Q. We refinish metal cannery machine parts. The paint must be abrasion-resistant and withstand daily high-pressure washings of 1,000 psi. Where the coating has been damaged, there is often severe rusting. We then remove the rust and all the old paint on the parts by sandblasting to bare metal. We apply a wash primer and then a two-part epoxy topcoat. Is this the best method? M.J.
A. In general, I like your approach to the refinishing problem: sandblast, wash primer and topcoat using a two-part epoxy enamel. However, I suggest you modify your finish system by replacing the wash primer with a two-part epoxy primer because of its superior corrosion resistance. I also suggest you replace the epoxy enamel with a two-part polyurethane because of its superior abrasion resistance. My recommended finish system is:
1) Sandblast to white metal in accordance with SSPC-SP5 White Metal Blast Cleaning.
2) Prime with a two-part epoxy primer at a dry film thickness of 1 mil.
3) Topcoat with a two-part polyurethane enamel at a dry film thickness of 2 mils.