How to insure freedom from residue after paint stripping

I would like to know if anybody test production parts returned from paint stripping for "surface free from residue"

Usually the stripping process has an established duration based on experimental run. What if coating thickness is higher and some residue is still on the surface?Non visible ,but thick enough at some spots to damage adhesion?

What stripping process is safer for aluminum parts quality?
chemical with risk of residual coating left
plastic -with risk of plastic mechanical attachment to surface and possibility of residual coating left
steel - deposit of Fe and all the above
stainless - with residual coatings remaining.

First a quick answer to one part of the question. Paint thickness impacts most removal methods negatively. That is, it takes longer/more energy to remove more paint. The one exception to this may be molten salts. Molten salt has so much excess energy, both heat and chemical, that almost nothing can resist its powers.

Now onto the other questions... Residue is such a open issue. There are lots of residues that can cause future paint adhesion failure in repainting stripped parts that I can't go into it here. Just a few categories to get you started: residual paint film, residue from the stripping compound itself, and rinse water quality problems.

Mechanical methods can get around some of these questions, but are not always the most cost effective way to remove coatings due to their labor intensive natures. However, they do have a place in this discussion and work well.

Another point, is the pretreatment sequence on these "repaints" adequate to provide for the removal of the residues on the "repaints" or are they just passed through the same pretreatment as "new" parts. Sometimes we must consider that we live in the real world and not in a "residue-free" world where everything works out perfectly. Such is the world of paint removal.

Good Luck with your problem...