I was sorting out the parts on my spare T/A motor and wondered about this rod. It is completely covered in a thin layer of copper. The motor had several failures in its short life. It had rods from two different engines and two new rods. One was normal but the other was completely covered in copper. Even the rods bolts and nuts wee covered. The bearing surface and bushing were clean. Any ideas? All I could figure out that it may have been to add a little weight to balance it. IDK. It blasted off for the most part in my glass bead cabinet.