Zinc-plated steel is a low carbon steel for general use. Relatively inexpensive, with the zinc plating providing moderate corrosion resistance suitable for indoors or otherwise dry conditions. Color is either a blue-ish tint or yellow depending on the exact process. Hot-dipped galvanized steel has a thicker zinc corrosion resistance. coating for better making it suitable for outdoor use. Because of the thick plating, only galvanized nuts and washers will fit galvanized bolts. The coating typically has a rough, dull grey finish. Alloy steel is highly A. hardened and usually black oxide and/or oil coated, offering little corrosion resistance