Coating on No. 318's rods?

I was quite impressed with the cosmetic restoration done on No. 318 at the museum. Other engines should be so lucky. One question: the main and side rods had been polished and looked to be coated with a clear coating that appeared heavier than the normal sprays like Krylon. I'd like to know what the coating was and how it was applied. Automotive clear coat perhaps?

Three years ago, we spent most of a summer removing paint and polishing the rods and valve gear on our 4-6-0. We applied several coats of spray Krylon, but by next Spring they had rusted badly. We then had to treat the rust and apply Rustoleum primer and aluminum paint. Rust occasionally still pops through, which we treat with Rustoleum Rust Reformer, then repaint. Working locomotives generally had polished rods and motion work, thus I'd like to know more about the product used on D&RGW 318.