Study of erosion - corrosion under impingement by a fluid jet

Abstract

Influence of flow on corrosion behavior of stainless steel, brass and aluminum wa,~ studied using electrochemical measurement techniques. Flow effect was identified by comparing erosion~corrosion situations with pure corrosion studies. For this purpose, polarization techniques and open~circuit potential measurements were applied in both quiescent and flow conditions. A closed flow~loopin combination with submerged impinging jet system was used to simulate flow conditions similar to industrial fluid flow at bends and disturbed conditions. The experimental setup showed satisfactory performance within the range of operation. Polarization behavior was observed in artificial seawater, sodium carbonate and ferrous sulfate. Active~passive behavior was observed for stainless steel in all environments (except in ferrous sulfate with ferric chloride). Brass and aluminulIl showed active~passive behavior with sodium carbonate. However, in flow condition passive zone of aluminum was totally absent. The polarization curves were found to shift with increasing flow rates indicating increase in corrosion rate. Open~circuit potential (OCP) transient of the observed metals/alloys indicated the nature and extent of corrosion on the sample by the environment. ClCP was obtained in artificial seawater and sodium carbonate solution. Three distinct type of curves were found for all the metal~environment combinations. Increasing OCP potential indicated noble metal behavior while decrease in OCP indicated corro~ sion of the material in the exposed environment. Directional shift in the OCP iudicated changes in the surface phenomena. Heuce, shape of these cmves provides information about the nature and extent of metal environment interaction. Experimental observations showed the applicability of open circuit measurement for on~line corrosion monitoring.