Electrochemical Monitoring of Selective Phase Corrosion of Nickel Aluminum Bronze in Seawater

Components made from cast nickel aluminum bronze have been used extensively in some seawater systems because of their generally good toughness. However, this alloy can be susceptible to selective phase corrosion. This has led to requirements for removal of components on a fixed timetable to test for the presence of this corrosion. Signficant savings in cost and labor could be achieved if components were only removed when significant corrosion damage had actually occurred. In an effort to find a useful methodfor online corrosion monitoring. several electrochemical techniques were assessed to determine if they could detect the onset of selective phase corrosion in specimens exposed to clean. flowing seawater that Was subject to occasional injections of sulfides liberated from decaying marine organisms. Prior to immersion in the seawater, individual specimens were subjected to different heat treatments intended to either enhance or reduce susceptibility to selective phase corrosion. At the conclusion of the electrochemical tests. specimens were sectioned and inspected for evidence of selective attack.