Electrochemical simulation of vapour side corrosion of Cu–Ni condenser tubes in multistage flash evaporation distillers

Abstract

AbstractThe corrosion of 70–30 Cu–Ni condenser tubes in the vapour of multistage flash evaporation distillers occurs within a thin water film adhering to the metal surface. This, together with the fact that corrosion involves the alternate formation and dissolution of copper oxides, justifies the application of electrochemical techniques in aqueous solutions for the study of vapour side corrosion. Open circuit potential (OCP) transients were used to establish the effects of vacuum and of O2 , CO2 , and mixtures thereof on the corrosion process. The study was carried out in 4%Na2 SO4 solution at ambient temperatures. The state of vacuum in the distiller was simulated by purging the solution with N2 gas. The OCP of the working electrode tended towards more negative values, revealing the instability of the air formed oxide. This changed slowly to a Cu2O film. Introduction of O2 into the cell resulted in the instantaneous shift of potential towards less negative values. Cuprous oxide was oxidised to hydrated ...