Letter 22036

Sulfuric Acid coagulation issue  

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Our continuous anodizing line comprised of ususally 20-25% tech. grade Sulfuric Acid has had recent issues of coagulation when either the concentration spikes (25-30% sulfuric) or if ambient temp. drops below 70 degrees. The soultion turns a iridescent pearl color and looks of oil. Can anyone explain the reason? Solids form at the bottom of the tank and only water or elevated temp. will break it.???

Jason Von Marschner
- Ontario, CA, USA

I'm having a bit of a hard time picturing it, but it sound like you have too much aluminum in the bath and it is precipitating. Decant those solids out of the solution.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Running at 25-30% acid is in my opinion very high. It may be that way because you have a very high Aluminum content. Check the aluminum content out and if it is over 12oz per gal decant. Also check for copper.

Drew Nosti, CEF Ladson, SC

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