Powder coating all the same?

Had my bumpers powder coated by one shop and my fenders done by a different one. The bumpers seem to have a nice thick coating and have held up quite well. The fenders seem to have a thinner coating and look like crap. Bumpers are steel and the fenders aluminum. I was always under the impression powder coating is powder coating. Is there a difference? Thanks..

I have had a similar experience. Had my aluminum fenders done by one company which turned out great and my steel rock rails done by another which hasn't held up to well. It must have to do with the different methods of each company. I don't think steel vs aluminum has anything to do with it