Oil ash corrosion is investigated by studying the oxidation of nickel coated with V2O5. The kinetics of oxidation of pure nickel and coated nickel samples were studied at a fixed temperature under a controlled pure O2pressure. The values of the parabolic rate constant k for a given change in mass are compared for various O2pressures PO2and different deposit thicknesses e. For e = 5 × 10-7m (0.5 μm) at 900 °C the curve of k vs. PO2passes through a maximum for PO2= 20 kPa (200 mbar). The corrosion of V2O5-coated nickel is three times more rapid under this critical pressure than the oxidation of nickel without the deposit. For PO2= 20 kPa, k is proportional to the thickness e. The corrosion could be due to an (Ni, V) oxide located along defects of the oxide NiO (grain boundaries and pores), facilitating the cationic diffusion through the corrosion product at 900 °C. © 1987.
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