Method for cathodically treating an electrically conductive zinc surface

The disclosure relates to a process for forming a deposit on the surface of a metallic or conductive surface. The process employs an electrolytic process to deposit a mineral containing coating or film upon a metallic or conductive surface.

FIELD OF THE INVENTION 
The instant invention relates to a process for forming a deposit on the 
surface of a metallic or conductive surface. The process employs an 
electrolytic process to deposit a mineral containing coating or film upon 
a metallic or conductive surface. 
BACKGROUND OF THE INVENTION 
Silicates have been used in electrocleaning operations to clean steel, tin, 
among other surfaces. Electrocleaning is typically employed as a cleaning 
step prior to an electroplating operation. Using "Silicates As Cleaners In 
The Production of Tinplate" is described by L. J. Brown in February 1966 
edition of Plating. 
Processes for electrolytically forming a protective layer or film by using 
an anodic method are disclosed by U.S. Pat. No. 3,658,662 (Casson, Jr. et 
al.), and United Kingdom Patent No. 498,485; both of which are hereby 
incorporated by reference. 
U.S. Pat. No. 5,352,342 to Riffe, which issued on Oct. 4, 1994 and is 
entitled "Method And Apparatus For Preventing Corrosion Of Metal 
Structures" that describes using electromotive forces upon a zinc solvent 
containing paint. 
SUMMARY OF THE INVENTION 
The instant invention solves problems associated with conventional 
practices by providing a cathodic method for forming a protective layer 
upon a metallic substrate. The cathodic method is normally conducted by 
immersing a electrically conductive substrate into a silicate containing 
bath wherein a current is pased through the bath and the substrate is the 
cathode. A mineral layer comprising an amorphous matrix surrounding or 
incorporating metal silicate crystals forms upon the substrate. The 
mineral layer imparts improved corrosion resistance, among other 
properties, to the underlying substrate. 
The inventive process is also a marked improvement over conventional 
methods by obviating the need for solvents or solvent containing systems 
to form a corrosion resistant layer, i.e., a mineral layer. In contrast, 
to conventional methods he inventive process is substantially solvent 
free. By "substantially solvent free" it is meant that less than about 5 
wt. %, and normally less than about 1 wt. % volatile organic compounds 
(V.O.C.s) are present in the electrolytic environment. 
In contrast to conventional electrocleaning processes, the instant 
invention employs silicates in a cathodic process for forming a mineral 
layer upon the substrate. Conventional electrocleaning processes sought to 
avoid formation of oxide containing products such as greenalite whereas 
the instant invention relates to a method for forming silicate containing 
products, i.e., a mineral. 
CROSS REFERENCE TO RELATED PATENTS AND PATENT APPLICATIONS 
The subject matter of the instant invention is related to copending and 
commonly assigned Non-Provisional U.S. patent application Ser. Nos. 
08/850,323; 08/850,586; and 09/016,853 (EL001RH-6, EL001RH-7 and 
EL001RH-8) all currently pending, filed respectively on May 2, 1997 and 
even date herewith, and 08/791,337 U.S. Pat. No. 5,938,976, in the names 
of Robert L. Heimann et al., as a continuation in part of Ser. No. 
08/634,215 (filed on Apr. 18, 1996), now abandoned, in the names of Robert 
L. Heimann et al., and entitled "Corrosion Resistant Buffer System for 
Metal Products", which is a continuation in part of Non-Provisional U.S 
patent application Ser. No. 08/476,271 (filed on Jun. 7, 1995), now 
abandoned, in the names of Heimann et al., and corresponding to WIPO 
Patent Application Publication No. WO 96/12770, which in turn is a 
continuation in part of Non-Provisional U.S. patent application Ser. No. 
08/327,438 (filed on Oct. 21, 1994), now U.S. Pat. No. 5,714,093. 
The subject matter of this invention is related to Non-Provisional Patent 
Application Serial No. 09/016,849, currently pending, filed on even date 
herewith and entitled "Corrosion Protective Coatings". The subject matter 
of this invention is also related to Non-Provisional patent application 
Ser. No. 09/016,462, now U.S. Pat. No. 6,033,495 filed respectively, on 
even date herewith and Jan. 31, 1997 and entitled "Aqueous Gel 
Compositions and Use Thereof". The disclosure of the previously identified 
patents, patent applications and publications is hereby incorporated by 
reference.

DETAILED DESCRIPTION 
The instant invention relates to a process for depositing or forming a 
mineral containing coating or film upon a metallic or an electrically 
conductive surface. The process employs a mineral containing solution 
e.g., containing soluble mineral components, and utilizes an electrically 
enhanced method to obtain a mineral coating or film upon a metallic or 
conductive surface. By "mineral containing coating," it is meant to refer 
to a relatively thin coating or film which is formed upon a metal or 
conductive surface wherein at least a portion of the coating or film 
includes at least one of metal atom containing mineral, e.g., an amorphous 
phase or matrix surrounding or incorporating crystals comprising a zinc 
disilicate. Mineral and Mineral Containing are defined in the previously 
identified Copending and Commonly Assigned Patents and Patent 
Applications; incorporated by reference. By "electroyltic" or 
"electrodeposition" or "electrically enhanced", it is meant to refer to an 
environment created by passing an electrical current through a silicate 
containing medium while in contact with an electrically conductive 
substrate wherein the substrate functions as the cathode. 
The electroyltic environment can be established in any suitable manner 
including immersing the substrate, applying a silicate containing coating 
upon the substrate and thereafter applying an electrical current, among 
others. The preferred method for establishing the environment will be 
determined by the size of the substrate, electroplating time, among other 
parameters known in the electrodeposition art. 
The silicate containing medium can be a fluid bath, gel, spray, among other 
methods for contacting the substrate with the silicate medium. Examples of 
the silicate medium comprise a bath containing at least one alkali 
silicate, a gel comprising at least one alkali silicate and a thickener, 
among others. Normally, the medium comprises a bath of sodium silicate. 
The metal surface refers to a metal article as well as a non-metallic or an 
electrically conductive member having an adhered metal or conductive 
layer. Examples of suitable metal surfaces comprise at least one member 
selected from the group consisting of galvanized surfaces, zinc, iron, 
steel, brass, copper, nickel, tin, aluminum, lead, cadmium, magnesium, 
alloys thereof, among others. While the inventive process can be employed 
to coat a wide range of metal surfaces, e.g., copper, aluminum and ferrous 
metals, the mineral layer can be formed on a non-conductive substrate 
having at least one surface coated with an electrically conductive 
material, e.g., a ceramic material encapsulated within a metal. Conductive 
surfaces can also include carbon or graphite as well as conductive 
polymers (polyaniline for example). 
The mineral coating can enhance the surface characteristics of the metal or 
conductive surface such as resistance to corrosion, protect carbon (fibers 
for example) from oxidation and improve bonding strength in composite 
materials, and reduce the conductivity of conductive polymer surfaces 
including potential application in sandwich type materials. 
In an aspect of the invention, an electrogalvanized panel, e.g., a zinc 
surface, is coated electrolytically by being placed into an aqueous sodium 
silicate solution. After being placed into the silicate solution, a 
mineral coating or film containing silicates is deposited by using low 
voltage and low current. 
In one aspect of the invention, the metal surface, e.g., zinc, steel or 
lead, has been pretreated. By "pretreated" it is meant to refer to a batch 
or continuous process for conditioning the metal surface to clean it and 
condition the surface to facilitate acceptance of the mineral or silicate 
containing coating e.g., the inventive process can be employed as a step 
in a continuous process for producing corrosion resistant coil steel. The 
particular pretreatment will be a function of composition of the metal 
surface and desired composition of mineral containing coating/film to be 
formed on the surface. Examples of suitable pretreatments comprise at 
least one of cleaning, activating, and rinsing. A suitable pretreatment 
process for steel comprises: 
1) 2 minute immersion in a 3:1 dilution of Metal Prep 79 (Parker Amchem), 
2) two deionized rinses, 
3) 10 second immersion in a pH 14 sodium hydroxide solution, 
4) remove excess solution and allow to air dry, 
5) 5 minute immersion in a 50% hydrogen peroxide solution, 
6) remove excess solution and allow to air dry. 
In another aspect of the invention, the metal surface is pretreated by 
anodically cleaning the surface. Such cleaning can be accomplished by 
immersing the work piece or substrate into a medium comprising silicates, 
hydroxides, phosphates and carbonates. By using the work piece as the 
anode in a DC cell and maintaining a current of 100mA/cm.sup.2, this 
process can generate oxygen gas. The oxygen gas agitates the surface of 
the workpiece while oxidizing the substrate's surface. 
In a further aspect of the invention, the silicate solution is modified to 
include one or more dopant materials. While the cost and handling 
characteristics of sodium silicate are desirable, at least one member 
selected from the group of water soluble salts and oxides of tungsten, 
molybdenum, chromium, titanium, zircon, vanadium, phosphorus, aluminum, 
iron, boron, bismuth, gallium, tellurium, germanium, antimony, niobium 
(also known as columbium), magnesium and manganese, mixtures thereof, 
among others, and usually, salts and oxides of aluminum and iron can be 
employed along with or instead of a silicate. The dopant materials can be 
introduced to the metal or conductive surface in pretreatment steps prior 
to electrodeposition, in post treatment steps following electrodeposition, 
and/or by alternating electrolytic dips in solutions of dopants and 
solutions of silicates if the silicates will not form a stable solution 
with the water soluble dopants. When sodium silicate is employed as a 
mineral solution, desirable results can be achieved by using N grade 
sodium silicate supplied by Philadelphia Quartz (PQ) Corporation. The 
presence of dopants in the mineral solution can be employed to form 
tailored mineral containing surfaces upon the metal or conductive surface, 
e.g, an aqueous sodium silicate solution containing aluminate can be 
employed to form a layer comprising oxides of silicon and aluminum. 
The silicate solution can also be modified by adding water soluble 
polymers, and the elctrodeposition solution itself can be in the form of a 
flowable gel consistency. A suitable composition can be obtained in an 
aqueous composition comprising 3 wt % N-grade Sodium Silicate Solution (PQ 
Corp), 0.5 wt % Carbopol EZ-2 (BF Goodrich), about 5 to 10 wt. % fumed 
silica, mixtures thereof, among others . Further, the aqueous silicate 
solution can be filled with a water dispersible polymer such as 
polyurethane to electro deposit a mineral-polymer composite coating. The 
characteristics of the electrodeposition solution can be modified or 
tailored by using an anode material as a source of ions which can be 
available for codeposition with the mineral anions and/or one or more 
dopants. The dopants can be useful for building additional thickness of 
the electrodeposited mineral layer. 
The following sets forth the parameters which may be employed for tailoring 
the inventive process to obtain a desirable mineral containing coating: 
1. Voltage 
2. Current Density 
3. Apparatus or Cell Design 
4. Deposition Time 
5. Concentration of the N-grade sodium silicate solution 
7. Type and concentration of anions in solution 
8. Type and concentration of cations in solution 
9. Composition of the anode 
10. Composition of the cathode 
11. Temperature 
12. Pressure 
13. Type and Concentration of Surface Active Agents 
The specific ranges of the parameters above depend on the substrate to be 
deposited on and the intended composition to be deposited. Items 1, 2, 7, 
and 8 can be especially effective in tailoring the chemical and physical 
characteristics of the coating. That is, items 1 and 2 can affect the 
deposition time and coating thickness whereas items 7 and 8 can be 
employed for introducing dopants that impart desirable chemical 
characteristics to the coating. The differing types of anions and cations 
can comprise at least one member selected from the group consisting of 
Group I metals, Group II metals, transition and rare earth metal oxides, 
oxyanions such as mineral, molybdate, phosphate, titanate, boron nitride, 
silicon carbide, aluminum nitride, silicon nitride, mixtures thereof, 
among others. 
While the above description places particular emphasis upon forming a 
mineral containing layer upon a metal surface, the inventive process can 
be combined with or replace conventional metal finishing practices. The 
inventive mineral layer can be employed to protect a metal finish from 
corrosion thereby replacing conventional phosphating process, e.g., in the 
case of automotive metal finishing the inventive process could be utilized 
instead of phosphates and chromates and prior to coating application e.g., 
E-Coat. Further, the aforementioned aqueous mineral solution can be 
replaced with an aqueous polyurethane based solution containing soluble 
silicates and employed as a replacement for the so-called automotive 
E-coating and/or powder painting process. Moreover, depending upon the 
dopants and concentration thereof present in the mineral deposition 
solution, the inventive process can produce microelectronic films, e.g., 
on metal or conductive surfaces in order to impart enhanced electrical and 
corrosion resistance, or to resist ultraviolet light and monotomic oxygen 
containing environments such as space. 
The inventive process can be employed in a virtually unlimited array of 
end-uses such as in conventional plating operations as well as being 
adaptable to field service. For example, the inventive mineral containing 
coating can be employed to fabricate corrosion resistant metal products 
that conventionally utilize zinc as a protective coating, e.g., automotive 
bodies and components, grain silos, bridges, among many other end-uses. 
The x-ray photoelectron spectroscopy (ESCA) data in the following Examples 
demonstrate the presence of a unique metal disilicate species within the 
mineralized layer, e.g., ESCA measures the binding energy of the 
photoelectrons of the atoms present to determine bonding characteristics. 
The following Examples are provided to illustrate certain aspects of the 
invention and it is understood that such an Example does not limit the 
scope of the invention as defined in the appended claims. 
EXAMPLE 1 
The following apparatus and materials were employed in this Example: 
Standard Electrogalvanized Test Panels, ACT Laboratories 
10% (by weight) N-grade Sodium Mineral solution 
12 Volt EverReady.RTM. battery 
1.5 Volt Ray-O-Vac.RTM. Heavy Duty Dry Cell Battery 
Triplett RMS Digital Multimeter 
30 .mu.F Capacitor 
29.8 k.OMEGA. Resistor 
A schematic of the circuit and apparatus which were employed for practicing 
the Example are illustrated in FIG. 1. Referring now to FIG. 1, the 
aforementioned test panels were contacted with a solution comprising 10% 
sodium mineral and deionized water. A current was passed through the 
circuit and solution in the manner illustrated in FIG. 1. The test panels 
was exposed for 74 hours under ambient environmental conditions. A visual 
inspection of the panels indicated that a light-grey colored coating or 
film was deposited upon the test panel. 
In order to ascertain the corrosion protection afforded by the mineral 
containing coating, the coated panels were tested in accordance with ASTM 
Procedure No. B117. A section of the panels was covered with tape so that 
only the coated area was exposed and, thereafter, the taped panels were 
placed into salt spray. For purposes of comparison, the following panels 
were also tested in accordance with ASTM Procedure No. B 117, 1) Bare 
Electrogalvanized Panel, and 2) Bare Electrogalvanized Panel soaked for 70 
hours in a 10% Sodium Mineral Solution. In addition, bare zinc phosphate 
coated steel panels(ACT B952, no Parcolene) and bare iron phosphate coated 
steel panels (B1000, no Parcolene) were subjected to salt spray for 
reference. 
The results of the ASTM Procedure are listed in the Table below: 
______________________________________ 
Panel Description Hours in B117 Salt Spray 
______________________________________ 
Zinc phosphate coated steel 
1 
Iron phosphate coated steel 
1 
Standard Bare Electrogalvanize Panel 
.apprxeq.120 
Standard Panel with Sodium Mineral 
.apprxeq.120 
Soak 
Coated Cathode of the Invention 
240+ 
______________________________________ 
The above Table illustrates that the instant invention forms a coating or 
film which imparts markedly improved corrosion resistance. It is also 
apparent that the process has resulted in a corrosion protective film that 
lengthens the life of electrogalvanized metal substrates and surfaces. 
ESCA analysis was performed on the zinc surface in accordance with 
conventional techniques and under the following conditions: 
Analytical conditions for ESCA: 
______________________________________ 
Instrument Physical Electronics Model 5701 LSci 
X-ray source Monochromatic aluminum 
Source power 350 watts 
Analysis region 
2 mm .times. 0.8 mm 
Exit angle* 50.degree. 
Electron acceptance angle 
.+-.7.degree. 
Charge neutralization 
electron flood gun 
Charge correction 
C--(C,H) in C 1s spectra at 284.6 eV 
______________________________________ 
*Exit angle is defined as the angle between the sample plane and the 
electron analyzer lens. 
The silicon photoelectron binding energy was used to characterized the 
nature of the formed species within the mineralized layer that was formed 
on the cathode. This species was identified as a zinc disilicate modified 
by the presence of sodium ion by the binding energy of 102.1 eV for the 
Si(2p) photoelectron. 
EXAMPLE 2 
This Example illustrates performing the inventive electrodeposition process 
at an increased voltage and current in comparison to Example 1. 
Prior to the electrodeposition, the cathode panel was subjected to 
preconditioning process: 
1) 2 minute immersion in a 3:1 dilution of Metal Prep 79 (Parker Amchem), 
2) two deionized rinse, 
3) 10 second immersion in a pH 14 sodium hydroxide solution, 
4) remove excess solution and allow to air dry, 
5) 5 minute immersion in a 50% hydrogen peroxide solution, 
6) Blot to remove excess solution and allow to air dry. 
A power supply was connected to an electrodeposition cell consisting of a 
plastic cup containing two standard ACT cold roll steel (clean, 
unpolished) test panels. One end of the test panel was immersed in a 
solution consisting of 10% N grade sodium mineral (PQ Corp.) in deionized 
water. The immersed area (1 side) of each panel was approximately 3 inches 
by 4 inches (12 sq. in.) for a 1:1 anode to cathode ratio. The panels were 
connected directly to the DC power supply and a voltage of 6 volts was 
applied for 1 hour. The resulting current ranged from approximately 
0.7-1.9 Amperes. The resultant current density ranged from 0.05-0.16 
amps/in.sup.2. 
After the electrolytic process, the coated panel was allowed to dry at 
ambient conditions and then evaluated for humidity resistance in 
accordance with ASTM Test No. D2247 by visually monitoring the corrosion 
activity until development of red corrosion upon 5% of the panel surface 
area. The coated test panels lasted 25 hours until the first appearance of 
red corrosion and 120 hours until 5% red corrosion. In comparison, 
conventional iron and zinc phosphated steel panels develop first corrosion 
and 5% red corrosion after 7 hours in ASTM D2247 humidity exposure. The 
above Examples, therefore, illustrate that the inventive process offers an 
improvement in corrosion resistance over iron and zinc phosphated steel 
panels. 
EXAMPLE 3 
Two lead panels were prepared from commercial lead sheathing and cleaned in 
6M HCl for 25 minutes. The cleaned lead panels were subsequently placed in 
a solution comprising 1 wt. % N-grade sodium silicate (supplied by PQ 
Corporation). 
One lead panel was connected to a DC power supply as the anode and the 
other was a cathode. A potentional of 20 volts was applied initially to 
produce a current ranging from 0.9 to 1.3 Amperes. After approximately 75 
minutes the panels were removed from the sodium silicate solution and 
rinsed with deionized water. 
ESCA analysis was performed on the lead surface. The silicon photoelectron 
binding energy was used to characterized the nature of the formed species 
within the mineralized layer. This species was identified as a lead 
disilicate modified by the presence of sodium ion by the binding energy of 
102.0 eV for the Si(2p) photoelectron. 
EXAMPLE 4 
This Example demonstrates forming a mineral surface upon an aluminum 
substrate. Using the same apparatus in Example 1, aluminum coupons 
(3".times.6") were reacted to form the metal silicate surface. Two 
different alloys of aluminum were used, Al 2024 and Al 7075. Prior to the 
panels being subjected to the electrolytic process, each panel was 
prepared using the methods outlined below in Table A. Each panel was 
washed with reagent alcohol to remove any excessive dirt and oils. The 
panels were either cleaned with Alumiprep 33, subjected to anodic cleaning 
or both. Both forms of cleaning are designed to remove excess aluminum 
oxides. Anodic cleaning was accomplished by placing the working panel as 
an anode into an aqueous solution containing 5% NaOH, 2.4% Na.sub.2 
CO.sub.3, 2% Na.sub.2 SiO.sub.3, 0.6% Na.sub.3 PO.sub.4, and applying a 
potential to maintain a current density of 100mA/cm.sup.2 across the 
immersed area of the panel for one minute. 
Once the panel was cleaned, it was placed in a liter beaker filled with 800 
mL of solution. The baths were prepared using deionized water and the 
contents are shown in the table below. The panel was attached to the 
negative lead of a DC power supply by a wire while another panel was 
attached to the positive lead. The two panels were spaced 2 inches apart 
from each other. The potential was set to the voltage shown on the table 
and the cell was run for one hour. 
TABLE A 
__________________________________________________________________________ 
Example 
A B C D E F G H 
__________________________________________________________________________ 
Alloy type 
2024 
2024 
2024 
2024 
7075 
7075 
7075 
7075 
Anodic Yes Yes No No Yes Yes No No 
Cleaning 
Acid Wash 
Yes Yes Yes Yes Yes Yes Yes Yes 
Bath Solution 
Na.sub.2 SiO.sub.3 
1% 
10% 
1% 
10% 
1% 
10% 
1% 
10% 
H.sub.2 O.sub.2 
1% 
0% 
0% 
1% 
1% 
0% 
0% 
Potential 
12 V 
18 V 
12 V 
18 V 
12 V 
18 V 
12 V 
18 V 
__________________________________________________________________________ 
ESCA was used to analyze the surface of each of the substrates. Every 
sample measured showed a mixture of silica and metal silicate. Without 
wishing to be bound by any theory or explanation, it is believed that the 
metal silicate is a result of the reaction between the metal cations of 
the surface and the alkali silicates of the coating. It is also believed 
that the silica is a result of either excess silicates from the reaction 
or precipitated silica from the coating removal process. The metal 
silicate is indicated by a Si (2p) binding energy (BE) in the low 102 eV 
range, typically between 102.1 to 102.3. The silica can be seen by Si(2p) 
BE between 103.3 to 103.6 eV. The resulting spectra show overlapping 
peaks, upon deconvolution reveal binding energies in the ranges 
representative of metal silicate and silica. 
EXAMPLE 5 
This Example illustrates an alternative to immersion for creating the 
silicate containing medium. 
An aqueous gel made from 5% sodium silicate and 10% fumed silica was used 
to coat cold rolled steel panels. One panel was washed with reagent 
alcohol, while the other panel was washed in a phosphoric acid based metal 
prep, followed by a sodium hydroxide wash and a hydrogen peroxide bath. 
The apparatus was set up using a DC power supply connecting the positive 
lead to the steel panel and the negative lead to a platinum wire wrapped 
with glass wool. This setup was designed to simulate a brush plating 
operation. The "brush" was immersed in the gel solution to allow for 
complete saturation. The potential was set for 12V and the gel was painted 
onto the panel with the brush. As the brush passed over the surface of the 
panel, hydrogen gas evolution could be seen. The gel was brushed on for 
five minutes and the panel was then washed with DI water to remove any 
excess gel and unreacted silicates. 
ESCA was used to analyze the surface of each steel panel. ESCA detects the 
reaction products between the metal substrate and the environment created 
by the electrolytic process. Every sample measured showed a mixture of 
silica and metal silicate. The metal silicate is a result of the reaction 
between the metal cations of the surface and the alkali silicates of the 
coating. The silica is a result of either excess silicates from the 
reaction or precipitated silica from the coating removal process. The 
metal silicate is indicated by a Si (2p) binding energy (BE) in the low 
102 eV range, typically between 102.1 to 102.3. The silica can be seen by 
Si(2p) BE between 103.3 to 103.6 eV. The resulting spectra show 
overlapping peaks, upon deconvolution reveal binding energies in the 
ranges representative of metal silicate and silica. 
EXAMPLE 6 
Using the same apparatus in Example 1, cold rolled steel coupons (ACT 
laboratories) were reacted to form the metal silicate surface. Prior to 
the panels being subjected to the electrolytic process, each panel was 
prepared using the methods outlined below in Table B. Each panel was 
washed with reagent alcohol to remove any excessive dirt and oils. The 
panels were either cleaned with Metalprep 79 (Parker Amchem), subjected to 
anodic cleaning or both. Both forms of cleaning are designed to remove 
excess metal oxides. Anodic cleaning was accomplished by placing the 
working panel as an anode into an aqueous solution containing 5% NaOH, 
2.4% Na.sub.2 CO.sub.3, 2% Na.sub.2 SiO.sub.3, 0.6% Na.sub.3 PO.sub.4, and 
applying a potential to maintain a current density of 100mA/cm.sup.2 
across the immersed area of the panel for one minute. 
Once the panel was cleaned, it was placed in a 1 liter beaker filled with 
800 mL of solution. The baths were prepared using deionized water and the 
contents are shown in the table below. The panel was attached to the 
negative lead of a DC power supply by a wire while another panel was 
attached to the positive lead. The two panels were spaced 2 inches apart 
from each other. The potential was set to the voltage shown on the table 
and the cell was run for one hour. 
TABLE B 
______________________________________ 
Example AA BB CC DD EE 
______________________________________ 
Substrate type 
CRS CRS CRS CRS.sup.1 
CRS.sup.2 
Anodic Cleaning 
No Yes No No No 
Acid Wash Yes Yes Yes No No 
Bath Solution 
Na.sub.2 SiO.sub.3 
1% 10% 1% -- -- 
Potential (V) 
14-24 6 (CV) 12 V -- -- 
(CV) 
Current Density 
23 (CC) 23-10 85-48 -- -- 
(mA/cm.sup.2) 
B177 2 hrs 1 hr 1 hr 0.25 hr 
0.25 hr 
______________________________________ 
.sup.1 Cold Rolled Steel Control No treatment was done to this panel. 
.sup.2 Cold Rolled Steel with iron phosphate treatment (ACT Laboratories) 
No further treatments were performed 
The electrolytic process was either run as a constant current or constant 
voltage experiment, designated by the CV or CC symbol in the table. 
Constant Voltage experiments applied a constant potential to the cell 
allowing the current to fluctuate while Constant Current experiments held 
the current by adjusting the potential. Panels were tested for corrosion 
protection using ASTM B117. Failures were determined at 5% surface 
coverage of red rust. 
ESCA was used to analyze the surface of each of the substrates. ESCA 
detects the reaction products between the metal substrate and the 
environment created by the electrolytic process. Every sample measured 
showed a mixture of silica and metal silicate. The metal silicate is a 
result of the reaction between the metal cations of the surface and the 
alkali silicates of the coating. The silica is a result of either excess 
silicates from the reaction or precipitated silica from the coating 
removal process. The metal silicate is indicated by a Si (2p) binding 
energy (BE) in the low 102 eV range, typically between 102.1 to 102.3. The 
silica can be seen by Si(2p) BE between 103.3 to 103.6 eV. The resulting 
spectra show overlapping peaks, upon deconvolution reveal binding energies 
in the ranges representative of metal silicate and silica. 
EXAMPLE 7 
Using the same apparatus in Example 1, zinc galvanized steel coupons (EZG 
60G ACT Laboratories) were reacted to form the metal silicate surface. 
Prior to the panels being subjected to the electrolytic process, each 
panel was prepared using the methods outlined below in Table C. Each panel 
was washed with reagent alcohol to remove any excessive dirt and oils. 
Once the panel was cleaned, it was placed in a 1 liter beaker filled with 
800 mL of solution. The baths were prepared using deionized water and the 
contents are shown in the table below. The panel was attached to the 
negative lead of a DC power supply by a wire while another panel was 
attached to the positive lead. The two panels were spaced approximately 2 
inches apart from each other. The potential was set to the voltage shown 
on the table and the cell was run for one hour. 
TABLE C 
______________________________________ 
Example A1 B2 C3 D5 
______________________________________ 
Substrate type 
GS GS GS GS.sup.1 
Bath Solution 
10% 1% 10% -- 
Na.sub.2 SiO.sub.3 
Potential (V) 
6 (CV) 10 (CV) 18 (CV) 
-- 
Current Density 
22-3 7-3 142-3 -- 
(mA/cm.sup.2) 
B177 336 hrs 224 hrs 216 hrs 
96 hrs 
______________________________________ 
.sup.1 Galvanized Steel Control No treatment was done to this panel. 
Panels were tested for corrosion protection using ASTM B117. Failures were 
determined at 5% surface coverage of red rust. 
ESCA was used to analyze the surface of each of the substrates. ESCA 
detects the reaction products between the metal substrate and the 
environment created by the electrolytic process. Every sample measured 
showed a mixture of silica and metal silicate. The metal silicate is a 
result of the reaction between the metal cations of the surface and the 
alkali silicates of the coating. The silica is a result of either excess 
silicates from the reaction or precipitated silica from the coating 
removal process. The metal silicate is indicated by a Si (2p) binding 
energy (BE) in the low 102 eV range, typically between 102.1 to 102.3. The 
silica can be seen by Si(2p) BE between 103.3 to 103.6 eV. The resulting 
spectra show overlapping peaks, upon deconvolution reveal binding energies 
in the ranges representative of metal silicate and silica. 
EXAMPLE 8 
Using the same apparatus in Example 1, copper coupons (C110 Hard, Fullerton 
Metals) were reacted to form the metal silicate surface. Prior to the 
panels being subjected to the electrolytic process, each panel was 
prepared using the methods outlined below in Table D. Each panel was 
washed with reagent alcohol to remove any excessive dirt and oils. 
Once the panel was cleaned, it was placed in a 1 liter beaker filled with 
800 mL of solution. The baths were prepared using deionized water and the 
contents are shown in the table below. The panel was attached to the 
negative lead of a DC power supply by a wire while another panel was 
attached to the positive lead. The two panels were spaced 2 inches apart 
from each other. The potential was set to the voltage shown on the table 
and the cell was run for one hour. 
TABLE D 
______________________________________ 
Example AA1 BB2 CC3 DD4 EE5 
______________________________________ 
Substrate type 
Cu Cu Cu Cu Cu.sup.1 
Bath Solution 
10% 10% 1% 1% -- 
Na.sub.2 SiO.sub.3 
Potential (V) 
12 (CV) 6 (CV) 6 (CV) 36 (CV) 
-- 
Current Density 
40-17 19-9 4-1 36-10 -- 
(mA/cm.sup.2) 
B117 11 hrs 11 hrs 5 hrs 5 hrs 2 hrs 
______________________________________ 
.sup.1 Copper Control No treatment was done to this panel. 
Panels were tested for corrosion protection using ASTM B117. Failures were 
determined by the presence of copper oxide which was indicated by the 
appearance of a dull haze over the surface. 
ESCA was used to analyze the surface of each of the substrates. ESCA allows 
us to examine the reaction products between the metal substrate and the 
environment set up from the electrolytic process. Every sample measured 
showed a mixture of silica and metal silicate. The metal silicate is a 
result of the reaction between the metal cations of the surface and the 
alkali silicates of the coating. The silica is a result of either excess 
silicates from the reaction or precipitated silica from the coating 
removal process. The metal silicate is indicated by a Si (2p) binding 
energy (BE) in the low 102 eV range, typically between 102.1 to 102.3. The 
silica can be seen by Si(2p) BE between 103.3 to 103.6 eV. The resulting 
spectra show overlapping peaks, upon deconvolution reveal binding energies 
in the ranges representative of metal silicate and silica.