Evaluation of Descaling Chemicals for Use with Titanium, Alloy 625, and Nickel Copper Alloy Heat Exchanger and Piping System Components

摘要

Scaling and macro-fouling experienced by seawater cooling system components aboard U.S. Navy ships results in extensive downtime and manpower expenditures. Previous research conducted by the Naval Research Laboratory in Key West, FL (NRLKW) determined that cleaning of coppernickel with descaling solution does in fact remove the passive/oxide film, which naturally forms in flowing natural seawater on these alloys. However, this does not result in significantly higher corrosion rates and the passive/oxide film’s regrowth is not obstructed. The current research was to determine the effects of both hydrochloric acid and phosphoric acidbased solvents on titanium alloys in the freely corroding, crevice, and galvanically coupled conditions. As well as nickel alloys in the freely corroding and galvanically coupled condition. Additionally, the susceptibility of the titanium and nickel alloys to the formation of hydrides and resultant effects on mechanical properties as result of exposure to the descaling agents were studied at ambient and elevated temperatures.