Letter 9036

Salt Spray Resistant Water Based Paint Needed For Springs

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Our company makes mild steel springs which must pass a 36 hour salt spray test ASTM B-117 [link is to spec at TechStreet]. We are looking for a water based paint in which the springs can fall into for coating. The parts leaving the manufacturing process at about 550F are immediately immersed in the paint. Paints we have used so far fail after about 5 hours. Does anyone know of something that might work?

Thanks,

Chris Ballew
- Newport, TN

The problem isn't the paint, it's the lack of a pretreatment system. Consequently, I don't think you'll fix it with a different water-based paint. A simple iron phosphatizing step followed by a rinse and the paint would probably work fine.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

You don't mention a color preference, but many springs are finished in a black oxide finish with an oil rust prevent applied as an after finish. Passing a 36 hour salt spray test is an easy requirement for a decent oil - we often see in excess of 80 -90 hrs. Also, with black oxide the possibility of hydrogen embrittlement from the phosphate step is eliminated (you don't say the hardness of the springs, so I'm assuming).

Dan Brewer
chemical process supplier - Gurnee, Illinois

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