Ellipsometric and electrochemical studies of the surface films on AISI 304SS in acidic KCNS solution

Surface films formed on solution annealed and sensitised AISI 304 SS in 0.5 M H2SO4 solution in the absence and presence of 0.01 M KCNS have been eval uated for their refractive index and thickness using ellipsometry. The resu lts are correlated to the protectiveness of the surface films formed in thi s environment, as determined by electrochemical potentio-kinectic reactivat ion (EPR) tests. It has been observed that surface films (189-363 Angstrom thick) formed on the sensitised AISI 304 SS in the acidic solution without and with KCNS are non-protective, whereas those formed on the solution anne aled SS (123-134 Angstrom) in the same environment are protective in nature .