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Ted Mooney, P.E. RET
Pine Beach, NJ

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Aluminum bright dipping: Life of Phosphoric acid bath

Q. What is lifetime of phosphoric acid bath used for pretreatment aluminium before anodizing? ie; how much aluminium in units of weight, area, or based on properties of phosphoric acid?

Linson Chungath
hobbyist - Trichur, Kerala, India
2004

A. Sorry, I'm not familiar with such a pretreatment. Where in the process does this fit--as an acid cleaner? Are you referring to an aluminum bright dipping solution?

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

Q. I thank you for the technical word bright dipping. So I repeat the question--what is the lifetime of phosphoric acid bath used for aluminium bright dipping? ie; how much aluminium in units of weight, area, or, based on properties of acid.(maintainance of the bath).

Thank you

LINSON CHUNGATH
HOBBYIST - TRICHUR, KERALA, INDIA
2004

A. ASM Metals Handbook, Vol. 5, Surface Cleaning Finishing & Coating implies that dragout is the biggest factor in exhaustion of the solution and that the baths are quite tolerant of impurities. It says aluminum phosphate should be held near the tolerable limit of 10 to 12 percent, with a dissolved aluminum content of about 40 g/L.

The Surface Treatment and Finishing of Aluminum and its Alloys again implies that phosphoric nitric baths can, under good conditions, be controlled through dragin/dragout in a "never dump" scenario.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

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