Crevice Corrosion Performance of Candidate Naval Ship Seawater Valve Materials in Quiescent and Flowing Natural Seawater

A wide range of alloys is being evaluated for use in a new generation of seawater valves for the U.S. Navy. This new generation of valves is being developed to reduce valve life cycle costs and to ensure materials compatibility with advanced seawater piping materials such as commercially pure titanium. Part of the evaluation includes assessing the corrosion performance of candidate valve materials. Crevice corrosion performance is of particular interest since valves are connected to shipboard piping systems with flanges and since valves contain numerous internal crevices. Crevice corrosion tests were performed in constant temperature, natural seawater under both quiescent and flowing conditions. Bronze, copper-nickel, and nickel-copper alloys, which are currently used in Navy valves, were used as standards by which the performance of stainless steel, nickel-base, titanium, and cobalt alloys could be measured. No crevice corrosion was observed on any of the titanium or cobalt alloys tested while the stainless steel and nickel-base alloys ranged from fully resistant to highly susceptible. Wrought alloys were typically more resistant to crevice corrosion than their cast equivalents.