Scanning Kelvin probe study of steel/oil interfaces for corrosion evaluation

Rust preventive oil (RPO) provides temporary protection to steel during storage and transit. Premature failure occurs as surface defects due to inefficient RPO quality. Conventional corrosion tests like salt spray and cyclic corrosion provide minimum information about corrosion mechanism. We applied separately three RPO, named here as A–C, on bearing steels and their corrosion performance was examined by scanning Kelvin probe (SKP). The corrosion potential of samples lowered after oil application. It seems that oil film delayed oxygen reduction reaction. Later, oiled samples were exposed in salt spray test (SST) and again examined by SKP at different time interval. The SKP result showed that oiled sample A corrosion potential increased during SST exposure. Oil A might develop passivity on steel surface. It is also supported by least red rust formed on oiled sample A in SST. Fourier transform infrared spectroscopy, inductively coupled plasma and chemical analysis of oils were performed to interpret the SKP outcome. Oil A possesses low oxidation peak, low total acid number, and high total base number that signify higher corrosion resistant. Finally, SKP findings are in‐line with the conventional corrosion tests‐salt spray and condensation water tests.