The US Navy does indeed experiment with different metal finishes on a wide variety of small arms used aboard ships during the late 1850's to early 1870's.
Tin plating seems to have offered the best results.
However, the Navy also found that by adding a dissimilar metal to the surface of the small arms in a salt air/water environment caused more problems with corrosion than it solved.
Armory Bright and Blued worked best.
My best,
Blair