THE CORROSION OF A LOW-ALLOY STEEL IN A STEAM-TURBINE ENVIRONMENT - THE EFFECT OF OXYGEN CONCENTRATION AND POTENTIAL SCAN RATE ON INPUT PARAMETERS USED TO COMPUTER MATCH THE EXPERIMENTAL POLARIZATION CURVES

The corrosion behaviour of A-470 low alloy steel in a simulated low pr essure steam turbine environment at ambient temperature has been exami ned as a function of dissolved oxygen (DO2) concentration. A computeri zed routine was used to synthesize, match and deconvolute experimental potentiodynamic polarization curves. The empirical relationships betw een the input parameters required to match the experimental polarizati on curves at different potential scan rate (nu) and DO2 levels has bee n established. The effect of increasing DO2 level and nu parallel one another. The DO2 concentration resulting in spontaneous passivation wa s between 0.05 and 0.10 ppm whilst concentrations between 2.50 and 3.0 0 ppm led to instantaneous pitting.