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Alodine required after powder coating?

2001

I have multiple aluminum parts where the final product will have some surfaces powder coated while the remaining areas are just coated with an Alodine/Chromate conversion process. We apply the Alodine/chromate to the parts prior to powder coating to ensure good powder adhesion. However, because of the high temperatures the parts see during the powder coat process, our chemists have told us we have compromised the corrosion resistant properties of the Alodine/chromated surfaces and we need to reapply the Alodine/chromate to those otherwise bare surfaces (2 powder coats being applied (a color + a clear top coat) at ~ 375 deg x ~ 20 minutes).

We are not experiencing any problems with the reapplication or with our final products but would like to know if this reapplication is necessary, how this is generally handled in the powder coat industry, and if there are any other general concerns we should have with this process.

Thanks,

Beth Connors
Sandia National Laboratories - Albuquerque, New Mexico, USA

Yes, the powder coating bake has damaged the chromate and re-processing is the only way to get the chromate protection back to standard.

Don Brenner
- Lake Buena Vista, Florida, USA
2001