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Olive drab (green) passivation of aluminium alloy items

Can someone let me know the correct process and composition of the olive drab (green) passivation required to be done on aluminium alloy die-casted components.

U K SINGHAL
- New Delhi, (India)

Can someone please let me know the process of obtaining green passivation on steel / sheet metal parts. I would be grateful if one can share the chemical compositions also.

Mukesh Tiwari
- Indore, India

Mr. Tiwari,

Green passivation is not done directly on steel, it is done on zinc plated steel. The process will not react with steel, only lighter, more active metals like aluminum, cadmium, and zinc. The formulations of practical passivating solutions are trade secrets, developed after years of research, but in general terms they are composed of chromic acid, sulfuric acid, and smaller amounts of various accelerants and stabilizers.

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

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