INFLUENCE OF INTERMITTENT FLOW ON CORROSION INHIBITION OF STEEL IN NEUTRAL AQUEOUS SOLUTIONS

摘要

Electrochemical impedance measurements were combined with current-potential curves to investigate the effect of flow conditions on the corrosion behaviour of carbon steel rotating disk electrodes in a model water with and without the presence of 10 ppm of a inhibitor mixture consisting of N-phosphono-methyl-glycine (NPMG) and Zn~(2+) ions in a concentration ratio of 1:1. Results showed that for operation at constant rotation speeds both in the blank and inhibited solutions, the corrosion rate is lower at the higher rotation speed. Due to intermittent flow operation, corrosion rate of the steel electrode increased in model water solutions, and remained almost unchanged in inhibited solutions. Inhibiting layers proved to be more stable to changes in flow condition than corrosion product layers developed in the blank solutions. Results suggest that for the system investigated in this work, the mechanism of the partial anodic reaction is affected by fluid flow conditions.