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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Pitting occurs in the rinse after de-smut
May 16, 2011
Recently we have been experiencing pitting after anodizing process.We have done our analysis and found most of the pitting occur after the rinse tank immediately after desmut tank.We have changed a new water and added nitric acid to the bath but still have the pitting ocassionally. What could be the cause and how to remove permanently? What is the chloride content acceptable in the rinse and desmut tank?
Regards
Hanif
press metal - Klang, Selangor, Malaysia
Tell us the formula of the deox. Chloride seems to be your problem. Limits have not been published. I say under 50 ppm. However, how long are you staying in the acidic rinse water, what is the turn over, is there a galvanic voltage between the titanium rack and the stainless steel acid laden rinse tank?? There should always be two rinses between deox and anodize
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
May 19, 2011
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