CA2023203A1 - Method of protecting an aluminum surface - Google Patents
Method of protecting an aluminum surfaceInfo
- Publication number
- CA2023203A1 CA2023203A1 CA 2023203 CA2023203A CA2023203A1 CA 2023203 A1 CA2023203 A1 CA 2023203A1 CA 2023203 CA2023203 CA 2023203 CA 2023203 A CA2023203 A CA 2023203A CA 2023203 A1 CA2023203 A1 CA 2023203A1
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- CA
- Canada
- Prior art keywords
- alloy
- bath
- sulfuric acid
- columnar substrate
- sodium dichromate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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- Chemical Treatment Of Metals (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
ABSTRACT
A method of providing corrosion protection for a specific aluminum base alloy while at the same time creating an olive drab color in the alloy. Samples of the aluminum base alloy after being cleaned were placed in a bath containing sulfuric acid. The reaction of the sulfuric acid with the aluminum base alloy creates a columnar substrate on the surface of the samples. The samples were removed from the sulfuric acid bath and neutralized in a sodium bicarbonate bath. Thereafter the samples were placed in a bath containing sodium dichromate and a surfactant. The surfactant lowers the surface tension sufficiently for the sodium dichromate to flow into the interstices of the columnar substrate to seal the surface from the surrounding environment while at the same time reacting to produce the olive drab color.
A method of providing corrosion protection for a specific aluminum base alloy while at the same time creating an olive drab color in the alloy. Samples of the aluminum base alloy after being cleaned were placed in a bath containing sulfuric acid. The reaction of the sulfuric acid with the aluminum base alloy creates a columnar substrate on the surface of the samples. The samples were removed from the sulfuric acid bath and neutralized in a sodium bicarbonate bath. Thereafter the samples were placed in a bath containing sodium dichromate and a surfactant. The surfactant lowers the surface tension sufficiently for the sodium dichromate to flow into the interstices of the columnar substrate to seal the surface from the surrounding environment while at the same time reacting to produce the olive drab color.
Description
METHOD OF PROTECTING AN ~LUMINUM SURFACE
This invention relates to a method of sealing and protecting the surface of an aluminum base alloy from the environment while at the same time creating a camouflage 05 color on the surface of the alloy. The aluminum base alloy is derived from the following formula: Al, Fe, Si, and at least one element or compound selected from a group consisting of Mn; V; Cr; W; Nb; Ta; and SiC.
High strength and ductile rapid solidified aluminum based alloys are replacing many specialty metals in components for the aerospace projects. One such aluminum based alloy is disclosed in U.S. Patent 4,729,790 which maintains both strength and ductility at both ambient and at temperatures up to 400C in order to protect the surface of such an alloy from corrosion, it is normal to coat the surface with some type of protection.
The protection is achieved through an anodic coating such -~;
as disclosed in U.S. Patents 3,625,841; 3,761,362; and 4,571,287. The anodic oxide film or coating is developed on the aluminum article by electrolysis while the article is the anode in an aqueous solution containing one or more acids and a metal salt as the electrolyte. The resulting color of the coated article as disclosed in U.S. Patent 4,571,287 is essentially determined by time and the metal salt used as an electrolyte. For instance, many outdoor signs such as used as highway information conduits are colored green. One such way that outdoor signs were colored green was to apply an epoxy paint to such signs, ~-this method was acceptable however the environment caused 30 the paint to fade and as a result the information -contained thereon was hard to read after a period of time without refurbishment or the paint was scraped off and the surface directly exposed to the environment. Later, as disclosed in U.S. Patent 4,043,880 the green color is made 35 part of the protection process for the aluminum through ~ -the addition of copper ions during an anodization process. This process of providing a dark green color is an acceptable method of coloring many aluminum articles 2 ~ g used in industry. Unfortunately, when copper ions are used to color an aluminum article, the aluminum article cannot be used in a fuel control of an aircraft without causing problems. Thus, the use of this coloration 05 process and protection afforded thereby is limited to components that are not in contact with fuel that is used in an aircraft.
In an effort to develop a corrosion protection system for the aluminum based alloy disclosed in U.S.
Patent 4,729,790 it was discovered that an olive drab color was imparted to the alloy when the alloy was anodized in a sulfuric acid bath, followed by neutralization in a cold water bath of sodium bicarbonate and sealed with a solution of sodium dichromate. The 15 olive drab color of the article was unexpected in the ~
absence of copper ions in any of the baths used in --~-developing the protection system. On inspection of the article was discovered that the olive drab color extended throuqhout the entire anodized surface layer formed on the aluminum based alloy.
An advantage of this method of this corrosion protection for an aluminum based alloy resides in the olive drab color imparted to the aluminum based alloy during a direct current electrolysis and sealing process wiihout the need of copper ions in a sulfuric acid bath.
It is an object of this invention to provide corrosion protection for a rapid solidified aluminum alloy to allow components made therefrom to operate in hostile environments without oxidatizing.
It is another object of this invention to provide an aluminum alloy with an anodization process wherein an olive drab color imparted to the alloy is not effected by corrosive environments under operating conditions wherein temperatures reach 400C. -~
These advantages and objects should be apparent from reading this specification.
Recognizing the strength and stability of the aluminum based alloy disclosed in U.S. Patent 4,729,790 ~,J~/~, when exposed to temperatures up to 225C, the mechanical properties and fracture resistance thereof lends application to many aerospace components. The strength and stability of this alloy is due to the slower 05 coarsening rate of the silicides compared to the dispersoids found in other high temperature aluminum alloys. This alloy is devoid of any coarse needle or plate-like intermetallic phases which degrade alloy ductility and fracture toughness. Further, this ~ -particular alloy contains high transition concentrations of iron that form high volume fractions of silicides to -maintain the mechanical properties during high temperature exposure. For many aerospace applications corrosion protection of components is required to meet operational standards.
Because of the simplicity and safety involved it was decided that the corrosion protection for this alloy could best be achieved through anodization in an electrolyte by direct current electrolysis. An article made from this aluminum alloy is located in an aqueous solution containing a low concentration sulfuric acid and connected as the cathode to a voltage source. The resulting anodic film formed on the surface of the ~
aluminum alloy while initially colorless when placed in a ;
bath containing sodium dichromate for about twenty minutes changes to olive drab.
In order to evaluate the proposed process of providing anodized protection for the aluminum base alloy, samples of an aluminum based alloy as disclosed in U.S.
Patent 4,729,790 were obtained. The weight percentages of the ingredients for the samples were:
Fe = 8.53;
V = 1.2;
Si = 1.8; and Al = 88.47 Total = 100.00 2~?~r;3 Samples of this aluminum based alloy were evaluated, without a coating, having a hard anodize coating, according to the general accepted process of sulfuric acid and oxalic acid anodize treatments and an 05 anodize coating according to the principals of this invention using sulfuric acid treatments to establish corrosion protection. The resulting treatments produced a coating on the surface of the alloy samples approximately 0.0001" or 0.000254 cm. The samples with the hard anodize coating and sulfuric acid coating of this invention which unexpectedly changed to an olive drab color without the addition of any dye or reaction with copper ions as was previously required to obtain a green surface color. The -~
samples along with an treated or bare sample was subjected to salt spra~ testing according to test procedure defined by ASTM B117 and U.S. Mil-A-8625E standard. The bare sample failed the test after 24 hours while the samples with the hard anodized coating and sulfuric acid anodized coating showed no visual effects after being subjected to -336 hours of salt spray as required by the test procedure. The olive drab color which was uniform throughout the entire anodized coatings and did not fade during the salt spray test. Further, this olive drab color is substantially identical to the camouflage color used on many military vehicles and installations to hinder observation thereof.
The specific sulfuric acid anodize treatment process performed on the samples is as follows:
Samples were passed through a vapor degreasing chamber of 1,1,1 trichloroethane to remove any oils that may have been deposited on the surface of the sample after the manufacture thereof. After passing through the degreasing chamber the sample was placed in an inhibited alkaline bath to further clean the alloy. The alkaline bath includes a cleansing product sold under the name of Aldet. 4-6 oz/gal or 50-80 gmfl of Aldet produces a concentration to maintain a 12 pH in the alkaline bath.
The temperature in the al~aline ~ath was maintained ~ ~' .~' . ' .. ;, , 2 '~ ~ 'i "' Q ~
between 48-60C and the samples were cleaned in about 5 minutes. After the samples were removed from the inhibited alkaline bath they were rinsed in a water bath to stop the cleaning action and substantially return the 05 alloy to a neutral state before being placed in a deoxidizing bath having a minimum temperature of 20C ~ ~
containing a deoxidizing agent sold under the name of -Alutone for 3 minutes . A concentration 10% + 1% of Alutone is sufficient to remove any oxidation and contamination that may be located on the surace of the alloy either during manufacture or as a result of exposure to the environment. After deoxidation, the cleaned samples were placed in a bath containing sulfuric acid having a concentration of from 150-250 g/liter and a temperature of between 20-25C. At room temperature and concentration the sulfuric acid bath is a relative safe -operation. The samples were connected to the anode of a voltage source. The voltage between the anode and cathode -~
is gradually increased from zero to 20 volts at a slow rate of approximately 3 volts per minute and this voltage is maintained for about 30 minutes. The voltage between the anode and cathode can vary between 18-25 volts dispensing on the time available for the development of a columnar substrate on the surface of the alloy. The columnar substrate which has a nominal height of 0.00016 inches or 0.0004 cm forms an initial level of protection on the surface of this alloy.
After the substrate has been formed, the alloy is removed from the sulfuric bath and rinsed in a cold water bath to interrupt the reaction between the sulfuric acid and alloy and to terminate the development of the columnar substrate. Throughout this specification where the term cold water bath is used the temperature of the water is below 20C while a room or warm water bath indicates the temperature to be above 2GC. The cold water bath effectively removes the sulfuric acid from the surface of the alloy however some sulfuric acid may be trapped between the individual columns in the columnar substrate.
To assure total reaction termination, the samples were passed through a room temperature bath with a concentration of between 40-60 grams/liter of sodium ~
bicarbonate. After about one minute the sodium ~ --05 bicarbonate should have reacted with and neutralized any sulfuric acid that may have been retained in the ~-interstices of the columnar substrate on the surface of the samples.
The reaction between the sodium bicarbonate and sulfuric acid produces a sodium sulphate residue which along with any residual sodium bicarbonate is rinsed away in a warm water bath. On removal of the samples from this bath, the anodized surface layer is essentially gray in color.
The gray colored samples were placed in bath containing sodium dichromate and a surfactant. A 5%
concentration of sodium dichromate adjusted with sodium hydroxide to create a pH of between 5-6 in the bath when a minimum temperature of 90C is maintained should be sufficient to seal the columnar substrate. A 0.01%
concentration of the surfactant, a product sold under the trade name of Intravon was used, low~red the surface tension on the columnar substrate such that after about 20 minutes, the sodium dichromate flowed into and filled the interstices and sealed the surface of the samples from the surrounding environment. This bath because of the sodium -dichromate, surfactant and water has an orange color however on removal of the samples from the bath, its color was surprising olive drab.
The samples now colored olive drab on its removal from the sodium dichromate bath were first placed in a warm water bath, below 20C, bath to remove and excess sodium dichromate from the now sealed columnar substrate.
Thereafter the samples were then placed in a hot water bath, where the temperature of the water is maintained above 50C, to uniformly raise the temperature of the samples. When a desired temperature is reached, the samples were removed from the hot water bath and 2 ~ ~ ~ s.3 ~
- 7 - ::
transported to a chamber where circulating warm air above 25C, air dried the samples.
This anodizing process was used to seal and protect the samples from corrosion as required by ASTM
05 B117 and Mil A-8625E. On inspection of the samples after the salt spray test was performed, no measurable weight loss was found in the samples nor was visible corrosion observed.
In order to confirm the results and protection for the aluminum based alloy using this anodizing process, different samples based on the composition disclosed in U.S. Patent 4,729,790 was obtained however 11% by volume of silicon carbide was included in the basic composition.
The samples of this alloy were anodized in accordance with the process set forth above and subjected to the ASTM B117 salt fog test for the required 336 hours. On visual inspection, no corrosion was observed on the samples and no weight change occurred as a result of the salt spray test. The measured thickness of the anodized layer was found to be 0.00016 inches or 0.0004 cm. The olive drab color was consistent throughout the layer of anodic film or coating on these samples and the only way the coating was removed from the samples was by a mechanical scraper.
Thus, the method of anodizing an aluminum based alloy as described above in addition to providing for corrosion protection also colors the alloy without the need for dye to an olive drab color which is universally accepted as a camouflage for most military vehicles and installations.
This invention relates to a method of sealing and protecting the surface of an aluminum base alloy from the environment while at the same time creating a camouflage 05 color on the surface of the alloy. The aluminum base alloy is derived from the following formula: Al, Fe, Si, and at least one element or compound selected from a group consisting of Mn; V; Cr; W; Nb; Ta; and SiC.
High strength and ductile rapid solidified aluminum based alloys are replacing many specialty metals in components for the aerospace projects. One such aluminum based alloy is disclosed in U.S. Patent 4,729,790 which maintains both strength and ductility at both ambient and at temperatures up to 400C in order to protect the surface of such an alloy from corrosion, it is normal to coat the surface with some type of protection.
The protection is achieved through an anodic coating such -~;
as disclosed in U.S. Patents 3,625,841; 3,761,362; and 4,571,287. The anodic oxide film or coating is developed on the aluminum article by electrolysis while the article is the anode in an aqueous solution containing one or more acids and a metal salt as the electrolyte. The resulting color of the coated article as disclosed in U.S. Patent 4,571,287 is essentially determined by time and the metal salt used as an electrolyte. For instance, many outdoor signs such as used as highway information conduits are colored green. One such way that outdoor signs were colored green was to apply an epoxy paint to such signs, ~-this method was acceptable however the environment caused 30 the paint to fade and as a result the information -contained thereon was hard to read after a period of time without refurbishment or the paint was scraped off and the surface directly exposed to the environment. Later, as disclosed in U.S. Patent 4,043,880 the green color is made 35 part of the protection process for the aluminum through ~ -the addition of copper ions during an anodization process. This process of providing a dark green color is an acceptable method of coloring many aluminum articles 2 ~ g used in industry. Unfortunately, when copper ions are used to color an aluminum article, the aluminum article cannot be used in a fuel control of an aircraft without causing problems. Thus, the use of this coloration 05 process and protection afforded thereby is limited to components that are not in contact with fuel that is used in an aircraft.
In an effort to develop a corrosion protection system for the aluminum based alloy disclosed in U.S.
Patent 4,729,790 it was discovered that an olive drab color was imparted to the alloy when the alloy was anodized in a sulfuric acid bath, followed by neutralization in a cold water bath of sodium bicarbonate and sealed with a solution of sodium dichromate. The 15 olive drab color of the article was unexpected in the ~
absence of copper ions in any of the baths used in --~-developing the protection system. On inspection of the article was discovered that the olive drab color extended throuqhout the entire anodized surface layer formed on the aluminum based alloy.
An advantage of this method of this corrosion protection for an aluminum based alloy resides in the olive drab color imparted to the aluminum based alloy during a direct current electrolysis and sealing process wiihout the need of copper ions in a sulfuric acid bath.
It is an object of this invention to provide corrosion protection for a rapid solidified aluminum alloy to allow components made therefrom to operate in hostile environments without oxidatizing.
It is another object of this invention to provide an aluminum alloy with an anodization process wherein an olive drab color imparted to the alloy is not effected by corrosive environments under operating conditions wherein temperatures reach 400C. -~
These advantages and objects should be apparent from reading this specification.
Recognizing the strength and stability of the aluminum based alloy disclosed in U.S. Patent 4,729,790 ~,J~/~, when exposed to temperatures up to 225C, the mechanical properties and fracture resistance thereof lends application to many aerospace components. The strength and stability of this alloy is due to the slower 05 coarsening rate of the silicides compared to the dispersoids found in other high temperature aluminum alloys. This alloy is devoid of any coarse needle or plate-like intermetallic phases which degrade alloy ductility and fracture toughness. Further, this ~ -particular alloy contains high transition concentrations of iron that form high volume fractions of silicides to -maintain the mechanical properties during high temperature exposure. For many aerospace applications corrosion protection of components is required to meet operational standards.
Because of the simplicity and safety involved it was decided that the corrosion protection for this alloy could best be achieved through anodization in an electrolyte by direct current electrolysis. An article made from this aluminum alloy is located in an aqueous solution containing a low concentration sulfuric acid and connected as the cathode to a voltage source. The resulting anodic film formed on the surface of the ~
aluminum alloy while initially colorless when placed in a ;
bath containing sodium dichromate for about twenty minutes changes to olive drab.
In order to evaluate the proposed process of providing anodized protection for the aluminum base alloy, samples of an aluminum based alloy as disclosed in U.S.
Patent 4,729,790 were obtained. The weight percentages of the ingredients for the samples were:
Fe = 8.53;
V = 1.2;
Si = 1.8; and Al = 88.47 Total = 100.00 2~?~r;3 Samples of this aluminum based alloy were evaluated, without a coating, having a hard anodize coating, according to the general accepted process of sulfuric acid and oxalic acid anodize treatments and an 05 anodize coating according to the principals of this invention using sulfuric acid treatments to establish corrosion protection. The resulting treatments produced a coating on the surface of the alloy samples approximately 0.0001" or 0.000254 cm. The samples with the hard anodize coating and sulfuric acid coating of this invention which unexpectedly changed to an olive drab color without the addition of any dye or reaction with copper ions as was previously required to obtain a green surface color. The -~
samples along with an treated or bare sample was subjected to salt spra~ testing according to test procedure defined by ASTM B117 and U.S. Mil-A-8625E standard. The bare sample failed the test after 24 hours while the samples with the hard anodized coating and sulfuric acid anodized coating showed no visual effects after being subjected to -336 hours of salt spray as required by the test procedure. The olive drab color which was uniform throughout the entire anodized coatings and did not fade during the salt spray test. Further, this olive drab color is substantially identical to the camouflage color used on many military vehicles and installations to hinder observation thereof.
The specific sulfuric acid anodize treatment process performed on the samples is as follows:
Samples were passed through a vapor degreasing chamber of 1,1,1 trichloroethane to remove any oils that may have been deposited on the surface of the sample after the manufacture thereof. After passing through the degreasing chamber the sample was placed in an inhibited alkaline bath to further clean the alloy. The alkaline bath includes a cleansing product sold under the name of Aldet. 4-6 oz/gal or 50-80 gmfl of Aldet produces a concentration to maintain a 12 pH in the alkaline bath.
The temperature in the al~aline ~ath was maintained ~ ~' .~' . ' .. ;, , 2 '~ ~ 'i "' Q ~
between 48-60C and the samples were cleaned in about 5 minutes. After the samples were removed from the inhibited alkaline bath they were rinsed in a water bath to stop the cleaning action and substantially return the 05 alloy to a neutral state before being placed in a deoxidizing bath having a minimum temperature of 20C ~ ~
containing a deoxidizing agent sold under the name of -Alutone for 3 minutes . A concentration 10% + 1% of Alutone is sufficient to remove any oxidation and contamination that may be located on the surace of the alloy either during manufacture or as a result of exposure to the environment. After deoxidation, the cleaned samples were placed in a bath containing sulfuric acid having a concentration of from 150-250 g/liter and a temperature of between 20-25C. At room temperature and concentration the sulfuric acid bath is a relative safe -operation. The samples were connected to the anode of a voltage source. The voltage between the anode and cathode -~
is gradually increased from zero to 20 volts at a slow rate of approximately 3 volts per minute and this voltage is maintained for about 30 minutes. The voltage between the anode and cathode can vary between 18-25 volts dispensing on the time available for the development of a columnar substrate on the surface of the alloy. The columnar substrate which has a nominal height of 0.00016 inches or 0.0004 cm forms an initial level of protection on the surface of this alloy.
After the substrate has been formed, the alloy is removed from the sulfuric bath and rinsed in a cold water bath to interrupt the reaction between the sulfuric acid and alloy and to terminate the development of the columnar substrate. Throughout this specification where the term cold water bath is used the temperature of the water is below 20C while a room or warm water bath indicates the temperature to be above 2GC. The cold water bath effectively removes the sulfuric acid from the surface of the alloy however some sulfuric acid may be trapped between the individual columns in the columnar substrate.
To assure total reaction termination, the samples were passed through a room temperature bath with a concentration of between 40-60 grams/liter of sodium ~
bicarbonate. After about one minute the sodium ~ --05 bicarbonate should have reacted with and neutralized any sulfuric acid that may have been retained in the ~-interstices of the columnar substrate on the surface of the samples.
The reaction between the sodium bicarbonate and sulfuric acid produces a sodium sulphate residue which along with any residual sodium bicarbonate is rinsed away in a warm water bath. On removal of the samples from this bath, the anodized surface layer is essentially gray in color.
The gray colored samples were placed in bath containing sodium dichromate and a surfactant. A 5%
concentration of sodium dichromate adjusted with sodium hydroxide to create a pH of between 5-6 in the bath when a minimum temperature of 90C is maintained should be sufficient to seal the columnar substrate. A 0.01%
concentration of the surfactant, a product sold under the trade name of Intravon was used, low~red the surface tension on the columnar substrate such that after about 20 minutes, the sodium dichromate flowed into and filled the interstices and sealed the surface of the samples from the surrounding environment. This bath because of the sodium -dichromate, surfactant and water has an orange color however on removal of the samples from the bath, its color was surprising olive drab.
The samples now colored olive drab on its removal from the sodium dichromate bath were first placed in a warm water bath, below 20C, bath to remove and excess sodium dichromate from the now sealed columnar substrate.
Thereafter the samples were then placed in a hot water bath, where the temperature of the water is maintained above 50C, to uniformly raise the temperature of the samples. When a desired temperature is reached, the samples were removed from the hot water bath and 2 ~ ~ ~ s.3 ~
- 7 - ::
transported to a chamber where circulating warm air above 25C, air dried the samples.
This anodizing process was used to seal and protect the samples from corrosion as required by ASTM
05 B117 and Mil A-8625E. On inspection of the samples after the salt spray test was performed, no measurable weight loss was found in the samples nor was visible corrosion observed.
In order to confirm the results and protection for the aluminum based alloy using this anodizing process, different samples based on the composition disclosed in U.S. Patent 4,729,790 was obtained however 11% by volume of silicon carbide was included in the basic composition.
The samples of this alloy were anodized in accordance with the process set forth above and subjected to the ASTM B117 salt fog test for the required 336 hours. On visual inspection, no corrosion was observed on the samples and no weight change occurred as a result of the salt spray test. The measured thickness of the anodized layer was found to be 0.00016 inches or 0.0004 cm. The olive drab color was consistent throughout the layer of anodic film or coating on these samples and the only way the coating was removed from the samples was by a mechanical scraper.
Thus, the method of anodizing an aluminum based alloy as described above in addition to providing for corrosion protection also colors the alloy without the need for dye to an olive drab color which is universally accepted as a camouflage for most military vehicles and installations.
Claims (7)
1. A method of coating an aluminum base alloy consisting of the formula: Al, Fe, Si and at least one element selected from a group consisting of Mn; V; Cr; W;
Nb; and Ta, said coating providing corrosion protection while producing an olive drab color over the entire surface of the alloy, said method comprising the steps of:
cleaning said alloy to remove any oxidation and contamination that may be located on the surface of the alloy;
placing the cleaned alloy in a bath of sulfuric acid having a concentration of 150-250 g/liter and a temperature of between 20-25°C, applying a voltage from 18-25 volts to said alloy for up to 30 minutes to create a columnar substrate on the surface of said alloy, said columnar substrate forming an initial level of protection for said alloy against corrosion;
moving said alloy from said sulfuric acid bath to a cold water bath to interrupt the reaction between said sulfuric acid and alloy and effectively terminate the development of the columnar substrate;
passing said alloy through a bath containing sodium bicarbonate to neutralize any sulfuric acid that may remain in the interstices of the columnar substrate and on the surface of the alloy;
moving said alloy through a cold water bath to remove any residual sodium bicarbonate from the interstices of the columnar substrate and surface of the alloy;
placing said alloy in a bath containing sodium dichromate and a surfactant, said sodium dichromate flowing into and filling said interstices to seal said surface of the alloy from the surrounding environment, said sodium dichromate reacting with said alloy to produce an olive drab color.
Nb; and Ta, said coating providing corrosion protection while producing an olive drab color over the entire surface of the alloy, said method comprising the steps of:
cleaning said alloy to remove any oxidation and contamination that may be located on the surface of the alloy;
placing the cleaned alloy in a bath of sulfuric acid having a concentration of 150-250 g/liter and a temperature of between 20-25°C, applying a voltage from 18-25 volts to said alloy for up to 30 minutes to create a columnar substrate on the surface of said alloy, said columnar substrate forming an initial level of protection for said alloy against corrosion;
moving said alloy from said sulfuric acid bath to a cold water bath to interrupt the reaction between said sulfuric acid and alloy and effectively terminate the development of the columnar substrate;
passing said alloy through a bath containing sodium bicarbonate to neutralize any sulfuric acid that may remain in the interstices of the columnar substrate and on the surface of the alloy;
moving said alloy through a cold water bath to remove any residual sodium bicarbonate from the interstices of the columnar substrate and surface of the alloy;
placing said alloy in a bath containing sodium dichromate and a surfactant, said sodium dichromate flowing into and filling said interstices to seal said surface of the alloy from the surrounding environment, said sodium dichromate reacting with said alloy to produce an olive drab color.
2. The method as recited in claim 1 wherein said bath containing said sodium dichromate has a pH of between 5-6.
3. The method as recited in claim 2 wherein said bath containing said sodium dichromate has a minimum temperature of 90°C.
4. The method as recited in claim 3 wherein said alloy is retained in said bath containing sodium dichromate for about 20 minutes.
5. The method as recited in claim 4 wherein the method further includes the steps of:
submerging said alloy in a warm water bath to remove any excess sodium dichromate from the surface of the interstices;
thereafter submerging said alloy in a hot water bath to raise the temperature of the alloy;
moving the alloy from the hot water water bath to a station where the surface is allowed to dry in the environment.
submerging said alloy in a warm water bath to remove any excess sodium dichromate from the surface of the interstices;
thereafter submerging said alloy in a hot water bath to raise the temperature of the alloy;
moving the alloy from the hot water water bath to a station where the surface is allowed to dry in the environment.
6. The method as recited in claim 5 wherein said surface is dried by flowing warm air over the surface to uniformly remove water.
7. A method of coating an aluminum base alloy consisting of the formula: Al, Fe, Si and at least one element selected from a group consisting of Mn: V; Cr; W;.
Nb; Ta; and SiC, said coating providing corrosion protection while producing an olive drab color over the entire surface of the alloy, said method comprising the steps of:
cleaning said alloy to remove any oxidation and contamination that may be located on the surface of the alloy;
placing the cleaned alloy in a bath of sulfuric acid having a concentration of 150-250 g/liter and a temperature of between 20-25°C;
applying a voltage from 18-25 volts to said alloy for up to 30 minutes to create a columnar substrate on the surface of said alloy, said columnar substrate forming an initial level of protection for said alloy against corrosion;
moving said alloy from said sulfuric acid bath to a cold water bath to interrupt the reaction between said sulfuric acid and alloy and effectively terminate the development of the columnar substrate;
passing said alloy through a bath containing sodium bicarbonate to neutralize any sulfuric acid that may remain in the interstices of the columnar substrate and on the surface of the alloy;
moving said alloy through a cold water bath to remove any residual sodium bicarbonate from the interstices of the columnar substrate and surface of the alloy;
placing said alloy in a bath containing sodium dichromate and a surfactant, said sodium dichromate flowing into and filling said interstices to seal said surface of the alloy from the surrounding environment, said sodium dichromate reacting with said alloy to produce an olive drab color.
Nb; Ta; and SiC, said coating providing corrosion protection while producing an olive drab color over the entire surface of the alloy, said method comprising the steps of:
cleaning said alloy to remove any oxidation and contamination that may be located on the surface of the alloy;
placing the cleaned alloy in a bath of sulfuric acid having a concentration of 150-250 g/liter and a temperature of between 20-25°C;
applying a voltage from 18-25 volts to said alloy for up to 30 minutes to create a columnar substrate on the surface of said alloy, said columnar substrate forming an initial level of protection for said alloy against corrosion;
moving said alloy from said sulfuric acid bath to a cold water bath to interrupt the reaction between said sulfuric acid and alloy and effectively terminate the development of the columnar substrate;
passing said alloy through a bath containing sodium bicarbonate to neutralize any sulfuric acid that may remain in the interstices of the columnar substrate and on the surface of the alloy;
moving said alloy through a cold water bath to remove any residual sodium bicarbonate from the interstices of the columnar substrate and surface of the alloy;
placing said alloy in a bath containing sodium dichromate and a surfactant, said sodium dichromate flowing into and filling said interstices to seal said surface of the alloy from the surrounding environment, said sodium dichromate reacting with said alloy to produce an olive drab color.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US52440390A | 1990-05-16 | 1990-05-16 | |
| US524,403 | 1990-05-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2023203A1 true CA2023203A1 (en) | 1991-11-17 |
Family
ID=24089072
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2023203 Abandoned CA2023203A1 (en) | 1990-05-16 | 1990-08-13 | Method of protecting an aluminum surface |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH0598498A (en) |
| CA (1) | CA2023203A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100648731B1 (en) * | 2005-03-21 | 2006-11-23 | 삼성에스디아이 주식회사 | Secondary battery and the fabrication method thereof |
| CN103526253B (en) * | 2013-07-19 | 2016-02-10 | 中国船舶重工集团公司第七0七研究所 | Enhancing aluminum-base composite material by silicon carbide particles hardening oxidation novel process |
-
1990
- 1990-08-13 CA CA 2023203 patent/CA2023203A1/en not_active Abandoned
-
1991
- 1991-05-14 JP JP13692391A patent/JPH0598498A/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0598498A (en) | 1993-04-20 |
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