Applying Epoxy Silkscreen Over Powder

Question:

We have been diligently trying to find an effective way to apply a silkscreen epoxy over a powder coat finish. We have tried different inks, prep methodologies, heat settings, etc., all without success. To be acceptable, these (aluminum) parts must be able to pass a tape adhesion test, meaning the application of clear tape that is pulled off rapidly . Currently, about 40% of the time the silk screen comes off with the tape. Any suggestions? Also, could there be powder coat characteristics that are contributing to the problem? B. R.

Answer:

Yes, there are definitely powder coating characteristics that can be contributing to this problem. You should discuss, or better yet write a Powder Coating Material Specification, that not only informs them which mechanical and appearance properties you need, but also describes the silkscreen process that will be performed post cure. This is extremely important since most powder coating formulations have excellent solvent resistance, which means silkscreen ink resistance in this case. Therefore, your powder coating formulation may be incompatible with your silk-screening process. Furthermore, your powder formulator will also suggest a silkscreen ink that is compatible with the powder coating formulation. Silkscreening over a powder coated surface has been successfully accomplished by numerous companies, so I think that your problem can be solved easily with a powder coating formulation change.