Metal sweating

I currently powder a large steel piece. It has multiple welds both front and rear. I normally 120 grit blast for prep. I then spray a zinc rich primer with a black top coat. I had always sprayed the primer on cold and then applied the black after a partial cure of the primer. Today I was running a load and did not have the primer ready so I push the first load in to pre-heat while I set up the gun.

When I pulled them out to spray the primer the parts were sweating along the front face. There was so much moisture coming out them in places that it was dripping on the floor. I pushed them back in for 20-25 mins and it basically dried them out. All 5 loads did this, some worse than others.

Question 1 - What causes the steel to do this and is there a way to stop it during fabrication?

Question 2 - I have coated these same items for almost a year. What kind of problems would the moisture cause in the primer. Should I be worried about poor adhesion to the base metal and/or the top coat?

Tom

Last edited by DCInc (02/05/2009 - 01:18 AM)