Characterisation of salt films on dissolving metal surfaces in artificial corrosion pits via in situ synchrotron X-ray diffraction

The salt films formed on metal surfaces dissolving inside artificial corrosion pits formed in 1 M HCl have been probed with synchrotron X-ray diffraction. NiCl2 · 6H2O is the main phase in the salt film on nickel, whereas salt films on both iron and 316 L stainless steel are predominantly FeCl2 · 4H2O. However, the salt film on iron has a very fine homogeneous crystallite size whereas that on stainless steel is much coarser. The potential-dependence of the film formed on iron has been determined.