Dry That Primer

Q. We are trying a new system to paint steel parts in our paint booth. This involves priming the parts, then painting them as soon as possible in the next section of the booth. We are having problems with getting the primer dry before the paint goes on. Our products are large steel welded assemblies. We are looking at the amount of primer we use, the type of primer, any additives and the temperature of the booth and the parts. Do you have some insight into this problem? J. F.

A. My eyesight isn’t as good as it used to be, but my insight is still 20/20. There are certain things in life that can’t be rushed and one of them is paint drying. I know, watching paint dry is boring. Actually the operative word is not drying, it is curing. The primer must be cured before topcoating. Otherwise, there could be big problems. For example, topcoating over uncured primer could cause adhesion problems.

There are steps you can take to accelerate cure time. (It is important that any of these be done in compliance with all environmental, fire protection and worker safety regulations.) 1) You can change to a fast drying primer. 2) You can change your solvent blend to one that is faster drying. 3) You can use Infrared radiation to accelerate curing. 4) You can blow heated air over the parts. 5) You can apply only enough primer to provide corrosion protection to the parts (thick coatings often take longer to dry). These suggestions will give a starting point to help solve the problem. Remember, that any change must be in compliance with regulations.