Thickness of Metal Affecting the Coating Process

Q. I am a newcomer to powder coating and have a question for you. When powder coating mild steel, will the thickness of the mild steel itself, say 25 mm (one inch) or more, have an effect on any stages of the process or the final result? In a nutshell, should I or shouldn’t I powder coat very thick mild steel? N. H.

A. There are several concerns I have when you powder coat a product that is made from thick steel, as is the case here. First of all, most steel plate provided this thick is hot rolled grade. As such, it has heat scale on the surface that must be removed by pickling, grit blasting or sanding/wire brushing. If you do not remove all the scale before applying the powder coating, you will have poor adhesion to the steel substrate and the coating will most likely flake-off in relatively short order.

The only other issue I can think of could be a problem powder coating one-inch thick steel is the oven dwell time to cure the powder. The mass of such a thick steel plate will require a prolonged bring-up time to heat the part to the desired metal temperature to cure the powder. Expect a total oven dwell time to be substantially longer than lighter gage steel products you normally coat.