You failed to mention what kind of rivets you are trying to protect. Copper, Brass, Nickel over Brass, Steel, Stainless Steel or other????? Copper and Brass will patina naturally, and in addition Copper when exposed to even light oil, moisture or even just air will over a very long period, develop the green Verdigris which is pure hell to clean off of leather. Frequent wiping (once a month or more) will probably eliminate the formation of the Verdigris. Need more information from you to be of any more help.
Paul