MXPA99006963A - An electrolytic process for forming a mineral containing coating - Google Patents

Abstract

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.

Description

ELECTROLYTIC PROCESS TO FORM A COATING CONTAINING MINERAL FIELD OF THE INVENTION The present 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 coating or film containing mineral on a metallic or conductive surface.

BACKGROUND OF THE INVENTION Silicates have been used in electrodeposition operations to clean steel surfaces, tin, among others. The electrodeposition is typically employed as a cleaning step before an electrodeposition operation. The use of "Silicates as Cleaners in the Production of Tin Plates" is described by L. J. Bro n in February 1996 in the 1966 edition of Plating. The processes for electrolytically forming a protective layer or film using an anode method are described by U.S. Patent No. 3,658,662 (Casson, Jr. et al.), And British Patent No. 498,485; both of which are incorporated herein by reference.

REF .: 30761 U.S. Patent No. 5,352,342 to Riffe, which was granted on October 4, 1994 and is entitled "Method and Apparatus for Preventing Corrosion of Metallic Structures" which describes using electromotive forces on a paint containing zinc solvent .

BRIEF DESCRIPTION OF THE INVENTION The present invention solves the problems associated with conventional practices by providing a cathode method for forming a protective layer on a metal film. The cathode method is usually conducted by immersing an electrically conductive substrate in a silicate-containing bath, where a current is passed through the bath and the substrate is the cathode. A layer of ore comprising an amorphous matrix surrounding or incorporating metal silicate crystals is formed on the substrate. The mineral layer imparts enhanced corrosion resistance, among other properties to the underlying substrate. The process of the invention is also a remarkable improvement over conventional methods by obviating the need for solvents or systems containing solvent to form a corrosion resistant layer, i.e., a mineral layer. In contrast, with conventional methods the process of the invention is substantially solvent-free. "Substantially solvent-free" means that less than about 5% by weight, and usually less than about 1% by weight, of volatile organic compounds (V.O.C.) in the electrolytic environment is present. In contrast to conventional electrodeposition processes, the present invention employs silicates in a cathodic process to form a mineral layer on the substrate. Conventional electrodeposition processes seek to avoid the formation of oxide-containing products such as greenalite, while the present invention relates to a method for forming silicate-containing products, ie, a mineral.

CROSS REFERENCE WITH PATENTS AND PATENT APPLICATIONS RELATED The subject matter of the present invention relates to US Patent Applications Serial Nos. 08 / 850,323; 08 / 850,586; and 09 / 016,853 (corresponding to PCT Publication No. PCT / US98 / 01772) co-pending and commonly assigned, Non-Provisional, and 08 / 791,337, in the name of Robert L. Heimann et al., as a continuation in part of the Serial No. 08 / 634,215 in the name of Robert L. Heimann et al. , and entitled "Corrosion Resistant Corrosion System for Metal Products", which is a continuation in part of the United States Patent Application No. Provisional Serial No. 08 / 476,271 in the name of Robert L. Heimann et al., and which corresponds to PCT Publication No. WO 96/12770, which in turn is a continuation in part of US Patent Application No. Provisional Serial No. 08 / 327,438, now US Patent No. 5, 714.093. The subject matter of this invention is related to the Non-Provisional Patent Application Serial No. 09 / 016,849 (corresponding to PCT Publication No. PCT / US98 / 01777), entitled "Corrosion Protective Coatings". The subject matter of this invention is also related to the Non-Provisional Patent Application Serial No. 09 / 016,462, entitled "Aqueous Gel Compositions and Use thereof". The descriptions of the patents, patent applications and publications identified above are hereby incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a schematic drawing of the circuit and apparatus that can be used to practice an aspect of the invention.

DETAILED DESCRIPTION The present invention relates to a process for depositing a coating or film containing a mineral on a metallic or electrically conductive surface. The process employs a solution containing a mineral, for example, which contains soluble mineral components, and uses an electrically improved method to obtain a mineral coating or film on a metallic or conductive surface. "Mineral-containing coating" refers to a relatively thin coating or film that is formed on a metal or conductive surface where at least a portion of the coating or film includes at least one metal atom containing mineral, eg, a amorphous phase or matrix surrounding or incorporating crystals comprising a zinc disilicate. Mineral and Mineral Content are defined in the Commonly Assigned and Co-pending Patent Applications and Patents identified above; incorporated as reference. "Electrolyte" or "electrodeposition" or "electrically enhanced" refers to an environment created by passing an electric current through a silicate-containing medium while in contact with an electrically conductive substrate, where the substrate functions as the cathode. The electrolytic environment can be established in any suitable manner including by submerging the substrate, applying a coating containing silicate on the substrate and subsequently applying an electric current, 3 among others. The preferred method for establishing the environment will be determined by the size of the substrate, the electrodeposition time, among other parameters known in the electrodeposition technique. 5 The medium containing silicate can be a bath 'fluid, gel, spray, among other methods to flush the substrate with the silicate medium. The examples of silicate medium comprise a bath containing at least "; an alkaline silicate, a gel comprising a silicate 10 alkaline 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 electrical member Driver who has a metal or conductive cap attached. Examples of suitable metal surfaces comprise at least one member selected from the group consisting of galvanized surfaces, zinc, iron, steel, bronze, copper, nickel, tin, aluminum, lead, cadmium, magnesium, alloys thereof, among others . Although the process of the invention . * - '20 can be used to coat a wide range of metal surfaces, for example, copper, aluminum and ferrous metals, the mineral layer can be formed on a non-conductive substrate having at least one surface c * T coated with a electrically conductive material, by f * - 25 example, a ceramic material encapsulated within a metal. The conductive surfaces can also include carbon or graphite as well as conductive polymers (polyaniline for example). The mineral coating can improve the characteristics of the metal surface or conductive such as corrosion resistance, protection of carbon (fibers for example) against oxidation and improve the adhesive strength in composite materials, and reduce the conductivity of the surfaces conducting polymers, including the application of potential in sandwich-type materials. In one aspect of the invention, an electrogalvanized panel, for example, a zinc surface, is electrolytically coated by placing it in an aqueous solution of sodium silicate. After being placed in the silicate solution, a mineral coating or film containing silicates is deposited using a low voltage and a low current. In an aspect of the invention, the metal surface, for example, zinc, steel or lead, has been pretreated. "Pretreated" refers 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, for example, the process of the invention can be employed as a step in a continuous process to produce corroded steel resistant to corrosion. The particular pretreatment will be a function of the composition of the metal surface and the desired composition of the coating / film containing mineral to be formed on the surface. Examples of suitable pretreatments comprise at least one of cleaning, activating and rinsing. A pretreatment process suitable for cleaning includes: 1) immersion for 2 minutes in a 3: 1 dilution of Metal Prep 79 (Parker Amchem), 2) two deionized rinses, 3) immersion for 10 seconds in a sodium hydroxide solution at pH 14, 4) remove the excess solution and allow to air dry, 5) immersion for 5 minutes in a 50% hydrogen peroxide solution, 6) remove the 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 effected by immersing the workpiece or substrate in a medium comprising silicates, hydroxides, phosphates and carbonates. Using the workpiece as the anode in a CD (Direct Current) cell and maintaining a current of 100mA / cm2, this process can generate oxygen gas. The oxygen gas agitates the surface of the workpiece while oxidizing the surface of the substrate. In a further aspect of the invention, the silicate solution is modified to include one or more contaminating materials. Although 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, zirconium, vanadium, phosphorus, aluminum, iron, boron, bismuth, gallium, tellurium, germanium, antimony, niobium (also known as columbium), magnesium and manganese; mixtures thereof, among others, and usually, aluminum and iron salts and oxides may be employed together with or in place of the silicate. The Polluting or adulterating materials can be introduced into the metallic or conductive surface in pretreatment steps before electrodeposition, in subsequent treatment steps after electrodeposition, and / or by alternating electrolytic immersions in solutions of adulterants and silicate solutions if the silicates will not form a stable solution with the water-soluble adulterants. When sodium silicate is used as a mineral solution, desirable results can be expected using sodium grade L silicate distributed by Philadelphia Quartz (PQ) Corporation. The presence of adulterants in the mineral solution can be used to form designed surfaces containing mineral on the metallic or conductive surface, for example, an aqueous solution of sodium silicate containing aluminate can be used to form a layer comprising silica and aluminum oxides . The silicate solution can also be modified by adding water-soluble polymers and in the electrodeposition solution itself it can be in the form of a fluid gel consistency. A suitable composition can be obtained in an aqueous composition comprising 3% by weight of N-grade Sodium Silicate Solution (PQ Corp), 0.5% by weight of Carbopol EZ-2 (BF Goodrich), approximately 5 to 10% by weight of fuming silica, mixtures thereof, among others. In addition, the aqueous silicate solution can be filled with a water dispersible polymer such as polyurethane to electrodeposit a mineral-polymer composite coating. The characteristics of the electrodeposition solution can be modified or designed using an anionic material as a source of ions that may be available for co-localization with mineral anions and / or one or more adulterants. The adulterants can be useful to create an additional thickness of the electrodeposited mineral layer.

The following are the parameters that can be used to design the process of the invention to obtain a coating that contains desirable mineral: I. Voltage 2. Current Density 3. Apparatus Design or Cell 4. Deposition Time 5. Concentration of the sodium silicate solution grade N 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 II. Temperature 12. Pressure 13. Type and Concentration of Agents with Surface Activity The specific intervals of the above parameters depend on the substrate to be deposited and the composition that is to be deposited. Points 1, 2, 7 and 8 can be especially effective in designing the chemical and physical characteristics of the coating. That is, the points 1 and 2 can affect the deposition time and the thickness of the coating while the points 7 and 8 can be used to introduce adulterants that impart desirable chemical characteristics to the coating. The different types of anions and cations may comprise at least one member selected from the group consisting of Group I metals, Group II metals, transition metal oxides and rare earths, oxyanions such as minerals, molybdate, phosphate, titanate. , boron nitride, silicon carbide, aluminum nitride, silicon nitride, mixtures thereof, among others. Although the foregoing description places particular emphasis on the formation of a mineral-containing layer on a metal surface, the process of the invention can be combined or replaced with conventional metal finishing practices. The mineral layer of the invention can be used to protect a metallic finish against corrosion, thus replacing the conventional phosphating process, for example, in the case of the automotive metal finish the process of the invention could be used in place of the phosphates and chromates before the application of the coating for example, coating E. In addition, The aforementioned aqueous mineral solution can be replaced with an aqueous solution based on polyurethane containing soluble silicates and used as a replacement for the so-called automotive E coating and / or powder painting process.

In addition, depending on the adulterants and concentration thereof present in the mineral deposition solution, the process of the invention can produce microelectronic films, for example, on metal or conductive surfaces to impart greater electrical or corrosion resistance, or to resist ultraviolet light and environments that contain monatomic oxygen such as in space. The process of the invention can be employed in a virtually unlimited array of end uses such as in conventional coating operations as well as being adapted to field service. For example, the mineral-containing coating of the invention can be used to make corrosion-resistant metal products that conventionally use zinc as a protective coating, for example, automotive bodies and components, grain silos, bridges, among many other uses. final. The X-ray photoelectron spectroscopy (ESCA) data in the following Examples demonstrate the presence of a single spice of metal disilicates within the mineralized layer, for example, the ESCA measures the binding energy of the photoelectrons of the atoms present to determine the binding characteristics. The following Examples are provided to illustrate certain aspects of the invention and it should be understood that such Examples do not limit the scope of the invention as defined in the appended claims.

EXAMPLE 1 The following equipment and materials were used in this Example: Standard Electro-Galvanized Test Panels, ACT Laboratories 10% N-grade Sodium Ore Solution (by weight) 12-Volt EverReady Battery High-Duration Dry Cell, Ray-O-Vac 1.5 Volts Digital Multimeter Triplet RMS Capacitor 30 μF Resistance of 29.8 kO A schematic of the circuit and apparatus that were used to practice the Example are illustrated in Figure 1. Referring now to Figure 1, the test panels mentioned above were placed in contact with a solution comprising 10% sodium mineral and deionized water. A current was passed through the circuit and the solution in the manner illustrated in Figure 1. The test panels were exposed for 74 hours under ambient conditions. A visual inspection of the panels indicated that a mixed color coating or film was deposited on the test panel. To determine the corrosion protection provided 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, subsequently, the protected panels were placed in a salt spray. For comparison purposes, the following panels were also tested in accordance with ASTM Procedure No. B117, 1) Uncoated Electro-Galvanized Panel, and 2) Uncoated Electro-Galvanized Panel submerged for 70 hours in a 10% Sodium Ore Solution . In addition, uncoated zinc phosphate coated steel panels (ACT B952, not Parcolene) and uncoated iron phosphate coated panels (B1000, not Parcolene) were subjected to salt spray as a reference. The results of the ASTM Procedure are listed in the following Table: The above Table illustrates that the present invention forms a coating or film which imparts markedly improved corrosion resistance. It is also evident that the process has resulted in a corrosion protective film that extends the life of substrates and electrogalvanized metal surfaces. The ESCA analysis was carried out on the zinc surface according to conventional techniques and under the following conditions: Analytical conditions for the ESCA: Instrument Physical Electronics Model 57011 LSci Source of X-rays Aluminum monochromatic Power source 350 watts Analysis region 2 mm X 0.8 mm Output angle * 50 ° Electron acceptance angle + 7 ° Load neutralization Electron flow cannon Load correction C- (CH) in the spectrum C Is a 284.6 eV * The exit angle is defined as the angle between the plane of the sample and the electron analyzer lenses. The photoelectronic binding energy of silicon was used to characterize the nature of the species formed within the mineralized layer that formed on the cathode. The species were identified as zinc disilicate modified by the presence of sodium ion by the binding energy of 102.1 eV for the photoelectron Si (2p).

EXAMPLE 2 This example illustrates the operation of the electrodeposition process of the invention at a greater assembly and stream in composition with Example 1. Prior to electrodeposition, the cathode panel was subjected to the preconditioning process: 1) 2 minute immersion in a 3: 1 dilution of Metal Prep 79 (Parker A chem), 2) two deionized rinses, 3) immersion for 10 seconds in a sodium hydroxide solution at pH 14, 4) removal of excess solution and air drying , 5) immersion for 5 minutes in a 50% hydrogen peroxide solution, 6) stain to remove excess solution and allow to air dry. A power source was connected to an electrodeposition cell consisting of a plastic container containing two test panels of standard ACT cold rolled steel (clean, not polished). One end of the test panel was immersed in a solution consisting of 10% N grade sodium ore (PQ Corp.) in deionized water. The submerged area (side 1) of each panel was approximately 7.62 centimeters by 10.16 centimeters (3 inches by 4 inches) (77.41 square centimeters (12 square inches)) for an anode to cathode ratio of 1: 1. The panels were connected directly to the DC power supply (Direct Current) and a voltage of 6 Volts was applied for 1 hour. The resulting current fluctuates from about 0.7-1.9 Amperes. The resulting current density fluctuates from 0.0077-0.0248 amps / cm2 (0.05-0.16 amps / in2). After the electrolytic process, the coated panel was allowed to dry at ambient conditions and then evaluated for moisture resistance according to ASTM Test No. D2247 visually verifying the corrosion until the development of red corrosion on 5% of the area surface of the panel. The coated test panel was left for 25 hours until red corrosion first appeared and 120 hours to 5% red corrosion. In comparison, the steel panel with conventional zinc and iron phosphate, developed for the first time corrosion and 5% red corrosion after 7 hours on exposure to moisture ASTM D2247. The above Examples thus illustrate that the process of the invention offers an improvement in corrosion resistance on steel panels with iron and zinc phosphate.

EXAMPLE 3 Two lead panels of commercial lead liner were prepared and cleaned in 6M HCl for 25 minutes.

The clean lead panels were subsequently placed in a solution comprising 1% by weight of sodium silicate grade N (distributed by PQ Corporation). One lead panel was connected to a DC power supply as the anode and the other was a cathode. A potential of 20 volts was initially applied to produce a current that ranged 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. The ESCA analysis was carried out on the lead surface. The photoelectronic binding energy of the silicon was used to characterize the nature of the species formed within the mineralized layer. These species were identified as a lead disilicate modified by the presence of sodium ion by the binding energy of 102.0 eV for the photoelectron Si (2p).

EXAMPLE 4 This Example demonstrates the formation of a mineral surface on an aluminum substrate. Using the same apparatus as in Example 1, aluminum coupons (7.62 cm x 15.24 cm (3"x 6")) were reacted to form a metal silicate surface. Two different alloys of aluminum, Al 2024 and A17075 were used. Before the panels were subjected to the electrolytic process, each panel was prepared using the methods set forth below in Table A. Each panel was washed with alcohol reagent to remove any excess dust and oils. The panels were cleaned with Alumiprep 33, subjected to anodic cleaning or both. Both forms of cleaning were designed to remove excess aluminum oxides. Anodic cleaning was carried out by placing the work panel as an anode in an aqueous solution containing 5% NaOH, 2.4% Na2CO3, 2% Na2Si03, 0.6% Na3P04, and applying a potential to maintain a current density of 100mA / cm2 through the submerged 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 connected to the negative cable of a CD power supply by means of a wire while the other panel was connected to the positive cable. The two panels were placed 5.08 centimeters (2 inches) apart from each other. The potential was set at the voltage shown in the table and the cell was operated for one hour.

TABLE 1 Example A B C D E H Alloy type 2024 2024 2024 2024 7075 7075 7075 7075 Anodic Cleaning Yes Yes No No Yes Yes No No Washing Acid Yes Yes Yes Yes Yes Yes Yes Yes Bath solution Na2Si03 1% 10í 10% 1 í 10% 10í H202 1% 0% 0% i s- 12- 0% 19- Potential 12V 18V 12V 18V 12V 18V 12V 18V The ESCA was used to analyze the surface of each of the substrates. Each measured sample showed a mixture of silica and metallic silicate. Without wishing to be bound by any theory or explanation, it is believed that the metal silicate is the result of the reaction between the metal cations on the surface and the alkali metal silicates in the coating. It is also believed that silica is the result of excess silicates from the reaction or precipitated silica from the coating removal process. The metal silicate is indicated by a binding energy (BE) of Si (2p) in the low range of 102 eV, typically between 102.1 to 102.3. The silica can be observed by the BE of the Si (2p) between 103.3 to 103.6 eV. The resulting spectra show superimposed peaks, then deconvolution reveals binding energies in the representative range of metallic silicate and silica.

EXAMPLE 5 This Example illustrates an alternative to immersion to create the silicate-containing medium. An aqueous gel made of 5% sodium silicate and 10% fumed silica was used to coat cold-rolled steel panels. One panel was washed with alcohol reagent, while the other panel was washed in a metal preparation based on phosphoric acid, followed by a wash with sodium hydroxide and a bath of hydrogen peroxide. The apparatus was adjusted using a DC power source connecting the positive cable to the steel panel and the negative cable to a platinum wire wound with glass wool. This operation was designed to simulate a brush coating. The "brush" was immersed in the gel solution to allow complete saturation. The potential was set at 12V and the gel was painted on the panel with the brush. When the brush passed over the surface of the panel, the release of hydrogen gas could be observed. The gel was worked with the brush for five minutes and the panel was then washed with DI water to remove any excess of unreacted silica and silicates. The ESCA was used to analyze the surface of each steel panel. The ESCA detects the reaction products between the metallic substrate and the environment created by the electrolytic process. Each measured sample showed a mixture of silica and metallic silicate. The metal silicate is a result of the reaction between the metal cations on the surface and the alkali metal silicates in the coating. Silica is a result of any excess silicates from the reaction or precipitated silica from the coating removal process. The metal silicate is indicated by a binding energy (BE) of Si (2p) in the low range of 102 eV, typically between 102.1 to 102.3. The silica can be observed by the BE of the Si (2p) of between 103.3 to 103.6 eV. The resulting spectra show superposition of peaks, then deconvolution reveals binding energies at the representative intervals of metallic silicate and silica.

EXAMPLE 6 Using the same apparatus as Example 1, coupons of cold rolled steel (ACT Laboratories) were reacted to form the metal silicate surface. Before the panels were subjected to the electrolytic process, each panel was prepared using the methods set forth below in Table B. Each panel was washed with alcohol reagent to remove any excess dust and oils. The panels were cleaned with Metalprep 79 (Parker Amchem), subjected to an anodic cleaning or both. Both forms of cleaning were designed to remove excess aluminum oxides. Anodic cleaning was carried out by placing the work panel as an anode in an aqueous solution containing 5% NaOH, 2.4% Na2CO3, 2% Na2Si03, 0.6% Na3P0, and applying a potential to maintain a current density of 100mA / cm2 through the submerged 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 connected to the negative cable of a CD power supply by means of a wire while the other panel was connected to the positive cable. The two panels separated 5.08 centimeters (2 inches) apart. The potential was set at the voltage shown in the table and the cell was operated for one hour.

TABLE B Example AA BB CC DD EE Substrate type CRS CRS CRS CRSJ CRS ' Anodic Cleaning No Yes No No No Washing Acid Yes Yes Yes No No Bath solution Na2Si03 11 S? - 10% 112-í Potential (V) 14-24 6 (CV) 12V (CV) Current Density 23 (CC) 23-10 85-4? (mA / cm2) B117 2 hrs 1 hr 1 hr 0.25 hr 0.25 hr The Cold Rolled Steel Control - This panel was not treated. Cold Rolled Steel with iron phosphate treatment (ACT Laboratories) - No additional treatments were performed.

The electrolytic process was carried out as a constant current or constant voltage experiment, designated by the CV symbol or in CC in the table. The constant voltage experiments applied a constant potential to the cell allowing the current to fluctuate while? that experiments at constant current maintained the current by adjusting the potential. The panels were tested to determine corrosion protection using ASTM B117. Failures were determined in 5% coverage of the red oxide surface. The ESCA was used to analyze the surface of each of the substrates. The ESCA detects the reaction products between the metallic substrate and the environment created by the electrolytic process. Each measured sample showed a mixture of silica and metallic silicate. The metal silicate is a result of the reaction between the metal cations on the surface and the alkali metal silicates in the coating. Silica is a result of excess silicates from the reaction or precipitated silica from the coating removal process. The metal silicate is indicated by a binding energy (BE) of Si (2p) in the low range of 102 eV, typically between 102.1 to 102.3. The silica can be observed by the BE of the Si (2p) of between 103.3 to 103.6 eV. The resulting spectra show superposition of peaks, then deconvolution reveals binding energies at representative intervals of metallic silicate and silica.

EXAMPLE 7 Using the same apparatus as Example 1, galvanized zinc steel coupons (EZG 60G ACT Laboratories) were made to form the metal silicate surface. Before the panels were subjected to the electrolytic process, each panel was prepared using the methods set forth below in Table C. Each panel was washed with alcohol reagent to remove any excess dust 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 connected to the negative cable of a CD power supply by means of a wire while the other panel was connected to the positive cable. The two panels separated approximately 5.08 centimeters (2 inches) apart. The potential was set to the voltage shown in the table and the cell was operated for one hour.

TABLE C Example Al B2 C3 D5 Substrate type GS GS GS GSJ Bath solution Na2Si03 10% 1% 105 Potential (V) 6 (CV) 10 (CV) 18 (CV) Current Density (mA / cm) 22-3 7-3 142-3 B117 336 hrs 224 hrs 216 hrs 96 hrs Galvanized Steel Control - No treatment was done to this panel.

The panels were tested to determine corrosion protection using ASTM B117. Failures were determined in 5% coverage of the red oxide surface. The ESCA was used to analyze the surface of each of the substrates. The ESCA detects the reaction products between the metallic substrate and the environment created by the electrolytic process. Each measured sample showed a mixture of silica and metallic silicate. The metal silicate is a result of the reaction between the metal cations on the surface and the alkali metal silicates in the coating. Silica is a result of excess silicates from the reaction or precipitated silica from the coating removal process. The metal silicate is indicated by a binding energy (BE) of Si (2p) in the low range of 102 eV, typically between 102.1 to 102.3. The silica can be observed by the BE of the Si (2p) of between 103.3 to 103.6 eV. The resulting spectra show superposition of peaks, then deconvolution reveals binding energies at representative intervals of metallic silicate and silica.

EXAMPLE 8 Using the same apparatus as Example 1, copper coupons (C110 Hard, Fullerton Metals) were reacted to form the metal silicate surface. Before the panels were subjected to the electrolytic process, each panel was prepared using the methods set forth in Table D below. Each panel was washed with alcohol reagent to remove any excess dust 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 connected to the negative cable of a CD power supply by means of a wire while the other panel was connected to the positive cable. The two panels separated approximately 5.08 centimeters (2 inches) apart. The potential was set to the voltage shown in the table and the cell was operated for one hour.

TABLE D Example AA1 BB2 CC3 DD4 EE5 Substrate type Cu Cu Cu Cu Cu Cu1 Bath solution Na2Si03 10% 10% Potential (V) 12 (CV) 6 (CV) 6 (CV) 36 (CV) Current Density 40 -17 19- 9 4 -1 36-10 (mA / crn2) B117 11 hrs 11 hrs 5 hrs 5 hrs 2 hrs 1 Copper Control- No treatment was done to this panel.

The panels were tested to determine corrosion protection using ASTM B117. Faults were determined by the presence of copper oxide which was indicated by the appearance of a thick mist on the surface. The ESCA was used to analyze the surface of each of the substrates. The ESCA allows us to examine the reaction products between the metallic substrate and the environment created by the electrolytic process. Each measured sample showed a mixture of silica and metallic silicate. The metal silicate is a result of the reaction between the metal cations on the surface and the alkali metal silicates in the coating. Silica is a result of excess silicates from the reaction or precipitated silica from the coating removal process. The metal silicate is indicated by a binding energy (BE) of Si (2p) in the low range of 102 eV, typically between 102.1 to 102.3. The silica can be observed by the BE of the Si (2p) of between 103.3 to 103.6 eV. The resulting spectra show superposition of peaks, then deconvolution reveals binding energies at representative intervals of metallic silicate and silica.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (22)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. An electrically improved cathodic method for forming a corrosion-resistant surface on a metal surface, characterized in that it comprises: contacting the metal surface with an aqueous medium containing silicate, passing a current through the surface and the medium a speed sufficient to release hydrogen from the medium and for a sufficient period of time to form a mineral on the surface, where the mineral comprises crystals included within an amorphous matrix and the mineral imparts enhanced corrosion resistance to the surface.

2. A method for improving the corrosion resistance of an electrically conductive surface, characterized in that it comprises: immersing the metal surface in a medium containing alkali silicate, passing a current through the surface and the medium, where the The metal surface reacts with a portion of the metal surface to form a mineral layer comprising crystals included within an amorphous matrix and having improved corrosion resistance compared to the metal surface.

3. A cathode method for improving the corrosion resistance of a metal surface, characterized in that it comprises: exposing the metal surface to an aqueous medium containing silicate, establishing an electrolytic environment where the surface is used as a cathode, passing a current through the silicate medium and the surface at a rate sufficient to release hydrogen from the medium and for a period of time and under conditions sufficient to form a corrosion-resistant surface on the metal surface, where the corrosion-resistant surface comprises , a mineral.

4. The method according to claim 1, 2 or 3, characterized in that the silicate-containing medium comprises sodium silicate.

The method according to claim 1, 2 or 3, characterized in that the metal surface comprises at least one member selected from the group consisting of lead, copper, zinc, aluminum and steel.

6. The method according to claim 1, 2 or 3, characterized in that the metal surface comprises at least one member selected from the group consisting of galvanized metal, zinc, iron, steel, bronze, copper, nickel, tin, aluminum, lead , cadmium, magnesium and alloys thereof.

The method according to claim 1, 2 or 3, characterized in that the metal surfaces comprise zinc.

8. The method of compliance with the claim 1, 2 or 3, characterized in that it also comprises cleaning the metal surface anodically before forming the mineral.

9. The method according to claim 1, 2 or 3, characterized in that the step is carried out at a voltage greater than 6V.

The method according to claim 1, 2 or 3, characterized in that the surface has an ASTM B117 exposure time greater than 2 hours.

11. The method according to the claim 1, 2 or 3, characterized in that the silicate-containing medium comprises more than 5% by weight of at least one alkali silicate.

12. The method according to claim 1, 2 or 3, characterized in that the silicate-containing medium comprises silica and at least one silicate.

The method according to claim 1, 2 or 3, characterized in that the silicate-containing medium is substantially free of solvent.

The method according to claim 1, 2 or 3, characterized in that the silicate-containing medium comprises at least one member of the group consisting of a fluid, gel or spray bath.

15. The method according to claim 1, 2 or 3, characterized in that the silicate-containing medium further comprises at least one adulterant.

16. The method according to claim 1, 2 or 3, characterized in that the silicate-containing medium further comprises at least one water-dispersible polymer.

17. The method according to claim 16, characterized in that the polymer comprises polyurethane.

18. The method according to claim 15, characterized in that the adulterant comprises the anode of the electrolytic environment.

19. The method according to claim 1, 2 or 3, characterized in that it also comprises applying a secondary coating.

20. The method according to claim 1, 2 or 3, characterized in that the step is achieved by direct current (DC).

The method according to claim 15, characterized in that the adulterant comprises at least one member selected from the group consisting of water-soluble salts and oxides of tungsten, molybdenum, chromium, titanium, zirconium, vanadium, phosphorus, aluminum, iron , boron, bismuth, gallium, tellurium, germanium, antimony, niobium, magnesium and manganese.

22. The method according to claim 15 or 18, characterized in that the adulterant comprises at least one of iron and aluminum.