We design and fabricate aluminum exhibits and have used the same company for all our powder coating needs, mostly aluminum. Until lately I had always assumed that some sort of acid etch bath was part of the pre-clean process before the powder coating process. Our powder coater now wants to charge us extra for a process of cleaning that would remove the name brand printed on the aluminum stock claiming that it will bleed through the white finish powder coat necessitating us washing down the parts with solvent before they go out. Does this makes sense? A.M.
It is usually a good idea to clean something prior to powder coating it, although it is not an absolute necessity, depending on the conditions the material sees prior to coating. The aluminum generally comes in with a good, clean finish. If it goes though a fairly simple fabricating process with no additional lubricant application (i.e. just shearing), it may be possible to go directly to painting. Even if the metalforming process is more severe, requiring the application of lubricants, it is possible they have been cleaning the residual lubricant from the surface, but the cleaner may only be a mild detergent that would remove the lubricant, but maybe not the mill printing.
It sounds like something has changed in the process. Is the application of the white powder coat new? If white is a new color, it is true that it would have a more difficult time hiding the printing than a darker color. The print would not actually bleed through and could not be removed by solvent wiping, but if the white powder is applied at a low enough coating thickness, it may be possible to see a dark printing under it.
So to answer your question, it does not sound like they are trying to cheat you, but it could be a simple misunderstanding of what they currently do for you. It would be worth asking them for a process flow diagram of the current process that they have used to this point and the new one they propose. That should easily highlight the differences and you can use that to get answers to your specific questions. In the end, I would think they would be able to provide you “with” and “without” samples of the white powder over the printing.