The Mo-bearing Type 316 alloy on the other hand, will handle waters with up to about 2000 ppm chloride. Type 304 stainless steel is considered to resist pitting and crevice corrosion in waters containing up to about 100 ppm chloride. The PRE N of Type 316 and 316L (24.2) is better than that of Type 304 (PRE N=19.0), reflecting the better pitting resistance which Type 316 (or 316L) offers due to its Mo content. A relative measure of pitting resistance is given by the PREN (Pitting Resistance Equivalent, including Nitrogen) calculation, where PRE N = Cr+3.3Mo+16N.

Resistance of austenitic stainless steels to pitting and/or crevice corrosion in the presence of chloride or halide ions is enhanced by higher chromium (Cr), molybdenum (Mo), and nitrogen (N) content. In such media, Type 316L is preferred over Type 316 for the welded condition since low carbon levels enhance resistance to intergranular corrosion. A notable exception is in environments sufficiently corrosive to cause intergranular corrosion of welds and heat-affected zones on susceptible alloys. Generally, the Type 316 grade can be considered to perform equally well for a given environment. This is a factor in the manufacture and handling of certain food and pharmaceutical products where the molybdenum-containing stainless steels are often required in order to minimize metallic contamination.

It is widely used in handling hot organic and fatty acids. This alloy offers excellent resistance to boiling 20% phosphoric acid. The molybdenum-bearing Type 316 stainless steel also provides resistance to a wide variety of other environments. In such applications, however, the acid concentration has marked influence on the rate of attack and should be carefully determined. Where condensation of sulfur-bearing gases occurs, these alloys are much more resistant than other types of stainless steels. Service tests are usually desirable as operating conditions and acid contaminants may significantly affect corrosion rate. At temperatures under 100° F (38° C), this type has excellent resistance to higher concentrations. At temperature as high as 120° F (49° C), Type 316 is resistant to concentrations of this acid up to 5 percent. Type 316 is considerably more resistant than any of the other chromium-nickel types to solutions of sulfuric acid. One known exception is highly oxidizing acids such as nitric acid to which the molybdenum-bearing stainless steels are less resistant. In general, media that do not corrode 18-8 stainless steels will not attack these molybdenum-containing grades. Types 316 and 316L are more resistant to atmospheric and other mild types of corrosion than the 18-8 stainless steels. In addition to excellent corrosion resistance and strength properties, Types 316 and 316L alloys also provide the excellent fabricability and formability which are typical of the austenitic stainless steels.

Types 316 and 316L generally contain 2 to 3% molybdenum for improved corrosion resistance. These alloys also offer higher creep, stress-to-rupture and tensile strength at elevated temperature. Types 316 and 316L are molybdenum-bearing austenitic stainless steel which are more resistant to general corrosion and pitting/crevice corrosion than the conventional chromium nickel austenitic stainless steel such as Type 304.

316 sheet metal