Corrosive wear of cast iron in lubricating oil in presence of sulphuric acid added by drip feed method

Abstract

AbstractAn investigation has been carried out into the corrosive wear of contacting grey cast iron specimens during reciprocating sliding in lubricating oils into which 10 vol.-% sulphuric acid in water was added by a drip feed method. For a base oil, containing no additives, the acid caused partial breakdown of the hydrodynamic oil film between the contacting surfaces, leading to metal/metal contact and some corrosion of the metal by the entrained acid. The ensuing wear damage occurred mainly by the mechanical interactions between the two surfaces, but was enhanced by the chemical degradation processes. Similar tests using a formulated marine diesel engine cylinder oil did not result in significant wear of the cast iron components. The acid was rapidly neutralised by the alkaline additives in the oil and breakdown of the hydrodynamic oil film was not observed. If the formulated oil was preneutralised before the test, the wear rate was increased, but not to the same level as in the base oil. This can be a...