Too Much Paint

Question:

I am an industrial paint salesman. One of my new customers wants to apply what I believe is too much paint on his product. The product is essentially a thin gage sheet metal cabinet. The structure will see lots of abuse from door slamming and flexing. Can you help me explain to him the problems he may be getting himself into by doing this? 

Answer:

Your customer must belong to the “The More the Better” society. Since his product will be abused, he feels that the more paint he applies the better it will hold up. Unfortunately that is not always true. Paints are engineering materials. They are designed to meet specific performance requirements at a specific film thickness. If paints are applied at too low a film thickness, corrosion protection and moisture resistance properties may not be met. If paints are applied at too high a film thickness, adhesion, flexibility and impact resistance properties may not be met.

At higher film thicknesses, it is possible that the forces of film cohesion can be greater than the forces of film adhesion. In the event of an impact or flexing of the substrate, the film can be delaminated from the substrate. This is a situation where too much of a good thing can become a bad thing.