Corrosion by Acids at High Temperatures

A test method is described for obtaining corrosion data with acids and other corrosives at temperatures above their normal boiling points. The method, which has features of simplicity and general usefulness, involves use of a flame-sealed heavy-wall glass tube as container for the metal specimen and corrosive fluid. The atmosphere over the fluid can be controlled and, by evacuating the tube before sealing, can be made to consist only of the equilibrium vapor at test temperature. It is estimated that the tubes withstand gas pressures up to about 1000 psig which corresponds to a test temperature of 285 degrees C for water. Appropriate test safeguards are described. Corrosion data obtained by this method are presented for various alloys exposed to sulfuric acid, phosphoric acid, nitric acid, formic acid, boric acid and phenol at different temperatures and concentrations. An interesting general observation from these corrosion data is the relatively good corrosion resistance of copper in sulfuric, phosphoric, boric and formic acid solutions.