Coating Failure in Marine Environment

Q. My company is a building contractor that has supplied powder coated aluminum gutters and downpipes, as well as powder coated steel handrails to a building situated in an exposed marine environment. The items have been exposed to the elements for approximately 18 to 24 months, and the powder coating is starting to break down and lose adhesion is some areas. Can you give us any advice or information on why the coating is beginning to fail? —G.B.

A. A seacoast environment is one of the toughest challenges to the integrity of any coating. There could be several reasons why the material is failing so soon. It starts with the metal preparation. Aluminum needs to have a strong conversion coating using a reliable chrome or non-chrome product. If the surface is treated right, the powder will adhere and you have a fighting chance against the harshness of the salt-laden air. Secondly, the surface will need a high-quality primer to protect against corrosion and provide a good bond for the topcoat. The topcoat material needs to be a good quality also to hold up against sun and rain. The overall thickness must be adequate to resist penetration to the substrate. The coating has to be applied correctly and cured correctly. One or more of these things was not done correctly in your case. It is possible the surface was not treated correctly. The coating may be one coat, or it may be too thin. The coating selected may be right for the environment or it may not have been cured correctly.