Q. We need some reasonable corrosion protection for out parts, and our powder coating is failing in salt spray testing after nearly 300 hours. What should we change to enhance our salt spray results? B.P.
A. First, let’s be clear on the difference between salt spray results and corrosion resistance in field use. Salt spray is a measurement of how well the coating holds up in a salt spray cabinet. It cannot predict the real resistance to a particular environment. It is useful for comparison of different treatment and coating options, but it does not predict field life. If you need to understand the potential field life you should use some type of cyclic testing.
When a coating does not have good resistance in a corrosion test it can be from several different causes:
If you have a satisfactory cleaning and pretreatment setup, a good powder, and good coverage at the necessary thickness you should be able to meet your salt spray requirements.