The Behavior of The Chromium Nickel Stainless Steels In Sulfuric Acid^⋆ Available to Purchase

This article shows the corrosion rate of four commercial types of chromium nickel stainless steels and one special type in sulphuric acid of varying concentration from 0 to 95 percent, at four temperatures, 100° F (38° C), 150° F (65° C), 175° F (80° C), 200° F (93° C). The effect of additions of various sulphates and oxidizing agents to the acid on the corrosion rates is also shown. All samples were tested in an activated state and the data indicate the acid concentration and temperature, in which the metal becomes and remains passive. At temperatures about 150° F (65° C), all of the steels remain active in practically all acid concentrations and corrosion rates are high. Below this temperature, the molybdenum bearing steels, Types 316 and 317, are most resistant and increasing chromium content, Type 310, has some effect in lowering the corrosion rate. The addition of copper to the molybdenum bearing steels improves resistance to a marked degree, although these steels appear to behave similarly to copper and copper-nickel alloys in that they do not show a sharp passive-active boundary. The addition of various inorganic sulphates to sulphuric acid causes a marked lowering of corrosion rates. There is an indication that sulphates of metals below chromium in the E. M. F. series completely inhibit attack and provide a passive condition. The addition of oxidizing agents, such as nitric or chromic acid and dichromates also completely inhibits attack.