6 - 70/30 copper–nickel seawater piping systems – use of descaling agents and their effects on corrosion properties

Abstract

Publisher Summary This chapter focuses on the 70/30 copper–nickel seawater piping systems and highlights the use of descaling agents and their effects on corrosion properties. Use of copper–nickel alloys in seawater-cooled heat exchangers is common due to the inherent properties of these alloys—namely, a relatively low corrosion rate, antifouling properties, and erosion–corrosion resistance relative to other alloys. The main causes of failure of copper–nickel alloy components in seawater are usually attributed to either erosion–corrosion at extreme velocities or the pitting phenomena. It is well established that these failures are generally due to detrimental seawater conditions, such as the presence of sulphides or poor designs resulting in extreme flow velocities. Periodic cleaning is necessary on seawater cooling systems due to the gradual formation of scaling and macro-fouling during operation. Several chemicals and procedures can be used to remove these deposits and growths, the most common products being hydrochloric, citric or sulfamic acids. Hydrolancing and mechanical cleaning are in use by the fleet, but these have major drawbacks in terms of costs and labor hours. In addition, most of these methods raise some safety and environmental issues. Three commercial descaling solvents, two hydrochloric acid-based and one phosphoric acid-based, have been identified that claim to be safe, environmentally friendly, and inexpensive and exhibit no detrimental effects on the materials.