Letter 3065

Low Chrome Seal For Anodized Aluminum 

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I am interested in a "low chrome" 125 ppm dichromate seal for anodized aluminum. Where might I find technical information on this process? Is such a seal formulation proprietary or patented?

Steven Hendricks
- Fort Worth, Texas

The aerospace industry uses such a seal and it is not proprietary. The seal composition is contained in Boeing and Mac specs., BAC5019 Chromic Acid Anodize, but the solution is made up and maintained to the following limits: Hex chrome 45-100ppm as Cr+6, pH 3.2-3.8, Silicates 10ppm max., TDS max., 250ppm. The temp used for processing depends upon if the low voltage(22v) or high(40v) voltage process is used.The makeup is 26g/100gal chromic acid with 18g/100gal sodium chromate using DI water.

Ward Barcafer CEF
- Wichita, KS

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