Tried a simple unscientific yet interesting test of "rust prevention" sprays. After moving several hundred large round bales of hay, my carbon steel hay spears are bright polished. They will rust overnight it seems after use. After the spring hay season, I tried RemOil rust preventor, CLP, Kroil (not really advertised as a rust preventor), Miltec greese, Hoppes elite, shooters choice gun oil, and WD40 Specialists corrosion inhibitor. All have rusted but the WD40 Specialist - to this day (3 months) while exposed to dew, rain, sun etc. it has not allowed the polished steel to rust. Its going on all my guns!