Stainless steel does not readily corrode, rust or stain with water as ordinary steel does. However, it is not fully stain-proof in low-oxygen, high-salinity, or poor air-circulation environments. There are various grades and surface finishes of stainless steel to suit the environment the alloy must endure. Stainless steel is used where both the properties of steel and corrosion resistance are required.

Stainless steel differs from carbon steel by the amount of chromium present. Unprotected carbon steel rusts readily when exposed to air and moisture. This iron oxide film (the rust) is active and accelerates corrosion by forming more iron oxide, because of the greater volume of the iron oxide, this tends to flake and fall away. Stainless steels contain sufficient chromium to form a passive film of chromium oxide, which prevents further surface corrosion by blocking oxygen diffusion to the steel surface and blocks corrosion from spreading into the metal's internal structure.

Marine grade stainless #316 is the grade APAC fabricate with, or SAE 316 stainless steel. This is a molybdenum-alloyed steel and is the second most common 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. 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. In addition to molybdenum, #316 also contains a number of other elements in varying concentrations. Like other grades of stainless steel, marine grade stainless steel is a relatively poor conductor of both heat and of electricity when compared to metals and other conductive materials.

While 316 is not completely rust-proof, the alloy is more corrosion-resistant than other common stainless steels. Surgical steel is made from sub types of 316 stainless steel.
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.