plating, anodizing, & finishing Q&As since 1989
'Flash Attack' of series 300 Stainless Steels During Passivation
Passivation Of 300 Series Stainless Steels. It is widely quoted in the literature that 'flash attack' of stainless steels can occur during passivation (Metals Handbook, 9th Edition, V13 - Corrosion, p552). The phenomenon manifests as a dull grey surface finish. It is frequently quoted to be associated with increasing levels of chloride ions in the passivating bath (Terry DeBold, Machine & Tool BLUE BOOK, Nov 1986, pp74-77). It is suggested that a chloride level in access of 200 ppm causes the flask attack. Is there any other technical investigations reported in the literature regarding details such as the influence of temperature, acid concentration, chloride contamination, composition of the flash on the surface of the stainless steel, thickness, adhesion, and removal of the flash attack ?
It appears that everyone is aware of the phenomenon, but technical details are lacking. I very much look forward to any comments or discussion on this matter. Thank you.Dr Praful P. Patel
metallurgical - Sauk Rapids, Minnesota
Hi, Dr. Patel. We have a Passivation FAQ on line which discusses this issue. The best theory I have heard, which is discussed in the FAQ, is that the problem is caused by the formation of organic acids, and can be solved by truly extensive cleaning before passivation.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 27, 2009
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