Method of anodizing aluminum utilizing stabilized silicate solutions

Abstract

An anodizing solution, and method of anodizing, comprising suspending at least one aluminium substrate in an anodizing solution and applying an anodizing current to the anodizing solution. The anodizing solution comprises 0.01-5%, by weight, sodium silicate and 0.01-5%, by weight, α-amino acid.

Claimed is:  
     
         1 . An electrolyte composition comprising 0.01-5%, by weight, sodium silicate and 0.01-5%, by weight, α-amino acid.  
     
     
         2 . The electrolyte composition of  claim 1  comprising 0.1% and 1%, by weight, sodium silicate.  
     
     
         3 . The electrolyte composition of  claim 1  comprising 0.1% and 1%, by weight, α-amino acid.  
     
     
         4 . The electrolyte composition of  claim 1  wherein said α-amino acid comprises at least one compound selected from a group consisting of aspartic acid, glutamic acid, lysine, tyrosine, threonine, glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptothan, serine, cysteine, asparginine, glutamine, arginine, histidine, and α-aminoadipic acid.  
     
     
         5 . The electrolyte composition of  claim 4  wherein said α-amino acid is selected from a group consisting of aspartic acid, glutamic acid, lysine, tyrosine and threonine.  
     
     
         6 . The electrolyte composition of  claim 5  wherein said α-amino acid is selected from a group consisting of aspartic acid and glutamic acid.  
     
     
         7 . The electrolytic composition of  claim 6  wherein said α-amino acid is aspartic acid.  
     
     
         8 . The electrolyte composition of  claim 1  wherein said α-amino acid has a solubility of at least 0.04 g/100 ml H 2 O at 25° C.  
     
     
         9 . The electrolyte composition of  claim 1  wherein said composition has a pH of at least about 6 to no more than about 7.  
     
     
         10 . The electrolyte composition of  claim 1  further comprising an α-hydroxy carboxylic acid.  
     
     
         11 . The electrolyte composition of  claim 10  wherein said α-hydroxy carboxylic acid is present at a concentration of no more than about 5%, by weight.  
     
     
         12 . The electrolyte composition of  claim 10  wherein said α-hydroxy carboxylic acid is selected from a group consisting of malic acid, tartartic acid and citric acid.  
     
     
         13 . The electrolyte composition of  claim 12  wherein said α-hydroxy carboxylic acid is tartartic acid.  
     
     
         14 . A method of anodizing comprising suspending at least one aluminium substrate into an electrolytic solution and applying an anodizing current to the electrolytic solution wherein the electrolyte solution comprises 0.01-5%, by weight, sodium silicate and 0.01-5%, by weight, α-amino acid.  
     
     
         15 . The method of anodizing of  claim 14  comprising 0.1% and 1%, by weight, sodium silicate.  
     
     
         16 . The method of anodizing of  claim 14  comprising 0.1% and 1%, by weight, α-amino acid.  
     
     
         17 . The method of anodizing of  claim 14  wherein said α-amino acid comprises at least one compound selected from a group consisting of aspartic acid, glutamic acid, lysine, tyrosine, threonine, glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptothan, serine, cysteine, asparginine, glutamine, arginine, histidine, and α-aminoadipic acid.  
     
     
         18 . The method of anodizing of  claim 17  wherein said α-amino acid is selected from a group consisting of aspartic acid, glutamic acid, lysine, tyrosine and threonine.  
     
     
         19 . The method of anodizing of  claim 18  wherein said α-amino acid is selected from a group consisting of aspartic acid and glutamic acid.  
     
     
         20 . The method of anodizing of  claim 19  wherein said α-amino acid is aspartic acid.  
     
     
         21 . The method of anodizing of  claim 14  wherein said α-amino acid has a solubility of at least 0.04 g/100 ml H 2 O at 25° C.  
     
     
         22 . The method of anodizing of  claim 14  wherein said composition has a pH of at least about 6 to no more than about 7.  
     
     
         23 . The method of anodizing of  claim 14  further comprising an α-hydroxy carboxylic acid.  
     
     
         24 . The method of anodizing of  claim 23  wherein said α-hydroxy carboxylic acid is present at a concentration of no more than about 5%, by weight.  
     
     
         25 . The method of anodizing of  claim 23  wherein said α-hydroxy carboxylic acid is selected from a group consisting of malic acid, tartartic acid and citric acid.  
     
     
         26 . The method of anodizing of  claim 25  wherein said α-hydroxy carboxylic acid is tartartic acid.  
     
     
         27 . A method for forming an aluminium oxide barrier layer on an aluminium substrate comprising suspending at least one aluminium substrate into an electrolytic solution and applying an anodizing current to the electrolytic solution wherein the electrolyte solution comprises 0.01-5%, by weight, sodium silicate and 0.01-5%, by weight, α-amino acid.  
     
     
         28 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 27  wherein said aluminium oxide barrier layer comprises silicate.  
     
     
         29 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 28  wherein said aluminium oxide barrier layer comprises about 20 ppm to about 100 ppm silicate.  
     
     
         30 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 29  wherein said aluminium oxide barrier layer comprises about 50 to about 100 ppm silicate.  
     
     
         31 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 30  wherein said aluminium oxide barrier layer comprises about 60 ppm silicate.  
     
     
         32 . A capacitor comprising an aluminium substrate anodized by the method of  claim 27 .  
     
     
         33 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 27  comprising 0.1% and 1%, by weight, sodium silicate.  
     
     
         34 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 27  comprising 0.1% and 1%, by weight, α-amino acid.  
     
     
         35 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 27  wherein said α-amino acid comprises at least one compound selected from a group consisting of aspartic acid, glutamic acid, lysine, tyrosine, threonine, glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptothan, serine, cysteine, asparginine, glutamine, arginine, histidine, and α-aminoadipic acid.  
     
     
         36 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 35  wherein said α-amino acid is selected from a group consisting of aspartic acid, glutamic acid, lysine, tyrosine and threonine.  
     
     
         37 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 36  wherein said α-amino acid is selected from a group consisting of aspartic acid and glutamic acid.  
     
     
         38 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 37  wherein said α-amino acid is aspartic acid.  
     
     
         39 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 27  wherein said α-amino acid has a solubility of at least 0.04 g/100 ml H 2 O at 25° C.  
     
     
         40 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 27  wherein said composition has a pH of at least about 6 to no more than about 7.  
     
     
         41 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 27  further comprising an α-hydroxy carboxylic acid.  
     
     
         42 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 41  wherein said α-hydroxy carboxylic acid is present at a concentration of no more than about 5%, by weight.  
     
     
         43 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 41  wherein said α-hydroxy carboxylic acid is selected from a group consisting of malic acid, tartartic acid and citric acid.  
     
     
         44 . The method for forming an aluminium oxide barrier layer on an aluminium substrate of  claim 43  wherein said α-hydroxy carboxylic acid is tartartic acid.  
     
     
         45 . An aluminium substrate comprising an aluminium oxide barrier layer prepared by a method comprising suspending said aluminium substrate into an electrolytic solution and applying an anodizing current to the electrolytic solution wherein the electrolyte solution comprises 0.01-5%, by weight, sodium silicate and 0.01-5%, by weight, α-amino acid.  
     
     
         46 . The aluminium substrate of  claim 45  wherein said aluminium oxide barrier layer comprises silicate.  
     
     
         47 . The aluminium substrate of  claim 45  wherein said aluminium oxide barrier layer comprises about 20 ppm to about 100 ppm silicate.  
     
     
         48 . The aluminium substrate of  claim 47  wherein said aluminium oxide barrier layer comprises about 50 to about 100 ppm silicate.  
     
     
         49 . The aluminium substrate of  claim 48  wherein said aluminium oxide barrier layer comprises about 60 ppm silicate.  
     
     
         50 . A capacitor comprising an aluminium substrate anodized by the method of  claim 45 .  
     
     
         51 . The aluminium substrate of  claim 45  comprising 0.1% and 1%, by weight, sodium silicate.  
     
     
         52 . The aluminium substrate of  claim 45  comprising 0.1% and 1%, by weight, α-amino acid.  
     
     
         53 . The aluminium substrate of  claim 45  wherein said α-amino acid comprises at least one compound selected from a group consisting of aspartic acid, glutamic acid, lysine, tyrosine, threonine, glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptothan, serine, cysteine, asparginine, glutamine, arginine, histidine, and α-aminoadipic acid.  
     
     
         54 . The aluminium substrate of  claim 53  wherein said α-amino acid is selected from a group consisting of aspartic acid, glutamic acid, lysine, tyrosine and threonine.  
     
     
         55 . The aluminium substrate of  claim 54  wherein said α-amino acid is selected from a group consisting of aspartic acid and glutamic acid.  
     
     
         56 . The aluminium substrate of  claim 55  wherein said α-amino acid is aspartic acid.  
     
     
         57 . The aluminium substrate of  claim 45  wherein said α-amino acid has a solubility of at least 0.04 g/100 ml H 2 O at 25° C.  
     
     
         58 . The aluminium substrate of  claim 45  wherein said composition has a pH of at least about 6 to no more than about 7.  
     
     
         59 . The aluminium substrate of  claim 45  further comprising an α-hydroxy carboxylic acid.  
     
     
         60 . The aluminium substrate of  claim 59  wherein said α-hydroxy carboxylic acid is present at a concentration of no more than about 5%, by weight.  
     
     
         61 . The aluminium substrate of  claim 59  wherein said α-hydroxy carboxylic acid is selected from a group consisting of malic acid, tartartic acid and citric acid.  
     
     
         62 . The aluminium substrate of  claim 61  wherein said α-hydroxy carboxylic acid is tartartic acid.  
     
     
         63 . An electrolytic composition comprising 0.1% and 1%, by weight, sodium silicate and 0.1% and 1%, by weight, a compound selected from a group consisting aspartic acid and glutamic acid wherein said electrolytic solution is at a pH of about 5 to about 7.