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Dehumidification an answer for clearcoating bare mild steel?

We have constant call for bare metals with a clear topcoat finish in our area of work. Typically, we do everything within our power to clean and degrease the metal prior to coating it, and our experience to date has been entirely hit or miss. Sometimes it works well, sometimes we need to strip and recoat the metal almost immediately. I am wondering what effect extreme dehumidification would have on our process. We are doing several projects in Las Vegas over the next year to two years, and feel that the dry air there will allow our finish a level of permanance. The problem would be on our end, where the humidity is significantly higher than the desert air of Nevada. If we can get the humidity levels in our finishing room down to the levels found in Nevada, is it possible to prevent moisture from becoming trapped under the finish? Has anyone tried a similar experiment? Any thoughts would be appreciated.

Jason West
Architectural metalworking company owner - Stamford, CT, United States
2007

Hello, Jason

There is a reason why auto manufacturers use galvanneal rather than plain steel in corrosion-prone areas of the car . . . and a reason that they then phosphatize it . . . and a reason that they then electrocoat prime it . . . all before finish coating and clear coating. And the reason is, of course, that every step on the list improves corrosion resistance, and any step omitted decreases corrosion resistance.

Clear coating plain steel can be "hit or miss" because the approach requires abandoning most of the proven corrosion fighting tools. I don't think humidity control will be as effective as applying that money towards a clear electrophoretic lacquer as a basecoat, followed by the conventional clearcoat. But this is just a personal theory.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007