Corrosion of condenser tube materials in distilled water

This paper reports studies related to problems of vapour-side corrosion of copper/nickel alloys in multistage flash desalination plant. The main objective of the work was to obtain basic information and understanding of the corrosion behaviour of copper/nickel alloys in distilled water over a range of relevant environmental conditions. Some attention was also devoted to titanium and an austenitic stainless steel. The experiments were conducted in controlled laboratory conditions with assessment of corrosion behaviour mainly involving electrochemical monitoring. The results demonstrated a clear superiority of the Cu/30Ni alloy over Cu/10Ni material at ambient temperatures and also nonprotective behaviour of both alloys upon initial exposure to distilled water at 80°C. In the time scales of the experiments (up to 15 days), no evidence was found that the presence of carbon dioxide at 80°C made the water significantly more aggressive to the copper/nickel alloys. The superiority of the Cu/30Ni alloy over Cu/10Ni at lower temperatures did not appear to extend to the higher temperatures (80°C) studied. Certainly at short exposure times, titanium and UNS S31603 stainless steel posses considerably superior corrosion resistance than the copper/nickel alloys over the entire range of conditions studied.

Distilled water at 80°C represents a much more corrosive environment than at 20°C but the injection of CO2 does not appear to act as an additionally aggressive agent at 80°C. Cu/30Ni alloy is more corrosion resistant than Cu/10Ni at 20°C but the distinction between the two alloys is reduced in the more aggressive higher temperature distilled water. Titanium and stainless steel provide a marked improvement in corrosion resistance compared to the copper/nickel alloys over the range of distilled water conditions studied.