U.S. patent application number 10/380212 was filed with the patent office on 2004-05-13 for ternary tin zinc alloy, electroplating solutions and galvanic method for producing ternary tin zinc alloy coatings.
Invention is credited to Dumke, Steffen, Leyendecker, Klaus, Reissmuller, Klaus, nter Wirth, G?uuml.
Application Number | 20040091385 10/380212 |
Document ID | / |
Family ID | 7656548 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040091385 |
Kind Code |
A1 |
Leyendecker, Klaus ; et
al. |
May 13, 2004 |
Ternary tin zinc alloy, electroplating solutions and galvanic
method for producing ternary tin zinc alloy coatings
Abstract
The invention relates to ternary tin zinc alloy coatings 30-65
wt. % tin, 30-65 wt. % zinc and 0.1-15 wt. % metal from the
following group as a third alloy component; iron, cobalt, nickel.
Correspondingly, alloy coatings can be produced by means of
electrolytic deposition from aqueous galvanic electroplating
solutions which contain the components of the alloy in a dissolved
form. The alloy coatings are characterised in that they have a
particularly high resistance to corrosion and are particularly
suitable as anti-corrosion protective coatings on iron-based
materials.
Inventors: |
Leyendecker, Klaus;
(Durlangen, DE) ; Wirth, G?uuml;nter;
(B?ouml;bingen, DE) ; Reissmuller, Klaus;
(Spraitbach, DE) ; Dumke, Steffen;
(D?uuml;bendorf, CH) |
Correspondence
Address: |
KALOW & SPRINGUT LLP
488 MADISON AVENUE
19TH FLOOR
NEW YORK
NY
10022
US
|
Family ID: |
7656548 |
Appl. No.: |
10/380212 |
Filed: |
December 18, 2003 |
PCT Filed: |
August 16, 2001 |
PCT NO: |
PCT/EP01/09452 |
Current U.S.
Class: |
420/524 ;
420/557; 420/589 |
Current CPC
Class: |
C22C 13/00 20130101;
C25D 3/565 20130101; C22C 18/00 20130101; C25D 3/60 20130101 |
Class at
Publication: |
420/524 ;
420/557; 420/589 |
International
Class: |
C22C 013/00; C22C
018/00; C22C 030/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 2000 |
DE |
100 45 991.9 |
Claims
1. Ternary tin-zinc alloys characterized in that they consist of 30
to 65% by weight tin, 30 to 65% by weight zinc, and 0.1 to 15% by
weight of a metal from the group iron, cobalt, or nickel as the
third alloy component.
2. Ternary tin-zinc alloys according to claim 1, characterized in
that they consist of 40 to 55% by weight tin, 45 to 55% by weight
zinc and 1 to 5% by weight cobalt.
3. Ternary tin-zinc alloys according to claim 1, characterized in
that they consist of 35 to 50% by weight tin, 50 to 65% by weight
zinc and 0.1 to 5% by weight nickel.
4. Ternary tin-zinc alloys according to claim 1, characterized in
that they consist of 40 to 55% by weight tin, 40 to 60% by weight
zinc and 1 to 8% by weight iron.
5. Alkaline, neutral or weakly acidic galvanic electrolyte baths
containing the alloy components in dissolved form and, optionally,
other usual additives, for electrolytic production of alloy layers
of ternary tin-zinc alloys according to claims 1 to 4.
6. Process for producing alloy layers of ternary tin-zinc alloys
according to claims 1 to 4, characterized in that they are
deposited electrolytically from an alkaline, neutral or weakly
acidic galvanic electrolyte bath containing the alloy components in
dissolved form with, optionally, other usual additives.
7. Use of galvanically produced alloy layers of ternary tin-zinc
alloys according to claims 1 to 4 as anticorrosion layers.
8. Use of galvanically produced alloy layers of ternary tin-zinc
alloys according to claims 1 to 4, with subsequent passivation, as
anticorrosion layers on ferrous materials.
9. Use of galvanically produced alloy layers of ternary tin-zinc
alloys according to claims 1 to 4 as weldable coatings.
10. Use of galvanically produced alloy layers of ternary tin-zinc
alloys according to claims 1 to 4 as final decorative coatings.
Description
[0001] The invention concerns new ternary tin-zinc alloys of
specific compositions which contain a metal from the group iron,
cobalt, or nickel as a third alloy component. The invention further
concerns electrolytic baths and a galvanic process for producing
such ternary tin-zinc alloys, as well as their use as
corrosion-protection layers or decorative layers.
[0002] It is well known that ferrous materials can be protected
against corrosion by coating with zinc and subsequent passivation,
such as by chromating (based on Cr.sup.+6) or chromiting (based on
Cr.sup.+3), evident by a yellow, blue, black, or olive-green
coloration of the surface. These measures can be used to attain
protection times of 200 to 600 hours to the first appearance of red
rust in salt mist testing (DIN 50021-SS) (Corrosion protection by
protective layers and coatings, D. Grimme and J. Kruuger, Weka
Fachverlag fuur technische Fuhrungskrafte, Augsburg).
[0003] More stringent requirements, such as resistance of up to
1000 hours until the first appearance of red rust in the salt mist
test, can be met by coating with zinc alloys which contain nickel,
cobalt or iron as components of the alloy and subsequent
chromating. The proportions of the alloying elements can, for
instance, be from less than 1% by weight, such as 0.4-0.6% by
weight Fe in the ZnFe system up to 15% by weight, such as 12-15% by
weight Ni in the ZnNi system (Zinc alloying processes: Properties
and applications in technology, Dr. A. Jimenez, B. Kerle and H.
Schmidt, Galvanotechnik 89 (1998)4).
[0004] Tin-zinc alloys can also be used as anticorrosion coatings
for iron. Values of up to 1000 hours until the first appearance of
red rust in salt mist testing are attained with chromated SnZn
coatings. The most favorable alloy composition is 70% by weight Sn
and 30% by weight Zn. The low hardness, only about 50 HV, of SnZn
coatings is considered a disadvantage (Tin-Zinc Plating, E. Budmann
and D. Stevens, Trans. IMF 76 (1998)3).
[0005] Observation of developments in the field of corrosion
protection of ferrous materials, as in the automobile industry,
indicates that there will be higher requirements for anticorrosion
systems in the future, which cannot be met with known processes.
Such increased requirements are on the order of 3000 hours
resistance in salt mist tests. Furthermore, such anticorrosion
coatings should have the highest possible hardness, be resistant to
wear, and should also, as much as possible, be weldable.
[0006] The invention was, therefore, based on the objective of
finding new alloy systems with particularly high corrosion
resistance, and providing galvanic electrolytes for deposition of
these alloys, to meet future requirements for anticorrosion
effect.
[0007] Now it has been found that ternary tin-zinc alloys
containing from 30 to 65% by weight tin, 30 to 65% by weight zinc,
and 0.1 to 15% by weight of a metal from the group iron, cobalt, or
nickel as the third alloy component meet these requirements
superbly well.
[0008] The subject of the invention is, then, ternary tin-zinc
alloys characterized in that they consist of 30 to 65% by weight
tin, 30 to 65% by weight zinc, and 0.1 to 15% by weight of a metal
from the group iron, cobalt, or nickel as the third alloy
component.
[0009] The ternary tin-zinc alloys according to the invention
preferably contain cobalt as the third alloying component.
[0010] Tin-zinc-cobalt alloys according to the invention preferably
contain 40 to 55% by weight tin, 45 to 55% by weight zinc and 0.1
to 5% by weight cobalt. Tin-zinc-nickel alloys according to the
invention preferably contain 35 to 50% by weight tin, 50 to 65% by
weight zinc and 0.1 to 5% by weight nickel. Tin-zinc-iron alloys
according to the invention preferably contain 40 to 55% by weight
tin, 40 to 60% by weight zinc and 1 to 8% by weight iron.
[0011] The ternary tin-zinc alloys according to the invention can
be produced from the individual components by fusion or powder
metallurgy.
[0012] Electrolytic preparation is preferable, particularly with
respect to typical applications. That is done by electrolytic
deposition from aqueous galvanic electrolyte baths which contain
the alloy components in dissolved form. The ternary tin-zinc alloys
can be deposited onto substrates from alkaline, neutral, or weakly
acidic electrolytic baths. Here an alkaline electrolyte is
understood to be an electrolyte with a pH greater than 10. A
neutral electrolyte is considered to be one with a pH from 6 to 10.
A weakly acidic electrolyte is considered to be one with a pH of
3-6.
[0013] The alloy components are added to the aqueous electrolyte
bath in the form of their compounds which are soluble and ionogenic
in the particular medium. Tin is preferably added as the sulfate,
chloride, sulfonate, or oxalate, or as sodium or potassium
stannate. Zinc is preferably added as the sulfate, chloride,
hydroxide, sulfonate or oxide. The element, iron, cobalt, or
nickel, which acts as the third alloy component, is preferably
added as the sulfate, chloride, hydroxide or carbonate.
[0014] The galvanic electrolyte according to the invention for
producing ternary tin-zinc alloy coatings can also contain other
additives common and well-known in plating technology. Those can be
bases for pH adjustment, such as sodium, potassium, or ammonium
hydroxide, or inorganic acids, such as hydrochloric acid, sulfuric
acid, phosphoric acid, or boric acid; alkali salts of these acids
as buffers and/or conductive salts; organic acids such as
hydroxycarboxylic acids and/or their salts, such as citric acid;
complexing agents such as EDTA, wetting agents, brighteners, etc. A
person skilled in the art will be familiar with the criteria for
qualitative and quantitative selection of such additives and their
functions in galvanic baths.
[0015] The proportions of the metals in the electrodeposited alloy
coating can be influenced, in the known manner, by the proportion
of metals in the bath composition, by the nature and proportion of
the other bath components, and by the deposition parameters.
[0016] For electrolytic deposition of the ternary tin-zinc alloys
according to the invention, the substrate to be coated, such as a
part made from a ferrous metal to be protected from corrosion, is
immersed in an appropriate galvanic bath and connected as the
cathode. The counterelectrodes can be anodes of insoluble or,
preferably in the case of neutral or weakly acidic electrolytes,
soluble materials. Insoluble anodes are usually of graphite or
platinized titanium. It is convenient for soluble anodes to consist
of the metals of the alloy to be deposited, preferably at the
desired composition.
[0017] A temperature of about 20-70.degree. C. and a current
density of about 0.1-5 A/dm.sup.2 are considered boundary
conditions for deposition of the ternary tin-zinc alloys from the
electrolytes according to the invention. Deposition rates of about
0.05-1 .mu.m/minute are attained.
[0018] An alkaline electrolyte according to the invention can have
the following typical ranges of compositions:
[0019] 10-50 g/l tin as the sulfate or chloride, or sodium or
potassium stannate
[0020] 1-10 g/l zinc as the sulfate, chloride, hydroxide or
oxide
[0021] 0.1-10 g/l cobalt, nickel, or iron as the sulfate
[0022] 1-20 g/l potassium or sodium hydroxide
[0023] 10-200 g/l of complexing agent
[0024] 0.1-10 g/l of a wetting agent
[0025] 0.1-5 g/l of a brightener
[0026] The galvanic deposition of the alloy is accomplished at
temperatures in the range of 40-70.degree. C. and at current
densities of 1-5 A/dm.sup.2 at deposition rates of 0.15-0.3
.mu.m/minute. Graphite or platinized titanium can be used as
anodes.
[0027] Organic acids and their salts, phosphonic acids,
phosphonates, gluconates, glucoheptonic acids, glucoheptonates and
ethylenediaminetetraacetic acid can be used as complexing agents.
Surfactants, multifunctional alcohols, and betaines can be used as
wetting agents and brighteners in the corresponding media.
[0028] The composition of the alloy layer can be varied by altering
the proportions of the individual components in the bath. For
instance, increasing the hydroxide content reduces the tin content,
with corresponding increase of the other two metals in the
coating.
[0029] Increasing the proportion of the complexing agent reduces
the zinc content and increases the tin content in the coating.
These changes have practically no effect on the third alloying
metal.
[0030] A neutral electrolyte according to the invention can have
the following typical ranges of compositions:
[0031] 10-40 g/l tin as the sulfate, or as sodium or potassium
stannate
[0032] 0.5-10 g/l zinc as the sulfate, chloride, hydroxide or
oxide
[0033] 0.1-10 g/l cobalt, nickel or iron as the sulfate, chloride,
hydroxide or oxide
[0034] 50-200 g/l tetrasodium pyrophosphate
[0035] 1-20 g/l potassium hydroxide or sodium hydroxide
[0036] 10-200 g/l complexing agent
[0037] 0.1-10 g/l wetting agent
[0038] 0.1-5 g/l brightener
[0039] The electrolytic deposition of the alloy is accomplished at
temperatures from 40 to 70 .degree. C., and at current densities of
0.5-3 A/dm.sup.2, with deposition rates of 0.05-0.3 .mu.m/minute.
Graphite or platinized titanium are used as the anode. It is also
possible to use soluble anodes.
[0040] The proportions in the alloy composition can be varied by
varying the coating parameters.
[0041] A weakly acidic electrolyte according to the invention can
have the following typical ranges of compositions:
[0042] 1-10 g/l tin as the sulfate or chloride
[0043] 1-10 g/l zinc as the sulfate, chloride, hydroxide or
oxide
[0044] 1-20 g/l cobalt, nickel or iron as the sulfate, chloride,
hydroxide or carbonate
[0045] 5-200 g/l of a carboxylic acid salt
[0046] 5-50 g/l of a buffer
[0047] 1-30 g/l sodium chloride
[0048] 1-20 g/l wetting agent
[0049] 0.1-5 g/l brightener
[0050] The electrolytic deposition of the alloy is accomplished at
temperatures of 20 to 70.degree. C. at current densities of 0.5-5
A/dm.sup.2, with deposition rates of 0.1-1 .mu.m/minute. Graphite
or platinized titanium can be used as the anode. It is also
possible to use soluble anodes. Boric acid, for example, can be
used as the buffer.
[0051] The proportions in the alloy composition can be adjusted by
changing the coating parameters (concentrations of the components
in the solution, working parameters). For example, increasing the
current density increases the proportion of zinc and nickel, cobalt
or iron in the alloy and reduces the proportion of tin. Variation
of the temperature in the specified range causes only insignificant
changes of the composition of the alloy layer.
[0052] The ternary tin-zinc alloys according to the invention have
very favorable material properties. On the basis of those
properties, they can be used as an independent material, but also,
especially, as coatings on substrates in various manners.
[0053] In general, the ternary tin-zinc alloys have particularly
high resistance to corrosion, which is most strongly expressed in
the SnZnNi and SnZnCo systems. Therefore those alloys are
particularly suitable for anticorrosion layers on ferrous
materials. Accordingly, the corresponding electrolyte solutions can
be used preferentially to produce corrosionresistant layers on
ferrous materials. Iron sheets, coated in this manner, combined
with the usual passivation by chromating or chromiting, without
other treatment, attain resistance to appearance of red rust of
more than 3,000 hours.
[0054] Other advantageous properties can be controlled by selection
of the specific third alloying element. The properties of the
ternary tin-zinc alloy coatings according to the invention can be
optimized, depending on the choice of the third alloying element.
Table 1 shows an overview of the preferred third alloying element
if either good corrosion resistance, hardness, wear resistance or
weldability is desired.
1 TABLE 1 Corrosion Hardness Wear Weldability SnZnNi + - + - SnZnFe
- + - + SnZnCo + + - +
[0055] Of the three alloy systems, the SnZnFe and SnZnCo alloys
attain the highest hardnesses. SnZnNi coatings have the highest
resistances to wear. Such alloy coatings can, therefore, be used
advantageously as wear-prevention layers in cases of mechanical
stress. SnZnFe and SnZnCo coatings can be welded particularly well,
and so are desirable as weldable coatings and contact surfaces in
electronics. Table 2 shows the corresponding data for alloy systems
selected as examples.
2 TABLE 2 Coating SnZnNi SnZnFe SnZnCo Composition Sn 44% Sn 52% Sn
46% Zn 56% Zn 44% Zn 51% Ni 0.2% Fe 4% Co 3% Hardness 50 165 179
(HV 0.025) Wear 4.9 9.1 7.2 (mg weight lost per 1000 strokes
according to Bosch-Weinmann) Weldability 0.3-0.4 0.8-1.2 0.3-0.6
(ZCT in seconds)
[0056] Aside from these areas of use determined by function, the
ternary tin-zinc alloys according to the invention can also be used
as final decorative coatings. For instance, the three alloy systems
have interesting and appealing colors in the blue range, depending
on the selection of the third alloying element.
EXAMPLE 1
[0057] An alkaline electrolyte for depositing an alloy consisting
of 45% by weight Sn, 52% by weight Zn and 3% by weight cobalt has
the following composition:
[0058] 30 g/l tin as sodium stannate
[0059] 2.4 g/l zinc as zinc oxide
[0060] 1 g/l cobalt as cobalt sulfate
[0061] 8 g/l potassium hydroxide
[0062] 50 g/l sodium citrate
[0063] 100 ml/l sodium phosphonate
[0064] 2.5 ml/l anionic surfactant
[0065] 1 g/l butynediol
[0066] This gives a pH of 11. The coating composition indicated
above can be produced with this electrolyte at a temperature of
60.degree. C. and current densities of 1-2 A/dm.sup.2. In this
case, about 0.2 .mu.m of coating layer is built up per minute. The
density of the alloy layer is 7.27 g/cm.sup.3.
[0067] Iron plates coated with this alloy at a thickness of 8
.mu.m, after chromating (based on Cr.sup.+6) show the following
resistance in the salt mist test of DIN 50021-SS:
[0068] First appearance of white rust in the time period 1800-3000
hours.
[0069] The test was terminated after 3000 hours, as no red rust had
appeared by that time.
EXAMPLE 2
[0070] A neutral electrolyte for depositing an alloy consisting of
48% by weight tin, 49% by weight zinc and 3% by weight cobalt has
the following composition:
[0071] 25 g/l tin as tin sulfate
[0072] 2.4 g/l zinc as zinc oxide
[0073] 1 g/l cobalt as cobalt sulfate
[0074] 130 g/l tetrasodium pyrophosphate
[0075] 2.5 ml/l anionic surfactant
[0076] 1 g/l butynediol
[0077] This solution has a pH of 8.5. The coating composition
indicated above can be produced with this electrolyte at a
temperature of 60.degree. C. and current densities of 0.5-1
A/dm.sup.2. 0.15 .mu.m of coating is built up per minute. The
density of the alloy layer is 7.27 g/cm.sup.3.
EXAMPLE 3
[0078] A weakly acidic electrolyte for depositing an alloy
consisting of 49.2% by weight Sn,
[0079] 50.5% by weight Zn and 0.3% by weight nickel has the
following composition:
[0080] 5 g/l tin as tin sulfate
[0081] 6.8 g/l zinc as zinc sulfate
[0082] 12 g/l nickel as nickel sulfate
[0083] 80 g/l sodium citrate
[0084] 25 g/l boric acid
[0085] 10 ml/l anionic surfactant
[0086] 1 ml/l beta-naphthol ethoxylate
[0087] This solution has a pH of 4.5. The coating composition
indicated above can be produced with this electrolyte at a
temperature of 40.degree. C. and a current density of 1.5
A/dm.sup.2. In this case, about 0.4 .mu.m of the alloy layer is
produced per minute. The density of the alloy layer is 7.2
g/cm.sup.3.
EXAMPLE 4
[0088] A weakly acidic electrolyte for depositing an alloy
consisting of 52% by weight Sn, 44% by weight Zn, and 4% by weight
iron has the following composition:
[0089] 5 g/l tin as tin sulfate
[0090] 6.8 g/l zinc as zinc sulfate
[0091] 10 g/l iron as iron sulfate
[0092] 80 g/l sodium citrate
[0093] 25 g/l boric acid
[0094] 10 ml/l anionic surfactant
[0095] 1 ml/l beta-naphthol ethoxylate
[0096] The pH of this solution is 4.4. This electrolyte can produce
the layer composition stated above at a temperature of 40.degree.
C. and a current density of 1.5 A/dm.sup.2. In this case, about 0.4
.mu.m of the alloy layer is deposited per minute. The density of
the alloy layer is 7.25 g/cm.sup.3.
* * * * *