I am ordering up AN bolts forvarious fittings throughout the plane. On the wings, we have some aluminum angle brackets that attach the butt ribs mounted over 4130 wing attachment fittings and using the same bolts for mounting. I have a feeling these should be stainless AN bolts instead of Cadmium plated for corrosion reasons. Is this correct? I am wondering if there is a need to isolate the aluminum from the 4130 with anything more than epoxy paint as well?