Marine grade stainless alloys typically contain molybdenum to resist the corrosive effects of NaCl or salt in seawater. Concentrations of salt in seawater can vary, and splash zones can cause concentrations to increase dramatically from the spray and evaporation. SAE 316 stainless steel is a molybdenum-alloyed steel and is the second most common austenite stainless steel (after grade 304). It is the preferred steel for use in marine environments because of its greater resistance to pitting corrosion than other grades of steel without molybdenum. The fact that it is negligibly responsive to magnetic fields means that it can be used in applications where a non-magnetic metal is required. A fully austenitic grade (super austenitic, low magnetism), even when cold worked, is Nitronic 50. An example of a non-molybdenum grade performing well in seawater is Nitronic 60. "The pitting resistance of NITRONIC 60 in sea water is actually better than Type 316 due to the high levels of Si and N. The N also increases the yield strength..". While 316 is not completely rust-proof, the alloy is more corrosion-resistant than other common stainless steels. Surgical steel is made from subtypes of 316 stainless steel. In addition to molybdenum, 316 also contains a number of other elements in varying concentrations (see table below). Non-standard grades include 316H which has a "high" carbon content of greater than 0.04% giving it a high creep rupture strength at high temperatures, 316L(Hi)N which is an extra-high nitrogen grade (0.16-0.30%), 316Ti which is stabilized by titanium, 316Cb which is stabilized by niobium, 316L-SCQ which is a high-purity version of 316L, and 316LS which specially adapted for surgical implants.
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