Wear of iron and nickel in corrosive liquid environments
Friction and wear behavior of Fe and Ni sliding on aluminum oxide in aerated sulfuric acid and hydrochloric acid were investigated. The results show that the concentration of acid is an important factor in controlling the metal loss caused by wear corrosion processes in the acids. At very dilute acid concentration (10 to the -4 N), Fe behaves differently from Ni. Fe develops a soft, friable deposit, while Ni develops no corrosion layer. The formation and removal of the corrosion deposit on Fe resulted in high metal loss and coefficient of friction, as compared to the relatively low metal loss and coefficient of friction observed for Ni. At slightly higher acid concentration (10 to the -3 and 10 to the -2 N), no corrosion products were produced on both Fe and Ni. Wear of Fe and Ni was generally at a minimum. At higher acid concentration (10 to the -1 N and above), loss of Fe and Ni increased as the acid concentration increased. In sulfuric acid the maximum loss of both Fe and Ni was at 7.5 N (30%) concentration, and the metal losses of both Fe and Ni dropped markedly at 15 N (50%) and above. In hydrochloric acid, however, the Fe loss continued to increase with the increase of acid concentration, and the maximum Fe loss occurred in the most concentrated acid (12.1 N, 37%). There were variations in loss with Ni from specimen to specimen examined in hydrochloric acids (10 to the -1 N and above). The coefficient of friction for Ni increased slightly with an increase in acid concentration up to 10 to the -2 N. When corrosion started to dominate in the wear-corrosion process, the coefficient of friction decreased in both sulfuric and hydrochloric acids at 10 to the -1 N and above.