Bought an Arsenal mold from another member here 5 cavity .360 155 gr rnfp. Did some casting with it and after the mold cooled I noticed the sprue plate looked like some lead had stuck to it so I used a little Hoppe's on a rag to clean it and the black coating started to come off. Anyone else ever have this happen and what did you do to keep the steel from rusting cold blue,heat resistent paint or some other type of coating. I have other aluminium molds and never had the finish come off the sprue.