Metal finishing Q&As since 1989

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Paint "Flakes Off" when tightening screw

August 13, 2009

Hi,

I really need some help on Paint flaking off and hope someone can advise me.

During the tightening of the screw, the Paint (PU) on the surface of the part around the screw hole will flake off when the screw is fully tighten.

This same PU paint is used on Aluminium & Electro-galvanized steel.

I have tried doing clear chromate before painting for aluminium and putting primer on the Electro-galvanized steel (both Aluminium & Electro-galvanized steel also went through basic degreasing).

Have anyone have similar problem before & have any proposal?

Thank you.

Bruce Kee
Buyer - Malaysia

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A guess. The screw is cutting its own threads and/or is disrupting the metal leading to flaking. Possibly the paint is too hard and possibly it is over cured.
You really need a paint expert to look at the paint and the screw processes.

James Watts
- Navarre, Florida
August 17, 2009

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I think James has hit the problem straight on. However, I don't think any coating would stand up to the gouging action of the screw head. So what would I do to minimise this?
I would investigate the use of thin plastic or felt washers to act as a protection barrier between coating and screw head. I would hope that the final tightening of the screw head would embed into the washer and not the coating.

Terry Hickling
Birmingham, United Kingdom
August 19, 2009