Stainless steel is used extensively throughout industry for both original equipment manufacture as well as for replacement. Incases where a joint is designed to be taken apart and reassembled, the corrosion resistance of the fastener is particularly important so that corrosion will in no way hamper or prevent its removal. The cost of removing rusty bolts, and replacing them with new ones, is more expensive than using corrosion resistant fasteners to begin with. Additionally, many designers consider the extra coat of stainless steel fasteners as inexpensive insurance against possible failure or loss of aesthetic appeal.
The austenitic (300 series) stainless steels are characterized as having excellent corrosion resistance. Chromium is the element that provides the stainless steel with its "stainless" name. These specifications cover the 300 series stainless steels, all of which are essentially 18-8 (18% chromium and 8% nickel) materials, with compositions very close to the nominal composition for Type 304. If an application calls for a material with corrosion resistant properties better than that of Type 304, Type 316 is the next logical candidate. Type 316 stainless steel is a higher alloyed material containing 2-3% molybdenum, which provides pitting and crevice corrosion-resistant properties, especially in environments containing chlorides.