Metal finishing Q&As since 1989

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Paints won't adhere to chromated aluminum aerospace parts

After preparing our aluminum surface with (jet clean and Alumiprep 33 [on eBay or Amazon]) we proceed spraying Alodine 1200s treatment all over the surface and rinse it after 3 min. Then we painted with three different paint supplier, we found ourselves with paint adhesion problem. Many areas are chipping up to the skin surface and paint's flaking in fragile way.

We would like to know if our skin treatment can be defective and what is the specs. for water (ex: PH, temperature...) because we are suspecting water to be part of the problem.

Eric Galarneau
Aerospace - Mirabel, Quebec, Canada
2003

The MIL spec used to require a minimum of 24 hours from chromate to paint to allow the "jell" to appropriately dehydrate. Second, and not mentioned is the primer. Some paints will not work of chromated surfaces well enough for most purposes. Use a primer specifically designed for use on chromated parts.

James Watts
- Navarre, Florida
2003