W ear, zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 44 (1977) 145 - 162 0 Elsevier Sequoia S.A., Lausanne - Printed in the Netherlands 145 zyxwvutsrq CHEMICAL EFFECTS IN SLIDING WEAR OF ALUMINUM* MING-KAI TSE and NAM P. SUH Department of M echanical Engineering, Massachusetts Institute of Technology, Cambridge, Mass. 02139 (U.S.A.) (Received May 18, 1977) Summary The mechanism of the sliding wear of metals in corrosive media was in- vestigated. In particular, the role of chemical heterogeneities on chemical interactions between the sliding surface and its environment was studied using 2024 aluminum alloy and sodium chloride solutions of varying pH and NaCl concentration. Sliding wear tests with a cylinder-on-cylinder geom- etry were performed at a sliding speed of 1 m min-’ and a normal load of 9.8 N (1 kgf). The results show that at pH = 0 and pH = 14, the wear rate is dominated by the dissolution of aluminum into the NaCl solution. In the intermediate pH range, the wear rate is shown to be controlled by the con- joint actions of corrosion and delamination wear. Microscope examination of the worn specimens by means of a scanning electron microscope further confirms that the mode of corrosion is of a localized nature. Introduction The sliding wear of metals is generally controlled by material properties, loading conditions and environment. The preceding papers [l - lo] on the delamination theory of wear have covered various theoretical and practical aspects of the first two controlling factors, i.e. material properties and load- ing conditions. The purpose of this paper is to present the work done on the effect of any chemical interaction of the sliding surfaces with the environment, The mode of wear under this condition is commonly referred to as corrosive wear. Chemical effects on the sliding wear of metals are important in many practical situations. Examples are boundary and extreme pressure (EP) lubrication of sliding surfaces, which is often considered as a form of con- trolled corrosive wear, and lubrication and wear of machinery in a marine environment, in which salt water and salt-bearing air provide a corrosive *This paper was added to this series after the paper “An overview of the delamination theory of wear” [ 1] was accepted for publication.