Ask the Expert Question-and-Answer Archive

by Ron Joseph

Mill Paint

Q: We have a few mills (cnc) that the coolant eats the paint. I was wondering if you could make a suggestion as to what paint/primer would work the best in the long run. The coolant is a fully synthetic or a soluble oil. (Q lube or hangstefers s500cf) The base metal is cast iron. I thank you for your time and knowledge.

A: Off-hand I'm not familiar with the coolant you use; therefore I don't know how corrosive it is to the paint. Generally, I believe that polyurethanes that comprise a polyester base (Component A) and polydiisocyanate curing agent (Component B) should do the trick. Please bear in mind that Component A should preferably not be an acrylic, since polyesters are proven for chemical resistance. The aerospace industry uses epoxy and polyurethane coating systems that must withstand Skydrol, a corrosive hydraulic fluid. The Air Force applies MIL-P-53022 or MIL-P-23377 epoxy primer under MIL-C-83286 polyurethane top coat, and it is entirely possible that the same system will withstand the corrosion of your lubricant. You might like to experiment with this system.

Good luck,

Ron Joseph