U.S. patent application number 13/796052 was filed with the patent office on 2017-02-23 for processes and compositions for improving corrosion performance of zirconium oxide pretreated zinc surfaces.
This patent application is currently assigned to HENKEL AG & CO. KGAA. The applicant listed for this patent is HENKEL AG & CO. KGAA. Invention is credited to Alvaro Bobadilla, Michael Febbraro, Bruce H. Goodreau, Edis Kapic.
Application Number | 20170050215 13/796052 |
Document ID | / |
Family ID | 48903159 |
Filed Date | 2017-02-23 |
United States Patent
Application |
20170050215 |
Kind Code |
A9 |
Kapic; Edis ; et
al. |
February 23, 2017 |
PROCESSES AND COMPOSITIONS FOR IMPROVING CORROSION PERFORMANCE OF
ZIRCONIUM OXIDE PRETREATED ZINC SURFACES
Abstract
A method of improving corrosion resistance of a metal substrate
comprising a zinc surface coated with zirconium oxide conversion
coating by, prior to conversion coating, contacting the zinc
surface with a composition comprising: a) iron(III) ions, b) a
source of hydroxide ion; c) at least one complexing agent selected
from organic compounds which have at least one functional group
--COOX, wherein X represents either a H or an alkali and/or
alkaline earth metal; d) 0.0 to about 4 g/l cobalt (II) ions; and
optionally e) a source of silicate: wherein the composition has a
pH of at least 10.
Inventors: |
Kapic; Edis; (Sterling
Heights, MI) ; Goodreau; Bruce H.; (Romeo, MI)
; Bobadilla; Alvaro; (Royal Oak, MI) ; Febbraro;
Michael; (Ray Township, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HENKEL AG & CO. KGAA |
Duesseldorf |
|
DE |
|
|
Assignee: |
HENKEL AG & CO. KGAA
Duesseldorf
DE
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20130202911 A1 |
August 8, 2013 |
|
|
Family ID: |
48903159 |
Appl. No.: |
13/796052 |
Filed: |
March 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US2012/024311 |
Feb 8, 2012 |
|
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13796052 |
|
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61440657 |
Feb 8, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 22/34 20130101;
C23C 22/80 20130101; C23C 22/83 20130101; C23C 22/82 20130101; C23F
11/06 20130101; C23C 22/60 20130101; B05D 3/002 20130101; Y10T
428/12611 20150115; C23C 22/78 20130101; B32B 15/04 20130101; C23C
22/73 20130101; C23C 22/62 20130101; C23C 22/66 20130101 |
International
Class: |
B05D 3/00 20060101
B05D003/00; B32B 15/04 20060101 B32B015/04 |
Claims
1. A method for improving corrosion performance of a metal
substrate comprising steps of:) 1. providing a metal substrate
comprising at least one zinc or zinc alloy surface; 2. contacting
said surface with an alkaline pre-rinse composition comprising: a)
iron(III) ions, b) a source of hydroxide ion; c) at least one
complexing agent selected from organic compounds which have at
least one functional group --COOX, wherein X represents either a H
or an alkali and/or alkaline earth metal; d) 0.0 to about 4 g/l
cobalt (II) ions; and optionally e) a source of silicate: wherein
the composition has a pH of at least 10; 3. optionally rinsing said
surface; 4. applying to the metal substrate a zirconium-based metal
pretreatment coating composition comprising zirconium, thereby
forming a pretreatment coating on the metal substrate; and 5.)
optionally applying a paint to the metal pretreatment coated metal
substrate.
2. The method of claim 1 wherein contact time of step 2.) is from
10 to 60 seconds and the alkaline pre-rinse composition has a
temperature of 85 to 125 degrees F.
3. The method of claim 1 wherein the cobalt (II) ions are present
in an amount of 1 ppm up to the solubility limit of the cobalt (II)
ions.
4. The method of claim 1 wherein the alkaline pre-rinse composition
is phosphate-free.
5. The method of claim 1 wherein the zirconium-based metal
pretreatment coating composition further comprises fluoride and a
chelating agent.
6. The method of claim 1 wherein the zirconium-based metal
pretreatment coating composition comprises 50 to 300 ppm of
dissolved Zr, 0 to 50 ppm of dissolved Cu, 0 to 100 ppm of
SiO.sub.2, 150 to 2000 ppm of total Fluoride, 10 to 100 ppm of free
Fluoride and optionally a chelating agent.
7. A coated metal article comprising: A) a steel substrate; B) a
first layer comprising a zinc or zinc alloy metal surface deposited
on the steel substrate; C) a second layer generated on said zinc or
zinc alloy metal surface by contact with a composition of claim 1;
D) a third layer comprising zirconium oxide deposited by contacting
the second layer with a zirconium-based metal pretreatment coating
composition comprising dissolved Zr; and E) a fourth layer
comprising at least one paint; wherein said coated metal article
has better resistance to cyclic corrosion than a comparative metal
article coated with the first layer, the zirconium-based metal
pretreatment coating composition comprising dissolved Zr and the
paint in the absence of C).
8. An aqueous alkaline composition comprising: a) iron(III) ions,
b) a source of hydroxide ion; c) at least one complexing agent
selected from organic compounds which have at least one functional
group --COOX, wherein X represents either a H or an alkali and/or
alkaline earth metal; d) cobalt (II) ions; and optionally: e) a
source of silicate: wherein the composition has a pH of at least
10.
9. The composition of claim 8 wherein the composition is
phosphate-free.
10. The composition of claim 8 wherein the cobalt (II) ions are
present in an amount of 1 ppm up to the solubility limit of the
cobalt (II) ions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] NONE
FIELD OF THE INVENTION
[0002] This invention relates to methods of improving corrosion
performance of zirconium oxide conversion coatings deposited on
zinc-containing surfaces by pre-treating the zinc-containing
surfaces with a composition containing cobalt and/or iron before
contacting with a zirconium oxide forming conversion coating
composition. More particularly, the invention relates to a
multi-step coating process and bath compositions used therein which
provide improved corrosion performance, particularly cyclic
corrosion, on zinc-containing surfaces, such as Hot Dip Galvanized
(hereinafter referred to as HDG) and Electro Galvanized
(hereinafter referred to as EG) substrates. The invention also
provides concentrate compositions for use in the bath, methods of
making and using the concentrate and bath, as well as metal
articles comprising a coating according to the invention.
BACKGROUND OF THE INVENTION
[0003] There are currently in the market a number of zirconium
oxide depositing conversion coating products intended to replace
zinc phosphate products in automotive assembly lines. These known
products are used to coat ferrous metal surfaces as well as
aluminum and zinc containing surfaces.
[0004] An issue for current zirconium oxide conversion coating
processes is that they do not provide as good corrosion protection
as conventional zinc phosphate processes under some circumstances
and on some substrates.
[0005] One particular problem has been that current processes for
zirconium oxide conversion coating of zinc-containing substrates,
in particular HDG and EG, do not provide coated metal articles that
meet certain automotive testing requirements. Hot Dip Galvanized
(HDG) and Electro Galvanized (EG) steel substrates treated with a
commercially available zirconium oxide pretreatment baths exhibited
weaker performance in two separate automotive industry corrosion
tests when compared to the conventional Bonderite.RTM. zinc
phosphate treatments currently used in the automotive industry.
Thus there is a need for a process of coating these substrates with
a zirconium oxide conversion coating that provides for improved
corrosion performance of zirconium oxide conversion coatings on HDG
and EG substrates.
[0006] The instant invention solves one or more to the above
problems in zirconium oxide coating processes by including at least
one pre-treating step, where the zinc-containing surfaces are
contacted with a composition, for example a cleaner and/or a
pre-rinse, containing cobalt and/or iron, in the zirconium oxide
conversion coating processes.
SUMMARY OF THE INVENTION
[0007] In one embodiment, the invention provides a method for
improving corrosion performance of a metal substrate comprising
steps of: [0008] 1.) providing a metal substrate comprising at
least one zinc or zinc alloy surface; [0009] 2.) contacting said
surface with an alkaline pre-rinse composition comprising: [0010]
a) iron(III) ions, [0011] b) a source of hydroxide ion; [0012] c)
at least one complexing agent selected from organic compounds which
have at least one functional group --COOX, wherein X represents
either a H or an alkali and/or alkaline earth metal; [0013] d) 0.0
to about 4 g/l cobalt (II) ions; and [0014] optionally [0015] e) a
source of silicate: [0016] wherein the composition has a pH of at
least 10; [0017] 3.) optionally rinsing said surface; [0018] 4.)
applying to the metal substrate a zirconium-based metal
pretreatment coating composition comprising zirconium, thereby
forming a pretreatment coating on the metal substrate; and [0019]
5.) optionally applying a paint to the metal pretreatment coated
metal substrate.
[0020] In another embodiment the invention provides the aqueous
alkaline composition s utilized in the method. These compositions
and methods may provide an aqueous alkaline composition containing
cobalt (II) ions present in an amount of 1 ppm up to the solubility
limit of the cobalt (II) ions, and as shown in the Examples may be
phosphate-free, with low levels or no silicates.
[0021] In one embodiment of the method contact time of step 2.) is
from 10 to 60 seconds and the alkaline pre-rinse composition has a
temperature of 85 to 125 degrees F.
[0022] In another embodiment the compositions and methods may
include zirconium-based metal pretreatment coating composition
further comprising fluoride and a chelating agent. In one
embodiment, the zirconium-based metal pretreatment coating
composition comprises 50 to 300 ppm of dissolved Zr, 0 to 50 ppm of
dissolved Cu, 0 to 100 ppm of SiO2, 150 to 2000 ppm of total
Fluoride, 10 to 100 ppm of free Fluoride and optionally a chelating
agent.
[0023] In another aspect of the invention, a coated metal article
is provided which comprises: [0024] A) a steel substrate; [0025] B)
a first layer comprising a zinc or zinc alloy metal surface
deposited on the steel substrate; [0026] C) a second layer
deposited on said zinc or zinc alloy metal surface by contact with
a composition of the invention; [0027] D) a third layer comprising
zirconium oxide deposited by contacting the second layer with a
zirconium-based metal pretreatment coating composition comprising
dissolved Zr; and [0028] E) a fourth layer comprising at least one
paint; [0029] wherein said coated metal article has better
resistance to cyclic corrosion than a comparative metal article
coated with the first layer, the zirconium-based metal pretreatment
coating composition comprising dissolved Zr and the at least one
paint in the absence of C).
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 shows a series of histogram comparison graphs of
performance in cyclic corrosion test GM9540P by four different
substrates treated according to three processes as described in
Example 1. FIG. 1A shows corrosion test performance of hot-dip
galvanized (HDG) steel panels; FIG. 1B shows corrosion test
performance of electro galvanized (EG) steel panels; FIG. 1C shows
corrosion test performance of aluminum alloy panels (Al6111); and
FIG. 1D shows corrosion test performance of cold rolled steel (CRS)
panels.
[0031] FIG. 2 shows a series of histogram comparison graphs of
performance in cyclic corrosion test APGE by four different
substrates treated according to three processes as described in
Example 2. FIG. 2A shows corrosion test performance of hot-dip
galvanized (HDG) steel panels; FIG. 2B shows corrosion test
performance of electro galvanized (EG) steel panels; FIG. 2C shows
corrosion test performance of aluminum alloy panels (Al6111); and
FIG. 2D shows corrosion test performance of cold rolled steel (CRS)
panels.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0032] In seeking to modify the HDG and EG surfaces, which are
mostly zinc, to improve corrosion performance Applicants have
developed alkaline compositions containing cobalt and/or iron,
useful as pre-rinses and cleaners, for pretreating HDG and EG
substrates prior to contacting the substrates with zirconium oxide
generating conversion coating baths, which provide improved
corrosion resistance to the zirconium oxide coated substrate.
[0033] One aspect of the invention comprises an aqueous alkaline
composition, which comprises, consists essentially of, or consists
of: [0034] a) iron(III) ions, [0035] b) a source of hydroxide ion;
[0036] c) at least one complexing agent selected from organic
compounds which have at least one functional group --COOX, wherein
X represents either a H or an alkali and/or alkaline earth metal;
and optionally [0037] d) 0.0 to about 4 g/l cobalt (II) ions;
[0038] e) a source of silicate: [0039] wherein the composition has
a pH of at least 10.
[0040] Also provided are processes of coating a metal substrate
comprising at least one zinc or zinc alloy surface, whereby
corrosion performance of the metal substrate is improved comprising
the steps of: [0041] 1) providing a metal substrate, e.g. a steel
substrate, comprising at least one zinc or zinc alloy surface;
[0042] 2) contacting said surface with a composition comprising:
[0043] a) iron(III) ions, [0044] b) a source of hydroxide ion;
[0045] c) at least one complexing agent selected from organic
compounds which have at least one functional group --COOX, wherein
X represents either a H or an alkali and/or alkaline earth metal;
and optionally [0046] d) 0.0 to about 4 g/l cobalt (II) ions;
[0047] e) a source of silicate: [0048] wherein the composition has
a pH of at least 10; [0049] 3.) optionally rinsing said surface;
[0050] 4.) applying to the metal substrate a zirconium-based metal
pretreatment coating composition comprising 50 to 300 ppm of
dissolved Zr, 0 to 50 ppm of dissolved Cu, 0 to 100 ppm of
SiO.sub.2, 150 to 2000 ppm of total Fluoride, 10 to 100 ppm of free
Fluoride and optionally a chelating agent, thereby forming a
pretreatment coating on the metal substrate; and [0051] 5.)
optionally applying a paint to the metal pretreatment coated metal
substrate.
[0052] HDG and EG steel substrates contacted with cobalt and/or
iron containing compositions, e.g. alkaline cleaners and/or
pre-rinses, prior to coating with commercially available zirconium
oxide pretreatment bath showed improved corrosion performance
cyclic corrosion tests.
[0053] A typical process for producing a finished zirconium oxide
coated substrate having a zinc-containing surface will include the
following steps in order: application of a cleaner solution; rinse
in warm water; application of an anti-corrosion conversion coating;
deionized water rinse; compressed air drying of the substrate;
application of an initial paint layer by electrodeposition
generally with baking; application of a primer layer; application
of a basecoat paint layer; and finally application of a clearcoat
paint layer. The term "paint" being understood to mean any one of
these layers and combinations thereof. In the instant invention,
the process is changed by either using a cleaner solution according
to the invention that comprises cobalt and/or iron, adding an
alkaline pre-rinse step between cleaning and anti-corrosion
conversion coating, wherein the alkaline pre-rinse contain cobalt
and/or iron or both. The inclusion of cobalt and/or iron provided
unexpected changes in corrosion performance to the zirconium oxide
conversion coated zinc surface.
[0054] Generally, cleaner solutions are comprised of components to
achieve alkaline pH, generally providing high levels of silicate
and/or phosphate, for example 2-20 wt %, and have no actively added
iron or cobalt in the cleaner, unlike those described as preferred
for the present invention. In one embodiment, cleaner compositions
of the invention may be applied by spraying onto the substrate
followed by an immersion in the cleaner bath with agitation. In
another embodiment, the substrate may be immersed in the inventive
composition, removed and optionally rinsed with distilled water,
prior to conversion coating.
[0055] In one embodiment, the present inventors have surprisingly
found that modification of an alkaline cleaner composition by
addition of cobalt and/or iron can lead to enhanced corrosion
resistance of zinc-containing surfaces that are subsequently coated
with an anti-corrosion pretreatment, for example a zirconium oxide
conversion coating, and painted per industry standards.
[0056] Compositions, e.g. aqueous cleaners and pre-rinses,
according to the invention comprise: [0057] a) iron(III) ions,
[0058] b) a source of hydroxide ion; [0059] c) at least one
complexing agent selected from organic compounds which have at
least one functional group --COOX, wherein X represents either a H
or an alkali and/or alkaline earth metal; and optionally [0060] d)
0.0 to about 4 g/l cobalt (II) ions; [0061] e) a source of
silicate: [0062] wherein the composition has a pH of at least
10.
[0063] Component a) iron(III) ions is generally present in an
amount, in increasing order of preference, of about 5, 10, 15, 20,
25, 30, 40, 50, 60, 70, 80, 90, or 100 ppm and at most in
increasing order of preference about 500, 400, 350, 300, 250, 200,
150 ppm. Suitable sources of the iron (III) ions are water soluble
or alkali soluble salts of iron, such as by way of non-limiting
example ferric nitrate, ferric sulfate, ferric ammonium citrate,
ferric citrate, ferric ammonium sulfate and ferric chloride. Ferric
nitrate and ferric sulfate are preferred.
[0064] Component b) the source of hydroxide ion is generally
present in an amount, in increasing order of preference, of about
0.5, 0.75, 1, 1.5, 2, 2.5 g/l and at most in increasing order of
preference about 4.0, 3.5, 3.0, 2.75 g/l. Greater amounts of
hydroxide source may be used provided that the composition does not
cause undue etching of the substrate. Suitable sources are water
soluble alkali metal or ammonium hydroxide salts, preferably NaOH
or KOH.
[0065] Component c) the one or more complexing agents are generally
present in an amount, in increasing order of preference, of about
30, 40, 50, 60, 70, 80, 90, or 100 ppm and at most in increasing
order of preference about 500, 400, 350, 300, 250, 200, 150
ppm.
[0066] Suitable sources of complexing agents are those selected
from water soluble organic compounds which have at least one
functional group --COOX, wherein X represents either a H or an
alkali and/or alkaline earth metal. In one embodiment, the
complexing agents are selected from mono- and/or di-carboxylic
acids and salts thereof, optionally having one or more hydroxide
moieties.
[0067] Optional component d) cobalt (II) ions concentration ranges
from 0.0 to about 4 g/l cobalt (II) ions. If present, cobalt is
generally advantageous in an amount, in increasing order of
preference, of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16,
20, 25, 50 ppm and at most in increasing order of preference of
about 200, 150, 100, 75, 60 ppm. Greater amounts may be added up to
the solubility limit of the cobalt. Suitable sources of cobalt ions
are those compounds of cobalt that are water and or alkali soluble,
for example cobalt nitrate, cobalt sulfate, cobaltous citrate,
cobalt oxide, cobalt chloride. Cobalt nitrate and sulfate are
preferred.
[0068] Optional Component e) the source of silicate is generally
present in an amount of sufficient to provide silicate in an
amount, in increasing order of preference, of about 30, 40, 50, 60,
70, 80, 90, 100, 150, 200, 250, or 300 ppm and at most in
increasing order of preference about 1000, 900, 800, 700, 600, 500,
400, or 350 ppm. Suitable sources of silicate include water soluble
silicates, such as alkali metal silicates. Sodium silicate and
potassium silicate are preferred.
[0069] The compositions of the invention are alkaline and may have
a pH of at least in increasing order of preference 10, 10.5, 11,
11.5, 12 and at most in increasing order of preference 13.5, 13,
12.5. Generally, this pH is obtained by presence in the bath of
about 0.5-3 g/L OH.
[0070] Use conditions for compositions according to the invention
are at temperatures, in increasing order of preference, of about
85, 90, 95, 100, 105, 110, 120.degree. F. and at most in increasing
order of preference about 125, 130, 135, 140, 145, 150, 155,
160.degree. F., that is about 30, 35, 40, 45, 50, 55, 60, 65 or
70.degree. C.
[0071] The zinc or zinc alloy surface to be coated with a zirconium
oxide coating is typically optionally cleaned with a conventional
cleaner and then contacted with a composition according to the
invention for a period of 10, 15, 20, 25, 30, 45, 60 seconds,
followed by rinsing. The full process can be seen in the examples
below.
[0072] The zirconium containing pretreatment coating may be applied
via spray, immersion bath or both for a period of time generally
ranging from 30 to 180 seconds. Typically the exposure occurs at
ambient temperature, and may be at temperatures of about
10-50.degree. C., usually 20-30.degree. C. or 25.degree. C.
[0073] Concentrations given above are those for the working bath,
except where indicated otherwise. Concentrates for making the
working bath may be provided at concentrations of 1.times. to
20.times. of the concentrations given for the working bath,
provided that the increase in concentration does not cause
precipitation or instability of the concentrate. Desirably the
concentrates are stable if they do not precipitate or coagulate
upon storage at ambient temperature for at least 30, 45, 60, 90,
120 days.
[0074] Other than in the operating examples, or where otherwise
indicated, all numbers expressing quantities of ingredients,
reaction conditions, or defining ingredient parameters used herein
are to be understood as modified in all instances by the term
"about". Unless otherwise indicated, all ratios and percentages are
percent by weight.
EXAMPLES
[0075] Laboratory test results showed that an alkaline pre-rinse
according to the invention improved the cyclic corrosion
performance of EG and HDG coated with a zirconium oxide conversion
coating.
Example 1
[0076] The processes tested included:
TABLE-US-00001 Process 1 Bonderite 958 (commercially available zinc
phosphate: control) Process 2 TD-1323-HB/HC standard process
(control) Process 3 Alkaline Co/Fe pre-rinse + TD-1323-HB/HC
Process 4 Fe containing cleaner + TD-1323-HB/HC Process 5 Co/Fe
containing cleaner + TD-1323-HB/HC * TD-1323-HB/HC is a
commercially available zirconium oxide pretreatment bath.
[0077] Standard (12''.times.4'') test panels were obtained from ACT
Laboratories, Hillsdale, Michigan USA; Cold Rolled Steel (CRS),
Electro-Galvanized Steel (EG), Aluminum 6111 (AL6111), Hot Dip
Galvanized Steel (HDG). Panels of each of the four substrates were
treated according to one of the below processes. The process steps
for testing of the pre-rinse were as follows:
[0078] Process 1 (Control) Bonderite 958 [0079] 1. Parco Cleaner
1533--120 sec. (Spray) [0080] 2. Warm Water Rinse--30 sec. (Spray)
[0081] 3. Fixodine Z8--30 sec. (Spray) [0082] 4. Bonderite 958
(zinc phosphating)--120 sec. (Immersion) [0083] 5. Cold Water
Rinse--30 sec. (Spray) [0084] 6. Parcolene 91--60 sec. (Spray)
[0085] 7. DIW Rinse--30 sec. (Spray)
[0086] Process 2 (Control) TD-1323-HB [0087] 1. Parco Cleaner
1533--120 sec. (Spray) [0088] 2. Warm Water Rinse--30 sec. (Spray)
[0089] 3. DIW Rinse--30 sec. (Spray) [0090] 4. TD-1323-HB--90 sec.
(Immersion) [0091] 5. Cold Water Rinse--30 sec. (Spray) [0092] 6.
DIW Rinse--30 sec. (Spray)
[0093] Process 3 TD-1323-HB+Alkaline Co/Fe Pre-Rinse [0094] 1.
Parco Cleaner 1533--120 sec. (Spray) [0095] 2. Warm Water Rinse--30
sec. (Spray) [0096] 3. Alkaline Co/Fe pre-rinse 9% v/v of
concentrate--15 sec. (Spray) [0097] 4. Warm Water Rinse--30 sec.
(Spray) [0098] 5. DIW Rinse--30 sec. (Spray) [0099] 6.
TD-1323-HB--90 sec. (Immersion) [0100] 7. Cold Water Rinse--30 sec.
(Spray) [0101] 8. DIW Rinse--30 sec. (Spray)
TABLE-US-00002 [0101] TABLE 1 Alkaline Co/Fe Pre-rinse Concentrate
Water tap 50.921 Chelant (complexing agent) 1.979 Sodium salt of
carboxylic acid Cobalt(II)nitrate solution (13 wt % Co) 1.900
Iron(III)nitrate 9H.sub.2O (14 wt % Fe) 1.300 Sodium hydroxide 50%
Solution 43.900 Total 100.000
[0102] The test panels were painted, the paint was allowed to cure
and the panels were subjected to either 40 cycles of GM9540P
corrosion testing or 50 cycles of APGE testing. Both of these
cyclic corrosion tests are standard automotive industry cyclic
corrosion tests known to those of skill in the art.
TABLE-US-00003 TABLE 2 APGE Results Corrosion (mm) Average Maximum
Process 1 (Control) Bonderite 958 HDG 5.4 2.8 EG 9.5 3.8 CRS 0.6
0.7 AL6111 0.8 5.7 Process 2 (Control) TD-1323-HB HDG 6.1 11.0 EG
4.7 7.2 CRS 9.2 12.3 AL6111 0.6 4.3 Process 3 TD-1323-HB + Alkaline
Pre-rinse HDG 2.7 3.6 EG 1.7 2.7 CRS 6.8 9.8 AL6111 2.0 9.1 GM9540P
Results Corrosion (mm) Average Maximum Process 1 (Control)
Bonderite 958 HDG 1.4 1.8 EG 1.7 1.8 CRS 2.6 2.8 AL6111 0.5 0.6
Process 2 (Control) TD-1323-HB HDG 2.3 3.0 EG 2.6 3.1 CRS 6.0 6.6
AL6111 0.6 0.9 Process 3 TD-1323-HB + Alkaline Pre-rinse HDG 1.2
1.5 EG 2.5 2.9 CRS 5.0 5.2 AL6111 0.3 0.5
[0103] The above corrosion results showed better corrosion
resistance for HDG and EG, as shown by less scribe creep, as
compared to the zirconium oxide control, and in several tests did
as well or better than the zinc phosphate (Bonderite 958), which is
a commonly used conversion coating for automotive. FIGS. 1 and 2
provide a graphic representation of improved results of inventive
Process 3, as compared to Process 2 where the comparative metal
article was coated with zinc, the zirconium-based metal
pretreatment coating composition comprising dissolved Zr
(TD-1323-HB) and paint in the absence of the alkaline pre-rinse.
The testing also showed that the pre-rinse did not negatively
affect corrosion resistance of the CRS panels, which is important
to usefulness in using the same process for CRS and zinc surfaces
and for metal articles made of CRS and zinc surfaces.
Example 2
[0104] Several proposed alkaline pre-rinse formulations were
tested. The concentrate formulas are shown in Table 3 below.
TABLE-US-00004 TABLE 3 Chemical 1A 2A 3A 4A 5A 6A DI Water 50.9
48.9 52.8 25.8 23.8 27.7 Sodium Gluconate 2.0 4.0 2.0 2.0 4.0 2.0
Cobalt Nitrate Solution 1.9 1.9 0.0 1.9 1.9 0 (13% Co) Ferric
Nitrate (14% Fe) 1.3 1.3 1.3 1.3 1.3 1.3 Sodium Hydroxide 43.9 43.9
43.9 50% Solution Potassium Hydroxide 68.6 68.6 68.6 45% Solution
Sodium Silicate 0.4 0.4 0.4 Total wt % 100.0 100.0 100.0 100.0
100.0 100.0
[0105] Formulas 1A, 2A, 4A and 5A utilized Co and Fe, Formulas 3A
and 6A used only Fe. Formulas 4A-6A used added silicate, Formulas
1A-6A were phosphate-free. Formulas 1A and 2A were comparable as
were Formulas 4A and 5A, but for different levels of complexing
agent.
[0106] Standard (12''.times.4'') test panels were obtained from ACT
Laboratories, Hillsdale, Michigan USA; Cold Rolled Steel (CRS),
Electro-Galvanized Steel (EG), Aluminum 6111 (AL6111), Hot Dip
Galvanized Steel (HDG). The process steps are outlined in Table 5,
below. For each concentration and time in Table 4, below, three
panels of each of the four substrates were treated.
TABLE-US-00005 TABLE 4 Pre-rinse Time 1 (in pre- Time 2 (in Formula
bath % rinse) pre-rinse) 1-A 1 15 sec 30 sec 4 15 sec 30 sec 7 15
sec 30 sec 10 15 sec -- 2-A 1 15 sec 30 sec 4 15 sec 30 sec 7 15
sec 30 sec 10 15 sec -- 3-A 1 15 sec 30 sec 4 15 sec 30 sec 7 15
sec 30 sec 10 15 sec -- 4-A 1 15 sec 30 sec 4 15 sec 30 sec 7 15
sec 30 sec 10 15 sec -- 5-A 1 15 sec 30 sec 4 15 sec 30 sec 7 15
sec 30 sec 10 15 sec -- 6-A 1 15 sec 30 sec 4 15 sec 30 sec 7 15
sec 30 sec 10 15 sec --
TABLE-US-00006 TABLE 5 Processes steps: Pretreatment Process
Bonderite Standard Alkaline 958 Zinc Zr oxide Pre-rinse + phosphate
coating process Standard Zr oxide Process Step (Control) (Control)
coating process Cleaning (PCL 1533) - 120 sec. 120 sec. 120 sec.
Spray Warm Tap Water Rinse - 30 sec. 30 sec. 15 sec. Spray
Conditioning (Fix-Z8) - 30 sec. -- -- Spray Alkaline Pre-rinse - --
-- 15 or 30 sec. Immersion Warm Tap Water Rinse - -- -- 30 sec.
Spray DI Water Rinse - Spray -- 30 sec. 30 sec. Pretreatment -
Immersion 120 sec. 90 sec. 60 sec. DI Water Rinse - Spray 30 sec.
30 sec. 30 sec.
The test panels were e-coated wet-on-wet with DuPont's
Cormax.RTM.VI e-coat.
Process Baths' Conditions
Cleaning (all Processes):
[0107] Parco Cleaner 1533 bath was built according to
manufacturer's instructions, in 20 L spray tank. Free
Alkalinity=5.5.about.6.6, Total Alkalinity=5.8.about.7.5,
pH=11.2.about.12.3, Temperature=120.degree. F. (49.degree. C.).
Conditioning (for Bonderite.RTM.958 Process):
[0108] Fixodine Z8 bath was built at 1.2 g/L in 20 L spray tank.
Filterable Ti=6 ppm, Total Ti=9 ppm, pH.apprxeq.9.
Bonderite.RTM.958 Bath:
[0109] Free Acid=0.8, Total Acid=23.4, Accelerator=3.5, Free
F.sup.-=178 ppm, Zn=1000 ppm, Ni=900 ppm, Mn=570 ppm,
Temperature=120.degree. F. (49.degree. C.).
Zirconium Oxide Coating Bath:
[0110] Same formulation used to process control panels and alkaline
pre-rinsed panels:
[0111] Initial: Zr=159 ppm, Cu=24 ppm, pH=3.8.about.3.9, Free
F-=-95.about.-100 RmV. Zirconium oxide coating bath parameters used
for conversion coating were Zr 135-166 ppm, Cu 15 to 26 ppm, free
fluoride in the bath was maintained between -97 and -110 RmV
throughout the study, and pH was 3.75-4.25.
[0112] The alkaline pre-rinse bath conditions with each of the
alkaline pre-rinse variations are given in Table 6.
TABLE-US-00007 TABLE 6 Alkaline pre-rinse bath conditions for each
process variation. Alkaline Pre-rinse Bath Free Total Temperature
Variation Concentration Alkalinity Alkalinity pH (.degree. F.) 1A
1% 1.0 1.2 12.40 120 (15 sec.) 4% 4.3 4.6 12.88 120 7% 7.5 7.9
13.00 120 10% 10.8 13.0 13.30 120 1A 1% 1.0 1.3 12.20 120 (30 sec.)
4% 4.2 4.6 12.70 120 7% 7.4 7.9 12.89 120 2A 1% 1.0 1.2 12.22 120
(15 sec.) 4% 4.1 4.4 12.77 120 7% 7.2 7.6 12.97 120 10% 10.1 10.6
13.07 120 2A 1% 1.1 1.3 12.33 120 (30 sec.) 4% 4.5 4.9 12.98 120 7%
7.8 8.2 13.22 120 3A 1% 0.9 1 12.24 120 (15 sec.) 4% 3.4 3.5 12.78
120 7% 6 6.3 12.97 120 10% 8.3 8.6 13.07 120 3A 1% 1 1.3 12.35 120
(30 sec.) 4% 3.7 4 12.95 120 7% 6.5 6.8 13.14 120 4A 1% 0.9 1.1
12.25 120 (15 sec.) 4% 3.6 4.0 12.83 120 7% 6.4 6.9 13.07 120 10%
9.1 9.8 13.23 120 4A 1% 1.1 1.2 12.22 120 (30 sec.) 4% 3.8 4.1
12.87 120 7% 6.6 7 13.17 120 5A 1% 1.3 1.4 12.38 120 (15 sec.) 4%
4.6 4.9 13.06 120 7% 8.0 8.9 13.29 120 10% 11.3 12.4 13.50 120 5A
1% 1.2 1.4 12.58 120 (30 sec.) 4% 4.5 4.8 13.23 120 7% 7.8 8.3
13.47 120 6A 1% 1.3 1.4 12.43 120 (15 sec.) 4% 4.6 4.8 13.05 120 7%
8.3 8.6 13.40 120 10% 11.6 12.1 13.58 120 6A 1% 1.1 1.3 12.16 120
(30 sec.) 4% 4.5 4.7 12.86 120 7% 7.8 8.1 13.26 120
Corrosion Test Procedures
[0113] Ford APGE Cyclic Corrosion Testing (FLTM BI 123-01)-15
Cycles on CRS and 50 Cycles on EG, HDG, and AL6111.
[0114] General Motors Cyclic Corrosion Testing (GM9540P)-40 Cycles
on all substrates.
Corrosion Performance on EG:
[0115] For the APGE test; in most of the variations EG experienced
maximum corrosion of about 4-7 mm. There were a few instances were
the maximum corrosion went above 7 mm. Formula 1A at 30 seconds and
4% concentration=15.49 mm, Formula 2A at 30 seconds and 4%
concentration=12.00 mm, Formula 3A at 30 seconds and 7%
concentration=8.70 mm. The average corrosion values for these three
variations were comparable to other variations; all variations
ranging within 4.62 mm at 1% and 15 sec. to 1.70 at 7% for 30 sec.
Formula 2A at 15 seconds and 10% concentration, and at 30 seconds
and 7% concentration showed the best results with maximum corrosion
of about 3 mm.
[0116] In the GM9540P test, the maximum corrosion was mostly
between about 3.5-5 mm Average corrosion ranged between 3.69 and
1.88 mm. Formula 5A at 15 seconds had .ltoreq.3 mm of maximum
corrosion in all tested concentrations.
Corrosion Performance on HDG:
[0117] In APGE testing, most of the variations the average maximum
corrosion is approximately 4-7 mm. In most cases the paint
delamination was either drastically reduced or eliminated. In
GM9540P the maximum corrosion was mostly around 4 mm.
[0118] The foregoing test results showed that the alkaline
pre-rinses improved the corrosion performance of EG and HDG coated
with a zirconium-based pretreatment and painted as compared to the
same substrates coated and painted without the pre-rinse step. In
some instances corrosion performance of the pre-rinsed substrates
was comparable to zinc phosphate pretreatment and on average the
pre-rinsed substrates appear to meet the required automotive
manufacturer test specifications for corrosion resistance. The
alkaline pre-rinse did not negatively impact corrosion performance
for CRS. Formula 1A showed significant improvement at treatment
time of 30 seconds for CRS. During processing it was found that the
alkaline pre-rinse used cause increased metal etch on aluminum
substrates, and thus would be suitable for non-aluminum articles
and substrates.
[0119] The invention has been described in accordance with the
relevant legal standards, thus the description is exemplary rather
than limiting in nature. Variations and modifications to the
disclosed embodiment may become apparent to those skilled in the
art and do come within the scope of the invention. Accordingly, the
scope of legal protection afforded this invention can only be
determined by studying the following claims.
* * * * *