After setting my first row of rivets through the skin, I decided to take a scotchbright pad and run it over the outside of the skin along the rivet line, to smooth everything out (so when i run my finger along the rivet line it feels even smoother). When I did this, it rubbed the goldish-colour coating off the flush heads of the rivets, leaving them silvery like the rest of the skin. Is this a no-no? Have I exposed these rivets to corrosion in the years before I get to the stage of painting?