Studies in the corrosion of metals occasioned by aqueous solutions of some surface‐active agents. I. Copper

The action of dilute aqueous solutions of representative anionic, cationic and non‐ionic wetting agents on sheet copper has been studied. Three types of water have been used—London tap‐water, distilled water and tap‐water softened by the zeolite base‐exchange process. The effects of varying the pH of the solutions from 2 to 12 and of temperature changes have been investigated. Most of the anion‐active agents examined first coated the copper with a water‐repellent film which afforded protection to the metal with primary and secondary sodium alkyl sulphates and sodium alkyl aryl sulphonate, but not with sulphonated castor oil or triethanolamine lauryl sulphate. With the cationic agents no water‐repellent film was formed and only triethanolamine attacked the copper to any great extent. There was no obvious action with the non‐ionic agent. In general, rise of temperature caused increased attack, but changes in pH of the solutions were without marked effect on the course of the corrosion. All results have been expressed graphically and a mechanism is suggested.