XPS depth profile study of porous zirconia films deposited on stainless steel by spray pyrolysis: the problem of substrate corrosion

Zirconia (ZrO2) films of tissue-like structure and narrow pore size distribution have been deposited by spray pyrolysis using aqueous zirconyl chloride octahydrate (ZrOCl2.8H(2)O) precursor solutions. Stainless-steel sheets, protected or unprotected by a ZnO barrier layer, have been used as the substrate material held at 473 K. The ZnO barrier layers have been deposited on the stainless steel held at 523 K by spray pyrolysis using a zinc acetate precursor. Their property of corrosion protection to stainless steel has been proved by electrochemical polarization measurements in 0.5 M NaCl solution. A complementary study of XPS (depth profiling, mapping) and x-ray diffraction has shown that the unprotected steel substrates were corroded during ZrO2 film post-annealing in air at T greater than or equal to 773 K, whereas steel substrates protected with a compact barrier layer of crystalline ZnO before ZrO2 film deposition did not show surface corrosion even after annealing up to 997 K. Copyright (C) 2004 John Wiley Sons, Ltd.