Salt Spray Resistant Water Based Paint Needed For Springs
Q. Our company makes mild steel springs which must pass a 36 hour salt spray test ASTM B117 [link by ed. to spec at TechStreet] . We are looking for a water based paint into which the springs can fall for coating. The parts leaving the manufacturing process at about 550 °F 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?
- Newport, Tennessee
A. Hi Chris. The problem isn't the paint, it's the lack of a pretreatment system in my opinion. 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. RET
Pine Beach, New Jersey
A. 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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