The influence of corrosion on the wear of cast iron in sulphuric acid solutions

Abstract

A reciprocating pin-on-disc-type wear machine incorporating an electrolytic cell has been designed to allow study of the effects of corrosion on the sliding wear of cast iron in sulphuric acid solutions. Continuous corrosion potential/time data for like-on-like sliding in 20 and 60 vol.% solutions have been monitored and correlated with accompanying wear rates and wear scar surface morphologies. In the 20 vol.% solution, the graphitic corrosion layer developed was not significantly displaced during sliding and the mechanical action had little effect on the already high corrosion rate of the iron. In the 60 vol.% solution, three regions were observed in the corrosion potential/time profiles. The initial protective sulphate film on the metal surfaces was gradually removed during the early stages of sliding, as indicated by a fall in the corrosion potential. Subsequently, reformation of a sulphate film was accompanied by an increase in potential in the noble direction. Eventually, the potential decreased again progressively with time until the end of the test. This was accompanied by an increase in wear rate, significant abrasion of the surface and complete removal of the sulphate film, following detachment of hard, abrasive particles from the metal surface.