The corrosion resistance of three different TiN coatings on iron (single TiN layer, Ti/TiN bilayer and Ti/TiN/Ti/TiN multilayer) subjected to a salt (ammonium sulphate and sodium chloride) fog spray (Prohesion) test has been investigated by means of x-ray photoelectron spectroscopy (XPS). The relative intensities of the Fe 2p and O 1s signals in the XPS spectra of the corroded samples increase with their extent of degradation. The results show that the corrosion resistance of these coatings decrease in the order bilayer>multilayer>single layer. Copyright © 1999 John Wiley & Sons Ltd.