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Passivation on aluminum castings

Is it necessary to do passivation ( Cr or Zr ) during pre treatment of aluminum castings for painting , when we are using 3~4 DM water rinses after de greasing and later on applying anti-corrosive primer before painting?

NAVEEN SHARMA
AUTOMOTIVE - GURGAON , Haryana , INDIA
2007

That ALL depends on what quality of a job you desire. A chromate conversion coating is optimum (price vs adhesion) Zinc phosphate and anodize are two other options for pre paint.
Some primers do not like chromate, so check with your prime MFG before you use it.

James Watts
- Navarre, Florida
2007

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