This is my first post in this forum and am not sure if this is the right group for this query.
If not request the admin to kindly move to the correct group.

We are facing a problem after painting of SS321 equipment. SA-240 TP 321 plate (Thk 6mm and 8mm) was cold rolled to make the shell of the equipment. The DFT measurement after painting showed a higher reading. On scrutiny we found that the bare plate surface itself shows DFT varying from 100-160 micron. We are in consultation with experts from painting, NDT, Testing, Metallurgy but everyone is surprised with this finding and unable to explain this phenomena. Consequently we are unable to measure the correct paint thickness because the bare plate DFT reading gets added to paint thickness. If anyone has faced this or is aware of the solution kindly do let me know.

Thanks and regards

Jaggu