The effect of inhibitors on the corrosion and tribological characteristics of gray iron sliding against Si3N4 under lubricated conditions

In this study, Na2SiO3, Na2MoO4, (NH2)NS and (NaPO3)6 were selected as inhibitors to slow down the corrosion of gray iron in distilled water. Furthermore, the wear tests of Si3N4-gray iron pair lubricated with these inhibited solutions were carried out on a ring-block tester. The worn surfaces of specimens were observed under SEM and optical microscope. The components and structure of tribofilm formed on the worn surfaces of specimens were analyzed by XPS. The results indicate that the Na2SiO3 inhibitor can effectively prevent the gray iron from corrosion when its concentration in distilled water ranges between 0.01 and 0.1 mol/l. In the wear tests of Si3N4-gray iron pair under o.1 mol/l Na2SiO3 solution lubricated condition, the friction coefficient is as low as that of Si3N4-gray iron pair lubricated with distilled water. And the wear amounts of the Si3N4 and iron specimens are smaller than that lubricated with distilled water. The superior tribological characteristics are due to a tribochemical film formed on the wearing surfaces. The film consists of gel type amorphous SiO2 and silicates and makes the paired surfaces smooth.