Influence of passive film composition and sea water pressure on resistance to localised corrosion of some stainless steels in sea water

A series of experiments in sea water at different hydrostatic pressures (from 1 to 300 bar) was carried out on some stainless steels containing different amounts of Cr, Ni, and Mo to investigate whether these elements and the hydrostatic pressure could affect the composition of the corrosion layer formed in sea water and the resistance of the steel to localised corrosion. Electrochemical tests and X-ray photoelectron spectroscopy were used. The resistance to both localised and general corrosion was affected by the composition of the passive films. The resistance to localised corrosion of stainless steels at atmospheric pressure was improved by Mo, but lowered at high pressure. However, the presence of Ni improved the corrosion resistance of stainless steels at high pressure.