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Passivation of carbon steel

2007

Before the painting process of carbon steel metal, we dip the metal into HCl solutiuon and then perform hot phosphating on it. After that our customer want us to do passivation before going into paint process. Please explain.

Regards,

Kamaljit Singh
fabrication - Ludhiana, Punjab, INDIA

2007

"Passivation" means different things in different circumstances, Kamalit. When one is speaking of zinc plated surfaces, 'passivation' means chromate conversion coating. When one is speaking of stainless steel surfaces, 'passivation' means a chromium enrichment and controlled oxidation process based on nitric or citric acid .

But when one is speaking of steel surfaces, the term is ambiguous or undefined. Your customer may be wanting you to dip the parts in a chrome-bearing final rinse or deionized water after phosphatizing, or he may just be asking for phosphatizing, but it requires clarification.

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

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