“We are preparing to coat 2B stainless steel with a polyester powder. The final product will be an outdoor constant temperature device. Our pretreatment is one stage wash/phosphate and two rinse stages. The parts are then run through a dry off oven before coating. Should we expect any adhesion problems? Will this finish stand up to various weather conditions? Is there an alternative to stainless?”
“Stainless steel is very difficult to coat without adhesion problems. The iron phosphate will do little to prepare this surface for adhesion.
Pretreatment for stainless steel is focused towards adhesion, since corrosion resistance is not a problem with this substrate. You should review your requirements with your chemical supplier and ask for his recommendations.
Changing the substrate to galvannealed steel can provide for better adhesion; however, it will not perform as well with corrosion. Review your performance requirements carefully before you select a substrate material.”