These stretch formed aluminum skins on a V2500 translating cowl inner panel have this odd pattern. It was first written up as corrosion, except we have seen the pattern on the same area of multiple panels and it doesn't seem to be corrosion. The primer is adhering well an where the primer was removed using a chemical stripper it has a nice golden color of a chemical conversion coated surface. Could this pattern have been caused by forming? I've never seen it before. See pictures in the attached word document.
Remember, first define the problem, then solve it.