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Bonding to Nitrided Surface

I am looking for a corrosion resistant coating for custom fasteners that needs to be later bonded-to with a rubberized epoxy coating. This is for a sub-sea application subject to fatigue loading.

I'm considering Zinc phosphate, which is offered by my fastener vendor, which I understand is commonly used as a primer, but I know that phosphate coatings do not offer the greatest corrosion resistance.

What about QPQ? The surface coating is low friction, which usually means poor adhesion, but is there another primer that can go between the QPQ and the Epoxy?

Mike Orlet
Product Design Engineer - Horsham, Pennsylvania, USA
August 12, 2010

In my understanding "QPQ" Quench + Polish + Quench, this is Salt Bath Nitriding + Oxidation.

After QPQ, surface finish is very smooth, better you do the Epoxy after 1st Quench. after the 1st quench the surface are slightly porous, epoxy will deposit very easily.

Kannan B
- Salem, TamilNadu, India
August 16, 2010

Dear Mike Orlet,

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