Ask the Expert Question-and-Answer Archive

by Ron Joseph

December, 2008

Powder Coating Zinc Rich Epoxy

Q. To reach more than 1600 hours salt spray for outdoor substations,we have defined the following process:

1.Mechanical blasting specially on weld seams.
2.Six stage conversion coating(Spray zinc phosphate)
3.Preheating
4.Powder application (Zinc Rich Epoxy)
5.Baking to Gel
6.Polyester powder application.
7.Curing in baking oven.

Questions:

A. In essential when we are apply Zinc rich epoxy,we are looking for it,s sacrificatin property in galvanic corrosion so I think that the zinc phosphate layer will block this sacrification property of our zinc rich epoxy coating.
Is my Idea correct?
B.Is it possible to omit the chemical conversion coating process.

A. You should not go through the six stage zinc phosphate system AND apply zinc-rich primer. Since you require cathodic protection apply the zinc rich primer directly to the CLEAN abrasive blasted steel surface and omit the conversion coating process.

Regards,

Ron Joseph