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topic 10121

Preventing corrosion with PVD film


Q. Hello,

I am neither familiar with PVD coating nor understanding the mechanism of corrosion. Now I am considering using PVD thinfilm as protective coating in an aluminium fan blower casing working in corrosive environment. Besides, I would like to have a Teflon coating added to the PVD film to enhance the anti-corrosion function.

Am I going in the right way of preventing corrosion?

Yang, Ning
- Hsinchu, Taiwan, ROC


 

A. The standard method of achieving high corrosion resistance using PVD is Ion Vapor Deposition (IVD) of pure aluminum. For maximum effect, after the coating is deposited it is glass bead peened (for densification and as to test the coating adhesion) then a chromate conversion coating added. In salt spray tests, very substantial lifetimes are achieved, even if the surface is scratched. The chromate conversion coating makes a big difference. I don't know what teflon will do, but it is difficult, if not impossible, to deposit by PVD.

jim treglio portrait
Jim Treglio
- Vista, California


 

A. Dear Mr. Yang Ning:

I have little experience with PVD coatings (I tend to believe they are too thin to protect and not good candidates to receive a plastic coating on top). But I've seen that aluminum is well protected from corrosion by a film of E-N (electroless-nickel). Depending on environment it can go from less than 0.001" up to 0.004" or more thick). It will cover uniformly, thus keeping the necessary balance for a rotating item such as a fan. Unfortunately EN is also not a good candidate for teflon coating, only teflon particle co-deposition but this is done for other purposes not to increase corrosion resistance.

Good luck,

Guillermo Marrufo
Monterrey, NL, Mexico



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