in at least one
aspect, iron (III) sulfate is anhydrous iron (III) sulfate, iron
(III) sulfate monohydrate, iron (III) sulfate dihydrate, iron (III)
sulfate tetrahydrate, iron (III) sulfate pentahydrate, iron (III)
sulfate hexahydrate, iron (III) sulfate heptahydrate, or iron (III)
sulfate with another hydration state. In a further example, iron
(III) chloride has the formula FeCl.sub.3.xH.sub.2O, where x is a
whole number (e.g., 0, 1, 2, 4, 5, 6, or 7). Accordingly, in at
least one aspect, iron (III) chloride is anhydrous iron (III)
chloride, iron (III) chloride monohydrate, iron (III) chloride
dihydrate, iron (III) chloride tetrahydrate, iron (III) chloride
pentahydrate, iron (III) chloride hexahydrate, iron (III) chloride
heptahydrate, or iron (III) chloride with another hydration
state.
[0042] In at least one aspect, the concentration of the iron salt
in the electrolyte of the present disclosure ranges from about
0.005 mol/L to about 0.2 mol/L, such as in a range from about 0.01
mol/L to about 0.2 mol/L, such as in a range from about 0.02 mol/L
to about 0.2 mol/L of the electrolyte solution, for example, in a
range from about 0.1 mol/L to about 0.2 mol/L. In at least one
aspect, the amount of the iron salt that is dissolved is about
0.005 mol/L, 0.01 mol/L, 0.02 mol/L, 0.03 mol/L, 0.04 mol/L, 0.05
mol/L, 0.06 mol/L, 0.07 mol/L, 0.08 mol/L, 0.09 mol/L, 0.1 mol/L,
or 0.2 mol/L of the electrolyte solution, where any value can form
an upper end point or a lower end point, as appropriate. It has
been found by the inventors that at concentrations above 0.2 mol/L,
the deposited chromium-iron alloy coating becomes soft and can also
be more susceptible to corrosion.
[0043] In at least one aspect, the iron salt is dissolved by
stirring at ambient temperature, at room temperature, at about
25.degree. C., or at a temperature ranging from about 20.degree. C.
to about 30.degree. C. In at least one aspect, the stirring is
performed for about 5 minutes, 10 minutes, 15 minutes, 20 minutes,
25 minutes, or 30 minutes, where any value can form an upper end
point or a lower end point, as appropriate, or until all the iron
salt has been dissolved. In at least one aspect, the temperature at
which operation 130 is performed is about 10.degree. C., 15.degree.
C., 20.degree. C., 25.degree. C., 30.degree. C., 35.degree. C., or
40.degree. C., where any value can form an upper end point or a
lower end point, as appropriate.
[0044] At operation 140, the method 100 further includes dissolving
a metal salt, for example, in water or an aqueous solution (such as
the third electrolyte solution) to form an electrolyte solution
(e.g., a fourth electrolyte solution). The metal salt is a metal
ion source that dissolves to provide metal ions such as aluminum
ions, which can function as a buffer and can provide ionic strength
due to the high valence of the metal ion in solution (e.g.,
Al.sup.3+). In at least one aspect, the metal salt includes a group
13 metal salt such as an aluminum salt (e.g., aluminum sulfate
(Al.sub.2(SO.sub.4).sub.3), an aluminum halide such as aluminum
chloride (Al Cl.sub.3), and/or other aluminum salts) and/or other
metal salts.
[0045] In at least one aspect, the concentration of the metal salt
in the electrolyte of the present disclosure ranges from about 0.01
mol/L to about 1.0 mol/L, such as in a range from about 0.05 mol/L
to about 0.8 mol/L, such as in a range from about 0.1 mol/L to
about 0.7 mol/L, such as in a range from about 0.2 mol/L to about
0.5 mol/L of the electrolyte solution, for example, in a range from
about 0.2 mol/L to about 0.3 mol/L. In at least one aspect, the
amount of the metal salt that is dissolved is about 0.01 mol/L,
0.05 mol/L, 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L,
0.6 mol/L, 0.8 mol/L, or 1.0 mol/L of the electrolyte solution,
where any value can form an upper end point or a lower end point,
as appropriate. At concentrations above 1.0 mol/L, it can become
difficult to dissolve the metal salt in the electrolyte leading to
solubility issues.
[0046] In at least one aspect, the metal salt is dissolved by
stirring at ambient temperature, at room temperature, at about
25.degree. C., or at a temperature ranging from about 20.degree. C.
to about 30.degree. C. In at least one aspect, the stirring is
performed for about 5 minutes, 10 minutes, 15 minutes, 20 minutes,
25 minutes, or 30 minutes, where any value can form an upper end
point or a lower end point, as appropriate, or until all the metal
salt has been dissolved. In at least one aspect, the temperature at
which operation 140 is performed is about 10.degree. C., 15.degree.
C., 20.degree. C., 25.degree. C., 30.degree. C., 35.degree. C., or
40.degree. C., where any value can form an upper end point or a
lower end point, as appropriate.
[0047] At operation 150, the method 100 further includes dissolving
an alkali metal salt, for example, in water or an aqueous solution
(such as the fourth electrolyte solution) to form an electrolyte
solution (e.g., a fifth electrolyte solution). The alkali metal
salt can increase the conductivity of the electrolyte solution. In
at least one aspect, the alkali metal salt includes an alkali metal
sulfate (e.g., sodium sulfate (Na.sub.2SO.sub.4), potassium sulfate
(K.sub.2SO.sub.4), and/or other alkali metal sulfates).
[0048] In at least one aspect, the concentration of the alkali
metal salt in the electrolyte of the present disclosure is in a
range from about 0.1 mol/L to about 2.0 mol/L, such as in a range
from about 0.5 mol/L to about 2.0 mol/L such as in a range from
about 1.0 mol/L to about 1.5 mol/L, for example, in a range from
about 1.3 mol/L to about 1.4 mol/L. In at least one aspect, the
amount of the oxalate compound that is dissolved is about 0.1
mol/L, 0.2 mol/L, 0.4 mol/L, 0.6 mol/L, 0.8 mol/L, 1.0 mol/L, 1.2
mol/L, 1.4 mol/L, 1.6 mol/L, 1.8 mol/L, or 2.0 mol/L of the
electrolyte solution, where any value can form an upper end point
or a lower end point, as appropriate. At concentrations above 2.0
mol/L, it can become difficult to dissolve the alkali metal salt in
the electrolyte leading to solubility issues.
[0049] In at least one aspect, the alkali metal salt is dissolved
by stirring at ambient temperature, at room temperature, at about
25.degree. C., or at a temperature ranging from about 10.degree. C.
to about 40.degree. C., for example, from about 20.degree. C. to
about 30.degree. C. In at least one aspect, the temperature at
which operation 150 is performed can be about 10.degree. C.,
15.degree. C., 20.degree. C., 25.degree. C., 30.degree. C.,
35.degree. C., or 40.degree. C., where any value can form an upper
end point or a lower end point, as appropriate. In at least one
aspect, the stirring can be performed for about 5 minutes, 10
minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes, where
any value can form an upper end point or a lower end point, as
appropriate, or until all the alkali metal salt has been dissolved.
In at least one aspect, the alkali metal salt is dissolved by
stirring for 15 minutes at ambient temperature, at room
temperature, at about 25.degree. C.
[0050] At operation 160, the method 100 further includes dissolving
an alkali metal halide, for example, in water or an aqueous
solution (such as the fifth electrolyte solution) to form an
electrolyte solution (e.g., a sixth electrolyte solution). The
alkali metal halide can provide the electrolyte solution with
wetting and etching properties, and can help chromium adhesion
during chrome plating. In at least one aspect, the alkali metal
halide includes an alkali metal fluoride (e.g., sodium fluoride
(NaF), potassium fluoride (KF), and/or other alkali metal
fluorides) and/or other alkali metal halides.
[0051] In at least one aspect, the concentration of the alkali
metal halide in the electrolyte of the present disclosure is in a
range from about 0.1 mol/L to about 1.0 mol/L, such as in a range
from about 0.1 mol/L to about 0.5 mol/L such as in a range from
about 0.2 mol/L to about 0.5 mol/L, for example, in a range from
about 0.3 mol/L to about 0.4 mol/L. In at least one aspect, the
amount of the oxalate compound that is dissolved is about 0.1
mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, 0.8
mol/L, or 1.0 mol/L of the electrolyte solution, where any value
can form an upper end point or a lower end point, as appropriate.
At concentrations above 1.0 mol/L, it can become difficult to
dissolve the alkali metal halide in the electrolyte leading to
solubility issues.
[0052] In at least one aspect, the alkali metal halide is dissolved
by stirring at ambient temperature, at room temperature, at about
25.degree. C., or at a temperature ranging from about 10.degree. C.
to about 40.degree. C., for example, from about 20.degree. C. to
about 30.degree. C. In at least one aspect, the temperature at
which operation 160 is performed is about 10.degree. C., 15.degree.
C., 20.degree. C., 25.degree. C., 30.degree. C., 35.degree. C., or
40.degree. C., where any value can form an upper end point or a
lower end point, as appropriate. In at least one aspect, the
stirring is performed for about 5 minutes, 10 minutes, 15 minutes,
20 minutes, 25 minutes, or 30 minutes, where any value can form an
upper end point or a lower end point, as appropriate, or until all
the alkali metal halide has been dissolved. In at least one aspect,
the alkali metal halide is dissolved by stirring for 15 minutes at
ambient temperature, at room temperature, at about 25.degree.
C.
[0053] Optionally, at operation 170, the method 100 further
includes dissolving a surfactant, for example, in water or an
aqueous solution (such as the sixth electrolyte solution) to form
an electrolyte solution (e.g., a seventh electrolyte solution). The
surfactant can prevent or reduce pitting and reduce gas generation
(e.g., chlorine gas, hydrogen gas, etc.) during chrome plating. In
at least one aspect, the surfactant includes sodium lauryl sulfate
(NaC.sub.12H.sub.25SO.sub.4), sodium lauryl ether sulfate
(CH.sub.3(CH.sub.2).sub.11(OCH.sub.2CH.sub.2).sub.nOSO.sub.3Na),
potassium lauryl sulfate (KC.sub.12H.sub.25 SO.sub.4), and/or other
surfactants.
[0054] In at least one aspect, the concentration of the surfactant
in the electrolyte of the present disclosure is in a range from
about 0.0001 mol/L to about 0.01 mol/L. In at least one aspect, the
amount of the surfactant that is dissolved can be about 0.0001
mol/L, 0.0002 mol/L, 0.0004 mol/L, 0.0006 mol/L, 0.0008 mol/L,
0.0010 mol/L, 0.0020 mol/L, 0.0040 mol/L, 0.0060 mol/L, 0.0080
mol/L, or 0.0100 mol/L of the electrolyte solution, where any value
can form an upper end point or a lower end point, as appropriate.
For example, in at least one aspect, the amount of sodium lauryl
sulfate, sodium lauryl ether sulfate, or potassium lauryl sulfate
is in a range from about 0.1 g to about 1 g per liter of the
electrolyte solution. At concentrations above 0.01 mol/L, the
surfactant can cause excessive foaming of the bath and nonuniform
deposition.
[0055] Optionally, at operation 180 the method 100 further includes
adjusting the pH of the electrolyte solution using one or more
aqueous acid solutions or aqueous base solutions, such as potassium
hydroxide (KOH), sodium hydroxide (NaOH), and/or sulfuric acid
(H.sub.2SO.sub.4). The volume of aqueous acid solution or aqueous
base solution added to the electrolyte solution is sufficiently
small such that the concentration of other components (complexing
agents, buffering agents, etc.) of the electrolyte solution is not
substantially affected. Alternatively, solid potassium hydroxide
and/or solid sodium hydroxide is added directly to the electrolyte
solution and/or concentrated sulfuric acid is added directly to the
electrolyte solution. In at least one aspect, the pH of the
electrolyte solution is adjusted to a target pH from about 1 to
about 7, such as from about 1 to about 5, such as from about 1.5 to
about 4, for example 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5. In at
least one aspect, the pH of an electrolyte solution of the present
disclosure is adjusted before passing a current through the
electrolyte solution (as described in more detail below). In at
least one aspect, the pH of an electrolyte solution of the present
disclosure is maintained at a target pH or a target pH range during
the passing of a current through the electrolyte solution.
[0056] Optionally, at operation 190, time is provided to reach
equilibrium state. In at least one aspect, the solution is left to
stand for a time ranging from 1 hour to 2 days to reach the
equilibrium state. The time provided to reach the equilibrium state
can be about 1 hour, 3 hours, 6 hours, 9 hours, 12 hours, 15 hours,
18 hours, 21 hours, 24 hours, 27 hours, 30 hours, 33 hours, 36
hours, 39 hours, 42 hours, 45 hours, or 48 hours, where any value
can form an upper end point or a lower end point, as
appropriate.
[0057] In at least one aspect, the method 100 is performed in the
order presented. Alternatively, the method 100 is performed in a
different order. In at least one aspect, some operations are
performed in order while other operations are performed in a
different order.
[0058] For example, operations 110 and 120 are performed in order,
while operations 130, 140, 150, 160, 170, 180, and 190 are
performed in a different order after operations 110 and 120. In
another example, operations 110 and operations 120 are performed in
a different order while operations 130, 140, 150, 160, 170, 180,
and 190 are performed in order. In another example, operations 110,
120, 130, 140, 150, and 160 are performed in order, while
operations 170, 180, and 190 are performed in a different order. A
group of operations can be performed before another group of
operations. For example, operations 110 and 120 can be performed in
any order, and after operations 110 and 120 are performed,
operations 130, 140, 150, and 160 are performed in any order. Other
orders are contemplated as one skilled in the art will appreciate.
Further, one or more of operations 170, 180, and 190 are omitted in
some aspects.
[0059] FIG. 2 is a flow diagram illustrating a method 200 for
forming a chromium alloy coating on a substrate by
electrodeposition according to one or more aspects of the present
disclosure. At operation 210, an electrolyte solution is prepared,
such as by the method 100 of FIG. 1. At operation 220, the method
200 further includes adjusting and/or maintaining a pH of the
electrolyte solution at a target pH or a target pH range. In at
least one aspect, the target pH is a pH ranging from about 1 to
about 4. The pH can be maintained at about 1, 1.2, 1.4, 1.5, 1.6,
1.8, 2, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, or 4.0, where
any value can form an upper end point or a lower end point, as
appropriate.
[0060] At operation 230, the method 200 further includes adjusting
and/or maintaining a temperature of an electrolyte solution, such
as the electrolyte solution formed by operation 210. In at least
one aspect, the temperature is adjusted to/maintained at a target
temperature of from about 20.degree. C. to about 70.degree. C.,
such as from about 20.degree. C. to about 40.degree. C., such as
from about 20.degree. C. to about 35.degree. C., for example
20.degree. C., 25.degree. C., or 30.degree. C., using any suitable
heating or cooling apparatus. In at least one aspect, the
temperature of the electrolyte solution is adjusted before passing
a current through the electrolyte solution. In at least one aspect,
the temperature of the electrolyte solution is maintained during
the passing of a current through the electrolyte solution to
maintain the appearance of a deposited layer. Maintaining the
temperature within a desirable range promotes obtaining
reproducible results in terms of appearance and alloy
composition.
[0061] At operation 240, the method further includes introducing a
cathode and an anode into the electrolyte solution, the cathode
including the substrate and at operation 250, passing a current
between the cathode and the anode through the electrolyte solution
to deposit a chromium alloy onto the cathodic substrate. In at
least one aspect, the cathodic substrate is, for example, a steel
substrate, a ferrous alloy substrate, a copper substrate, a brass
substrate, a nickel substrate, a copper-coated substrate (e.g.,
copper-coated steels or copper-coated ferrous alloys), or a
nickel-coated substrate (e.g., nickel-coated steels or
nickel-coated ferrous alloys).
[0062] In at least one aspect, the anode includes a carbonaceous
electrode material. For example, the carbonaceous anode can be a
graphite anode or other anode that includes carbon. In at least one
aspect, the graphite anode is used for chloride-based electrolyte
solutions (e.g., electrolyte solutions that include one or more
compounds with chloride such as chromium (III) chloride),
sulfate-based electrolyte solutions (e.g., electrolyte solutions
that include one or more compounds with sulfate such as chromium
(III) sulfate), or chloride and sulfate-based electrolyte solutions
(e.g., electrolyte solutions that include one or more compounds
with chloride and one or more other compounds with sulfate).
Advantageously, the graphite anode or other carbonaceous anode
minimizes gas evolution and formation of undesirable byproducts, as
well as facilitating a desirable deposition rate (e.g., ranging
from about 1 micron to about 2 microns per minute). Alternatively,
a platinum anode or a platinized titanium anode can be used for
sulfate-based electrolyte solutions (e.g., electrolyte solutions
that include one or more compounds with sulfate such as chromium
(III) sulfate). For example, the platinum anode or platinized
titanium anode can be used when the electrolyte solution does not
include compounds with chloride such that chlorine gas is not
produced, or when the electrolyte solution has less chloride such
that less chlorine gas is generated (e.g., there is no need to
reduce the generation of chlorine gas using a carbonaceous
anode).
[0063] In at least one aspect, passing a current between the
cathode and the anode is performed using direct current. In at
least one aspect, direct current having a current density of from
about 50 mA/cm.sup.2 to about 600 mA/cm.sup.2, such as from about
100 mA/cm.sup.2 to about 500 mA/cm.sup.2, such as from about 100
mA/cm.sup.2 to about 400 mA/cm.sup.2, such as from about 200
mA/cm.sup.2 to about 400 mA/cm.sup.2, for example 200 mA/cm.sup.2,
250 mA/cm.sup.2, or 300 mA/cm.sup.2 is used. The value of the
current density can be adjusted depending on the separation between
the cathode and anode. In at least one aspect, the current density
is about 50 mA/cm.sup.2, 100 mA/cm.sup.2, 150 mA/cm.sup.2, 200
mA/cm.sup.2, 250 mA/cm.sup.2, 300 mA/cm.sup.2, 350 mA/cm.sup.2, 400
mA/cm.sup.2, 450 mA/cm.sup.2, or 500 mA/cm.sup.2, where any value
can form an upper end point or a lower end point, as appropriate,
depending on the separation between the cathode and anode. For
example, a current density ranging from about 200 mA/cm.sup.2 to
about 400 mA/cm.sup.2 can be applied when the cathode and the anode
is separated by about 3 cm. It has been found by the inventors that
a current density in the aforementioned range minimizes the
formation of undesirable hexavalent chromium byproducts while
achieving a reasonable rate of deposition, for example, 0.5 to 1
micron/minute.
[0064] In response to passing a current between the cathode and the
anode, chromium and iron deposit onto the cathodic substrate.
Operation 250 is performed until a chromium alloy coating layer
having a desired thickness is formed on the substrate. In at least
one aspect, the chromium alloy coating layer is a chromium-iron
alloy having from about 1 wt. % iron to about 60 wt. % iron, such
as from about 1 wt. % iron to about 20 wt. % iron, such as from
about 1 wt. % iron to about 5 wt. % iron or from about 10 wt. %
iron to about 20 wt. % iron based on the total weight of the alloy.
For example, the chromium-iron alloy can have a wt. % iron of about
1 wt. %, 2 wt. %, 10 wt. %, 11 wt. %, or 12 wt. %. Furthermore, the
chromium-iron alloy has from about 80 wt. % chromium to about 99
wt. % chromium, such as from about 85 wt. % chromium to about 95
wt. % chromium, for example about 99 wt. % chromium, 98 wt. %
chromium, 90 wt. % chromium, 89 wt. % chromium, or 88 wt. %
chromium, based on the total weight of the alloy.
[0065] In response to performing operation 250, chromium is
deposited on the substrate. In at least one aspect, chromium and
carbon are co-deposited on the substrate. In at least one aspect,
operation 250 is performed until a chromium layer (e.g., a chromium
coating) or a chromium-carbon layer (e.g., a chromium carbide
coating) having a desired thickness (e.g., a thickness greater than
about 5 microns) is formed on the substrate. In at least one
aspect, the chromium layer having a thickness greater than about 5
microns can have hardness greater than about 800 HV.
[0066] Aspects
[0067] Clause 1. An electrolyte solution for electroplating
comprising: a trivalent chromium salt; an oxalate compound; an iron
salt; an aluminum sulfate; an alkali metal sulfate; and an alkali
metal halide.
[0068] Clause 2. The electrolyte solution of clause 1, wherein the
trivalent chromium salt is present in an amount ranging from about
0.3 mol per liter to about 0.9 mol per liter of the electrolyte
solution; the oxalate compound is present in an amount ranging from
about 0.2 mol per liter to about 1.2 mol per liter of the
electrolyte solution; the iron salt is present in an amount ranging
from about 0.005 mol per liter to about 0.2 mol per liter of the
electrolyte solution; the aluminum sulfate is present in an amount
ranging from about 0.05 mol per liter to about 0.5 mol per liter;
the alkali metal sulfate is present in an amount ranging from about
0.1 mol per liter to about 2.0 mol per liter of the electrolyte
solution; and the alkali metal halide is present in an amount
ranging from about 0.1 mol per liter to about 0.5 mol per liter of
the electrolyte solution.
[0069] Clause 3. The electrolyte solution of clause 1 or 2, wherein
the iron salt is a divalent iron salt comprising one or more of
iron (II) sulfate, iron (II) chloride, iron (II) acetate, and
hydrates thereof.
[0070] Clause 4. The electrolyte solution of any of clauses 1 to 3,
wherein the iron salt is a trivalent iron salt comprising one or
more of iron (III) sulfate, iron (III) chloride, iron (III)
acetate, and hydrates thereof.
[0071] Clause 5. The electrolyte solution of any of clauses 1 to 4,
wherein the trivalent chromium salt is selected from a chromium
(III) halide, a chromium (III) sulfate, or a combination
thereof.
[0072] Clause 6. The electrolyte solution of any of clauses 1 to 5,
wherein the oxalate compound is selected from sodium oxalate,
potassium oxalate, an acid of oxalate, or a combination
thereof.
[0073] Clause 7. The electrolyte solution of any of clauses 1 to 6,
wherein the alkali metal sulfate is selected from sodium sulfate,
potassium sulfate, or a combination thereof.
[0074] Clause 8. The electrolyte solution of any of clauses 1 to 7,
wherein the alkali metal halide is selected from sodium fluoride,
potassium fluoride, or a combination thereof.
[0075] Clause 9. The electrolyte solution of any of clauses 1 to 8,
wherein the pH of the electrolyte solution is in a range from about
1 to about 4.
[0076] Clause 10. The electrolyte solution of any of clauses 1 to
9, further comprising sodium lauryl sulfate, sodium lauryl ether
sulfate, or a combination thereof.
[0077] Clause 11. An electrolyte solution for electroplating
comprising a trivalent chromium salt in an amount ranging from
about 0.3 mol per liter to about 0.9 mol per liter of the
electrolyte solution; an oxalate compound in an amount ranging from
about 0.2 mol per liter to about 1.2 mol per liter of the
electrolyte solution; an iron salt in an amount ranging from about
0.005 mol per liter to about 0.2 mol per liter of the electrolyte
solution; an aluminum sulfate in an amount ranging from about 0.05
mol per liter to about 0.5 mol per liter; an alkali metal sulfate
in an amount ranging from about 0.1 mol per liter to about 2.0 mol
per liter of the electrolyte solution; and an alkali metal halide
in an amount ranging from about 0.1 mol per liter to about 0.5 mol
per liter of the electrolyte solution.
[0078] Clause 12. The electrolyte solution of clause 11, wherein
the iron salt is a divalent iron salt comprising one or more of
iron (II) sulfate, iron (II) chloride, iron (II) acetate, and
hydrates thereof.
[0079] Clause 13. The electrolyte solution of clause 11 or 12,
wherein the iron salt is a trivalent iron salt comprising one or
more of iron (III) sulfate, iron (III) chloride, iron (III)
acetate, and hydrates thereof.
[0080] Clause 14. The electrolyte solution of any of clauses 11 to
13, wherein the trivalent chromium salt is selected from a chromium
(III) halide, a chromium (III) sulfate, or a combination
thereof.
[0081] Clause 15. The electrolyte solution of any of clauses 11 to
14, wherein the oxalate compound is selected from sodium oxalate,
potassium oxalate, an acid of oxalate, or a combination
thereof.
[0082] Clause 16. The electrolyte solution of any of clauses 11 to
15, wherein the alkali metal sulfate is selected from sodium
sulfate, potassium sulfate, or a combination thereof.
[0083] Clause 17. The electrolyte solution of any of clauses 11 to
16, wherein the alkali metal halide is selected from sodium
fluoride, potassium fluoride, or a combination thereof.
[0084] Clause 18. The electrolyte solution of any of clauses 11 to
17, wherein the pH of the electrolyte solution is in a range from
about 1 to about 4.
[0085] Clause 19. The electrolyte solution of any of clauses 11 to
18, further comprising sodium lauryl sulfate, sodium lauryl ether
sulfate, or a combination thereof.
[0086] Clause 20. A method of chrome plating on a substrate using
an electrolyte solution, comprising dissolving in an aqueous medium
a trivalent chromium salt in an amount ranging from about 0.3 mol
per liter to about 0.9 mol per liter of the electrolyte solution;
dissolving a oxalate compound in an amount ranging from about 0.2
mol per liter to about 1.2 mol per liter of the electrolyte
solution; dissolving iron salt in an amount ranging from about
0.005 mol per liter to about 0.2 mol per liter of the electrolyte
solution; dissolving aluminum sulfate in an amount ranging from
about 0.05 mol per liter to about 0.5 mol per liter; dissolving an
alkali metal sulfate in an amount ranging from about 0.1 mol per
liter to about 2.0 mol per liter of the electrolyte solution;
dissolving an alkali metal halide in an amount ranging from about
0.1 mol per liter to about 0.5 mol per liter of the electrolyte
solution; and passing a current between a cathode and an anode
through the electrolyte solution to deposit chromium on a
substrate.
[0087] Clause 21. The method of clause 20, wherein the cathode is a
steel substrate, a copper substrate, a brass substrate, a nickel
substrate, a copper-coated substrate, or a nickel-coated
substrate.
[0088] Clause 22. The method of clause 20 or 21, wherein the anode
is a platinum material, platinized titanium material, or a
carbonaceous electrode material.
[0089] Clause 23. The method of any of clauses 20 to 22, wherein
the current has a current density in a range from about 150 to
about 600 mA/cm.sup.2 by passing direct current between the anode
and the cathode.
[0090] Clause 24. The method of any of clauses 20 to 23, wherein
the current density has a current density in a range from about 200
to about 400 mA/cm.sup.2.
[0091] Clause 25. The method of any of clauses 20 to 24, wherein
the electrolyte solution is maintained at a temperature in a range
from about 20 degrees Celsius and about 60 degrees Celsius.
[0092] Clause 26. The method of any of clauses 20 to 25, further
comprising adjusting a pH of the electrolyte solution to a pH in a
range from about 1.5 to about 4.
[0093] Clause 27. The method of any of clauses 20 to 26, wherein
the iron salt is a divalent iron salt comprising one or more of
iron (II) sulfate, iron (II) chloride, iron (II) acetate, and
hydrates thereof.
[0094] Clause 28. The method of any of clauses 20 to 27, wherein
the iron salt is a trivalent iron salt comprising one or more of
iron (III) sulfate, iron (III) chloride, iron (III) acetate, and
hydrates thereof.
[0095] Clause 29. The method of any of clauses 20 to 28, wherein
the trivalent chromium salt is selected from a chromium (III)
halide, a chromium (III) sulfate, or a combination thereof.
[0096] Clause 30. The method of any of clauses 20 to 29, wherein
the oxalate compound is selected from sodium oxalate, potassium
oxalate, an acid of oxalate, or a combination thereof.
[0097] Clause 31. The method of any of clauses 20 to 30, wherein
the alkali metal sulfate is selected from sodium sulfate, potassium
sulfate, or a combination thereof.
[0098] Clause 32. The method of any of clauses 20 to 31, wherein
the alkali metal halide is selected from sodium fluoride, potassium
fluoride, or a combination thereof.
[0099] Clause 33. The method of any of clauses 20 to 32, further
comprising dissolving sodium lauryl sulfate, sodium lauryl ether
sulfate, or a combination thereof in an amount ranging from about
0.1 grams per liter to about 1 gram per liter of the electrolyte
solution.
[0100] Clause 34. A method of chrome plating on a substrate using
an electrolyte solution, comprising: introducing a cathode and an
anode into an electrolyte solution comprising a trivalent chromium
salt, an oxalate compound, an iron salt, an aluminum sulfate, an
alkali metal sulfate, and an alkali metal halide; and passing a
current between the anode and the cathode through the electrolyte
to deposit a chromium layer on the substrate.
[0101] Clause 35. The method of clause 34, wherein the cathode is a
steel substrate, a copper substrate, a brass substrate, a nickel
substrate, a copper-coated substrate, or a nickel-coated
substrate.
[0102] Clause 36. The method of clause 34 or 35, wherein the anode
is a platinum material, platinized titanium material, or a
carbonaceous electrode material.
[0103] Clause 37. The method of any of clauses 34 to 36, wherein
the current has a current density in a range from about 100 to
about 600 mA/cm.sup.2 by passing direct current between the anode
and the cathode.
[0104] Clause 38. The method of any of clauses 34 to 37, wherein
the current density has a current density in a range from about 200
to about 400 mA/cm.sup.2.
[0105] Clause 39. The method of any of clauses 34 to 38, wherein
the electrolyte solution is maintained at a temperature in a range
from about 20 degrees Celsius and about 60 degrees Celsius.
[0106] Clause 40. The method of any of clauses 34 to 39, further
comprising adjusting a pH of the electrolyte solution to a pH in a
range from about 1.5 to about 4.
[0107] Clause 41. The method of any of clauses 34 to 40, wherein
the iron salt is a divalent iron salt comprising one or more of
iron (II) sulfate, iron (II) chloride, iron (II) acetate, and
hydrates thereof.
[0108] Clause 42. The method of any of clauses 34 to 41, wherein
the iron salt is a trivalent iron salt comprising one or more of
iron (III) sulfate, iron (III) chloride, iron (III) acetate, and
hydrates thereof.
[0109] Clause 43. The method of any of clauses 34 to 42, wherein
the trivalent chromium salt is selected from a chromium (III)
halide, a chromium (III) sulfate, or a combination thereof.
[0110] Clause 44. The method of any of clauses 34 to 43, wherein
the oxalate compound is selected from sodium oxalate, potassium
oxalate, an acid of oxalate, or a combination thereof.
[0111] Clause 45. The method of any of clauses 34 to 44, wherein
the alkali metal sulfate is selected from sodium sulfate, potassium
sulfate, or a combination thereof.
[0112] Clause 46. The method of any of clauses 34 to 45, wherein
the alkali metal halide is selected from sodium fluoride, potassium
fluoride, or a combination thereof.
[0113] Clause 47. The method of any of clauses 34 to 46, further
comprising dissolving sodium lauryl sulfate, sodium lauryl ether
sulfate, or a combination thereof in an amount ranging from about
0.1 grams per liter to about 1 gram per liter of the electrolyte
solution.
[0114] Clause 48. A substrate comprising: a chromium-iron alloy
coating having a chromium content in a range of about 40 wt. % to
about 90 wt. %, an iron content in a range of about 8 wt. % to
about 18 wt. %, and a carbon content in the range of about 5 wt. %
to about 50 wt. %.
[0115] Clause 49. The substrate of clause 48, wherein the substrate
comprises one or more of steel, copper, brass, or nickel.
[0116] Clause 50. The substrate of clause 48 or 49, wherein the
coating has a thickness of from about 1 micron and about 100
microns.
EXAMPLES
[0117] The following non-limiting examples are provided to further
illustrate aspects described herein. However, the examples are not
intended to be all-inclusive and are not intended to limit the
scope of the aspects described herein.
[0118] Example 1
[0119] The components of Example 1 were mixed in a stepwise manner
with the chromium chloride hexahydrate and the sodium oxalate mixed
first followed by the metal salts. The pH of Example 1 was
.about.2.2.
TABLE-US-00001 Chromium chloride hexahydrate 159 g/L 0.6 M
(CrCl.sub.3.cndot.6H.sub.2O) Sodium oxalate 80.4 g/L 0.6 M
(Na.sub.2C.sub.2O.sub.4) Ferrous sulfate hetpahydrate 2.78 g/L 0.01
M (FeSO.sub.4.cndot.7H.sub.2O) Aluminum sulfate
(Al.sub.2(SO.sub.4).sub.3) 126.1 g/L 0.2 M Sodium sulfate
(Na.sub.2SO.sub.4) 184.6 g/L 1.3 M Sodium fluoride (NaF) 16.8 g/L
0.4 M
[0120] Example 2
[0121] The components of Example 2 were mixed in a stepwise manner
with the chromium chloride hexahydrate and the sodium oxalate mixed
first followed by the metal salts. The components of Example 2 are
similar to the components of Example 1, except that the amount of
ferrous sulfate heptahydrate was increased 10 times compared to the
components of Example 1. The pH of Example 1 was .about.2.2.
TABLE-US-00002 Chromium chloride hexahydrate 159 g/L 0.6 M
(CrCl.sub.3.cndot.6H.sub.2O) Sodium oxalate 80.4 g/L 0.6 M
(Na.sub.2C.sub.2O.sub.4) Ferrous sulfate hetpahydrate 27.8 g/L 0.1
M (FeSO.sub.4.cndot.7H.sub.2O) Aluminum sulfate
(Al.sub.2(SO.sub.4).sub.3) 126.1 g/L 0.2 M Sodium sulfate
(Na.sub.2SO.sub.4) 184.6 g/L 1.3 M Sodium fluoride (NaF) 16.8 g/L
0.4 M
[0122] Example 3
[0123] The components of Example 3 were mixed in a stepwise manner
with the chromium chloride hexahydrate and the sodium oxalate mixed
first followed by the metal salts. The components of Example 3 are
similar to the components of Example 1, except that ferrous sulfate
heptahydrate is replaced with ferric chloride in Example 3. The pH
of Example 1 was approximately 2.2.
TABLE-US-00003 Chromium chloride hexahydrate 159 g/L 0.6 M
(CrCl.sub.3.cndot.6H.sub.2O) Sodium oxalate 80.4 g/L 0.6 M
(Na.sub.2C.sub.2O.sub.4) Ferric chloride 1.62 g/L 0.01 M
(FeCl.sub.3) Aluminum sulfate (Al.sub.2(SO.sub.4).sub.3) 126.1 g/L
0.2 M Sodium sulfate (Na.sub.2SO.sub.4) 184.6 g/L 1.3 M Sodium
fluoride (NaF) 16.8 g/L 0.4 M
[0124] FIG. 3 is an image 300 of chromium-iron alloy plated
substrates 310, 320, 330, and 340, formed by the process of FIG. 2,
each plated at a different current density using the electrolyte
solution of Example 1. For each chromium-iron alloy plated
substrate 310, 320, 330, and 340, the plating parameters were a
plating time of approximately 1 hour while maintaining the
electrolyte solution at a temperature of 30.degree. C. and a pH of
approximately 2.2. Chromium-iron alloy plated substrate 310 was
plated at a current density of 100 mA/cm.sup.2 resulting in a
chromium-iron alloy layer having a thickness of 12 .mu.m.
Chromium-iron alloy plated substrate 320 was plated at a current
density of 200 mA/cm.sup.2 resulting in a chromium-iron alloy layer
having a thickness of 15 .mu.m. Chromium-iron alloy plated
substrate 330 was plated at a current density of 250 mA/cm.sup.2
resulting in a chromium-iron alloy layer having a thickness of 28
.mu.m. Chromium-iron alloy plated substrate 340 was plated at a
current density of 300 mA/cm.sup.2 resulting in a chromium-iron
layer having a thickness of 32 .mu.m. X-ray fluorescence was
performed on a portion of each coating to determine the chromium
content and the iron content by wt. %. It is noted that X-ray
fluorescence does not detect carbon, thus in at least one aspect,
the chromium-iron alloys described herein also contain carbon even
though carbon is not shown in the X-ray fluorescence results. The
results are depicted in Table I.
[0125] As illustrated in Table I, any current density ranging from
100 mA/cm.sup.2 to about 300 mA/cm.sup.2 provides deposition of a
chromium-iron alloy layer. A current density ranging from about 200
mA/cm.sup.2 to about 280 mA/cm.sup.2 provides a thick chromium-iron
alloy layer with a low iron content. Further, a current density of
100 mA/cm.sup.2 provides the thinnest chromium-iron alloy with a
high iron content relative to a current density ranging from about
200 mA/cm.sup.2 to about 300 mA/cm.sup.2.
TABLE-US-00004 TABLE I Current Density Chromium Iron Thickness
(mA/cm.sup.2) (wt. %) (wt. %) (.mu.m) 100 10.2 89.8 12 200 82.4
17.6 15 250 92.7 7.3 28 300 94.3 5.7 32
[0126] FIG. 4 is an image 400 of chromium-iron alloy plated
substrates 410, 420, 430, 440, and 450 formed by the process of
FIG. 2, each plated at a different pH using the electrolyte
solution of Example 1. For each chromium-iron alloy plated
substrate 410, 420, 430, 440, and 450, the plating parameters were
a direct current at a current density of 250 mA/cm.sup.2 at a
plating time of approximately 1 hour while maintaining the
electrolyte solution at a temperature of 30.degree. C.
Chromium-iron alloy plated substrate 410 was plated at a pH of 1.0
resulting in patchy chromium-iron alloy deposits, which were not
measured but were believed to be less than 10 .mu.m. Chromium-iron
alloy plated substrate 420 was plated at a pH of 2.0 resulting in
patchy chromium-iron alloy deposits, which were not measured, but
were believed to be less than 10 .mu.m. Chromium-iron alloy plated
substrate 430 was plated at a pH of 2.5 resulting in a
chromium-iron alloy layer having a thickness of 20 .mu.m.
Chromium-iron alloy plated substrate 440 was plated at a pH of 3.0
resulting in a chromium-iron alloy layer having a thickness of 28
.mu.m. Chromium-iron alloy plated substrate 450 was plated at a pH
of 3.5 resulting in a chromium-iron alloy layer having a thickness
of 45 .mu.m. X-ray fluorescence was performed on a portion of each
coating to determine the chromium content and the iron content by
wt. %. The results are depicted in Table II.
[0127] As illustrated in Table II, any pH ranging from 2.5 to 3.5
provides deposition of a chromium-iron alloy layer. A pH range of
2.5 to 3.0 advantageously provides a thick chromium-iron alloy
layer having a desired iron content. A pH of 3.5 provides a thicker
chromium-iron alloy layer with a lower iron content relative to a
pH range of 2.5 to 3.0.
TABLE-US-00005 TABLE II Chromium Iron Thickness pH (wt. %) (wt. %)
(.mu.m) 1.5 2.7 97.3 <10 2.0 27.6 72.4 <10 2.5 74.1 25.9 20
3.0 85.9 14.1 28 3.5 90.3 9.7 45
[0128] FIG. 5 is an image 500 of chromium-iron alloy plated
substrates 510, 520, 530, and 540 formed by the process of FIG. 2,
each plated at a different current density using the electrolyte
solution of Example 2. For each chromium-iron alloy plated
substrate 510, 520, 530, and 540, the plating parameters were a
plating time of approximately 1 hour while maintaining the
electrolyte solution at a temperature of 30.degree. C. and a pH of
approximately 2.2. Chromium-iron alloy plated substrate 510 was
plated at a current density of 100 mA/cm.sup.2 resulting in a
chromium-iron alloy layer having a thickness of 30 .mu.m.
Chromium-iron alloy plated substrate 520 was plated at a current
density of 200 mA/cm.sup.2 resulting in a chromium-iron alloy layer
having a thickness of 40 .mu.m. Chromium-iron alloy plated
substrate 530 was plated at a current density of 250 mA/cm.sup.2
resulting in a chromium-iron alloy layer having a thickness of 70
.mu.m. Chromium-iron alloy plated substrate 540 was plated at a
current density of 300 mA/cm.sup.2 resulting in a chromium-iron
layer having a thickness of 50 .mu.m. X-ray fluorescence was
performed on a portion of each coating to determine the chromium
content and the iron content by wt. %. The results are depicted in
Table III.
[0129] As illustrated in Table III, any current density ranging
from 100 mA/cm.sup.2 to about 300 mA/cm.sup.2 provides deposition
of a chromium-iron alloy. A current density ranging from about 100
mA/cm.sup.2 to about 250 mA/cm.sup.2 provides a thick chromium-iron
alloy layer. Further, at a current density of 300 mA/cm.sup.2 the
thickness of the chromium-iron alloy decreases relative to the
thickness of the chromium-iron alloy deposited at a current density
of 250 mA/cm.sup.2.
TABLE-US-00006 TABLE III Current Density Chromium Iron Thickness
(mA/cm.sup.2) (wt. %) (wt. %) (.mu.m) 100 27.6 72.4 30 200 52.5
47.5 40 250 60.5 39.5 70 300 59.2 40.8 50
[0130] FIG. 6 is an image 600 of chromium-iron alloy plated
substrates 610, 620, 630, 640, 650, and 660 formed by the process
of FIG. 2, each plated at a different pH using the electrolyte
solution of Example 2. For each chromium-iron alloy plated
substrate 610, 620, 630, 640, 650, and 660, the plating parameters
were a direct current at a current density of 250 mA/cm.sup.2 at a
plating time of approximately 1 hour while maintaining the
electrolyte solution at a temperature of 30.degree. C.
Chromium-iron alloy plated substrate 610 was plated at a pH of 1.5
resulting in patchy chromium-iron alloy deposit. Chromium-iron
alloy plated substrate 620 was plated at a pH of 2.0 resulting in
patchy chromium-iron alloy deposits. Chromium-iron alloy plated
substrate 630 was plated at a pH of 2.5 resulting in a
chromium-iron alloy layer having a thickness of 50 .mu.m.
Chromium-iron alloy plated substrate 640 was plated at a pH of 3.0
resulting in a chromium-iron alloy layer having a thickness of 70
.mu.m. Chromium-iron alloy plated substrate 650 was plated at a pH
of 3.5 resulting in a chromium-iron alloy layer having a thickness
of 50 .mu.m. Chromium-iron alloy plated substrate 660 was plated at
a pH of 4.0. X-ray fluorescence was performed on a portion of each
coating to determine the chromium content and the iron content by
wt. %. The results are depicted in Table IV.
[0131] As illustrated in Table IV, any pH ranging from 1.5 to 4.0
provides deposition of a chromium-iron alloy layer. A pH range of
2.0 to 4.0 advantageously provides a thick chromium-iron alloy
layer having a desired high chromium content. A pH of 3.0 provides
a thicker chromium-iron alloy layer with good quality deposits. At
a pH of 4, the deposits exhibited burning at the edges, while at a
pH of 2 or lower, the deposits were patchy.
TABLE-US-00007 TABLE IV Chromium Iron Thickness pH (wt. %) (wt. %)
(.mu.m) 1.5 20.9 79.1 Patchy deposit 2.0 34.8 65.2 Patchy deposit
2.5 38.4 61.6 50 3.0 43.8 56.8 70 3.5 49.0 51.0 50 4.0 50.6 49.4
Burning at edges
[0132] FIG. 7 is an image 700 of chromium-iron alloy plated
substrates 710, 720, 730, 740, 750, and 760 formed by the process
of FIG. 2, each plated at a different current density using the
electrolyte solution of Example 3. For each chromium-iron alloy
plated substrate 710, 720, 730, 740, 750, and 760, the plating
parameters were a plating time of approximately 1 hour while
maintaining the electrolyte solution at a temperature of 30.degree.
C. and a pH of approximately 2.2. Chromium-iron alloy plated
substrate 710 was plated at a current density of 100 mA/cm.sup.2
resulting in patchy chromium-iron alloy deposits believed to be
less than 10 .mu.m thick. Chromium-iron alloy plated substrate 720
was plated at a current density of 150 mA/cm.sup.2 resulting in
patchy chromium-iron alloy deposits believed to be less than 10
.mu.m thick. Chromium-iron alloy plated substrate 730 was plated at
a current density of 200 mA/cm.sup.2 resulting in a chromium-iron
alloy layer having a thickness of 10 .mu.m. Chromium-iron alloy
plated substrate 740 was plated at a current density of 300
mA/cm.sup.2 resulting in a chromium-iron layer having a thickness
of 30 .mu.m. Chromium-iron alloy plated substrate 750 was plated at
a current density of 400 mA/cm.sup.2 resulting in a chromium-iron
layer having a thickness of 50 .mu.m. Chromium-iron alloy plated
substrate 760 was plated at a current density of 500 mA/cm.sup.2
resulting in deposits, which exhibited burning at the edges.
[0133] As illustrated in Table V, any current density ranging from
200 mA/cm.sup.2 to about 400 mA/cm.sup.2 provides deposition of a
chromium-iron alloy. A current density ranging from about 300
mA/cm.sup.2 to about 400 mA/cm.sup.2 provides a thick chromium-iron
alloy layer. Further at a current density of 500 mA/cm.sup.2 the
thickness of the chromium-iron alloy increased relative to the
thickness of the chromium-iron alloy deposited at a current density
of 400 mA/cm.sup.2, but the deposits at the edges were burned
(black powder).
TABLE-US-00008 TABLE V Current Density Thickness (mA/cm.sup.2)
(.mu.m) 100 (<10) patchy deposit 150 (<10) patchy deposit 200
10 300 30 400 50 500 (100) burning at edges
[0134] FIG. 8 is an image 800 of chromium-iron alloy plated
substrates 810, 820, 830, 840, 850, 860, and 870 formed by the
process of FIG. 2, each plated at a different pH using the
electrolyte solution of Example 3. For each chromium-iron alloy
plated substrate 810, 820, 830, 840, 850, 860, and 870, the plating
parameters were a direct current at a current density of 250
mA/cm.sup.2 at a plating time of approximately 1 hour while
maintaining the electrolyte solution at a temperature of
approximately 30.degree. C. Chromium-iron alloy plated substrate
810 was plated at a pH of 1.0 resulting in a chromium-iron alloy
layer having a thickness of 20 .mu.m. Chromium-iron alloy plated
substrate 820 was plated at a pH of 1.5 resulting in a
chromium-iron alloy layer having a thickness of 24 .mu.m.
Chromium-iron alloy plated substrate 830 was plated at a pH of 2.0
resulting in a chromium-iron alloy layer having a thickness of 20
.mu.m. Chromium-iron alloy plated substrate 840 was plated at a pH
of 3.0 resulting in a chromium-iron alloy layer having a thickness
of 16 .mu.m. Chromium-iron alloy plated substrate 860 was plated at
a pH of 3.5 resulting in a chromium-iron alloy layer having a
thickness of 16 .mu.m. Chromium-iron alloy plated substrate 870 was
plated at a pH of 4.0 resulting in patchy chromium-iron alloy
deposits of low thickness. X-ray fluorescence was performed on a
portion of coatings deposited at a pH of 2 and a pH of 2.5 to
determine the chromium content and the iron content by wt. %. The
results are depicted in Table VI.
[0135] As illustrated in Table VI, any pH ranging from 1.0 to 4.0
provides deposition of a chromium-iron alloy. A pH ranging from 1.0
to 2.5 advantageously provides a thicker chromium-iron alloy layer
than a pH that is higher. Further, a pH ranging from 1.5 to 2.0
provides the thickest chromium-iron alloy layer.
TABLE-US-00009 TABLE VI Chromium Iron Thickness pH (wt. %) (wt. %)
(.mu.m) 1.0 20 1.5 24 2.0 45 55 24 2.5 46 54 20 3.0 16 3.5 16 4.0
patchy deposits
[0136] FIG. 9 is an image 900 of chromium-iron alloy plated
substrates 910, 920, 930, and 940 formed by the process of FIG. 2,
each plated at a different temperature using the electrolyte
solution of Example 3. For each chromium-iron alloy plated
substrate 910, 920, 930, and 940, the plating parameters were a
direct current at a current density of 250 mA/cm.sup.2 at a plating
time of approximately 1 hour while maintaining the electrolyte
solution at a pH of approximately 2.1. Chromium-iron alloy plated
substrate 910 was plated at a temperature of 30 .degree. C.
resulting in a chromium-iron alloy layer having a thickness of 40
.mu.m. Chromium-iron alloy plated substrate 920 was plated at a
temperature of 40.degree. C. resulting in a chromium-iron alloy
layer having a thickness of 30 .mu.m. Chromium-iron alloy plated
substrate 930 was plated at a temperature of 50.degree. C.
resulting in a chromium-iron alloy layer having a thickness of 30
.mu.m. Chromium-iron alloy plated substrate 940 was plated at a
temperature of 60.degree. C. resulting in a chromium-iron alloy
layer having a low thickness. The results are depicted in Table
VII.
[0137] As illustrated by Table VII, any temperature ranging from
about 30.degree. C. to about 50.degree. C. provides deposition of a
chromium-iron alloy layer. The operating temperature of 30.degree.
C. provides the thickest chromium-iron alloy layer, but the
deposits at 40.degree. C. were aesthetically better.
TABLE-US-00010 TABLE VII Temperature Chromium Iron Thickness
(.degree. C.) (wt. %) (wt. %) (.mu.m) 30 40 60 40 40 41 59 30 50 43
57 30 60 45 55 14
[0138] Using the electrolyte solution of Example 3,
chromium-iron-alloy coatings were deposited on a Taber Wear panels
by a direct current at a current density of 300 mA/cm.sup.2 for a
plating time of approximately 2 hours while maintaining the
electrolyte solution at a temperature of approximately 40.degree.
C. and a pH of approximately 2.5. The alloy composition of the
coating as measured by SEM-EDS was chromium at .about.41 wt. %,
iron at .about.10 wt. %, and carbon at .about.49 wt. %. Hardness
values were measured on `as plated` coupons as well as after baking
the coupons at approximately 190.degree. C. for 23 hours. The
obtained chromium-iron-alloy coatings were evaluated as to wear
resistance. Measurement of wear resistance was performed using a
Taber wear test specified according to ASTM D 4060. The abrasive
wheels used were CS10, with a load of 500 g per wheel, abrasion was
performed for 10,000 cycles, at a rotary speed of 60 rpm. The Taber
wear index was less than 10. The average of 5 hardness measurements
for the "as plated" chromium-iron alloy layer was 1056 HV. The
average of 5 hardness measurements for the `baked` chromium-iron
alloy layer was 1187 HV.
[0139] Using the electrolyte solution of Example 1,
chromium-iron-alloy coatings were deposited on steel substrates by
a direct current at a current density of 250 mA/cm.sup.2 for a
plating time of approximately 2 hours while maintaining the
electrolyte solution at a temperature of approximately 35.degree.
C. and a pH of approximately 2.5. The alloy composition of the
coating as measure by SEM-EDS was chromium at .about.80 wt. %, iron
at .about.12 wt. %, and carbon at .about.8 wt. %. Hardness values
were measured on `as plated` coupons as well as after baking the
coupons at approximately 190.degree. C. for 23 hours. The average
of 5 hardness measurements for the "as plated" chromium-iron alloy
layer was 1147 HV. The average of 5 hardness measurements for the
`baked` chromium-iron alloy layer was 1249 HV.
[0140] Overall, the present disclosure provides improved
electrolyte solutions for electrodeposition of chromium-iron
alloys, methods of forming chromium-iron alloys, and methods of
electrodepositing chromium-iron alloys.
[0141] The descriptions of the various aspects of the present
disclosure have been presented for purposes of illustration, but
are not intended to be exhaustive or limited to the aspects
disclosed. Many modifications and variations will be apparent to
those of ordinary skill in the art without departing from the scope
and spirit of the described aspects. The terminology used herein
was chosen to best explain the principles of the aspects, the
practical application or technical improvement over technologies
found in the marketplace, or to enable others of ordinary skill in
the art to understand the aspects disclosed herein. While the
foregoing is directed to aspects of the present disclosure, other
and further aspects of the present disclosure can be devised
without departing from the basic scope thereof.
* * * * *