Monitoring the Corrosion of Copper-Nickel-Chromium Castings Using Electrochemical Frequency Modulation

Cast nickel aluminum bronze has been used extensively in some components in seawater systems because of its generally good toughness. However, this alloy can be susceptible to selective phase corrosion, which has led to requirements for removal of components on a fixed timetable to test for the presence of this corrosion. In an effort to reduce the costs associated with these inspections, some of these components will be replaced with those made from a cast copper-nickel-chromium alloy. This alloy should be free from this form of corrosion, particularly after the development of a protective film during exposure to clean, flowing seawater. Polluted seawater containing sulfides can interfere with the development of this protective film on other copper-nickel alloys. Electrochemical frequency modulation, along with other electrochemical techniques, will be used to monitor the effects of initial exposure to clean seawater or to polluted harbour water on the corrosion of cast copper-nickel-chromium specimens.