Copper Alloys in Seawater: Avoidance of Corrosion (CDA Publication 225)

About this Publication

Copper alloys have been widely used in seawater and related brines, such as in thermal desalination plants, for many years, generally with excellent results. They are commonly used for piping, valves, pumps and heat exchanger tubing, but have found many other applications.

Occasionally there are failures due to corrosion, and in many cases these could be avoided by following some simple design recommendations, by selecting an alternative copper alloy, or by using a simple preventative strategy. This document covers the most common types of corrosion and shows simple methods to avoid them. If these are implemented at the design stage, it can save a large expenditure after a corrosion failure.

This guide has been written principally for marine, mechanical and other engineers who have to select materials of construction but do not have a corrosion background.

Links to individual sections in the publication are available by clicking on each section below. The entire book can also be downloaded as a pdf.

Whilst this publication has been prepared with care, we can give no warranty regarding the contents and shall not be liable for any direct, incidental or consequential damage arising out of its use. For complete information on any material the appropriate standard should be consulted.


Summary An introduction to the topics and examples of typical end uses.
Section 1 Alloys
Section 2 Information
Section 3 Velocity 
Section 4 Temperature
Section 5 Pollutants
5.1 Sulphide
5.2 Ammonia
Section 6 Fouling and Chlorination
Section 7 Coupling to Other Alloys
Section 8 Start-up
Section 9 Quality
9.1 90/10 Copper-nickel
9.2 Nickel Aluminium Bronze
9.3 Heat Exchanger Tubing
Section 10 Conclusion 
Section 11 References 
Section 12 Appendix
12.1 Ferrous Sulphate Dosing
12.1.1 Role of Ferrous Sulphate
12.1.2 Dosing Practice
12.2 Appendix References
Table 1 Nominal Composition of Copper Alloys Discussed in the Guide
Table 2 Safe Velocities for Copper-nickel Tube and Pipe
Table 3 Maximum Weld Bead Protrusion for Copper-nickel Piping
Table 4 Recommended Safe Chlorine Dosing for some Copper Alloys
Table 5 Alloy Groupings for Galvanic Corrosion in Seawater at Ambient Temperature
Figure 1 90/10 copper-nickel piping on a marine chemical tanker
Figure 2 90/10 copper-nickel tubing in an oil cooler
Figure 3 Erosion corrosion of 90/10 copper-nickel after the weld on a weld neck flange due to excessive flow velocity
Figure 4 Diagram showing syphonic air release
Figure 5 Severe erosion corrosion of 25.4 mm OD 66/30/2/2 Cu-Ni-Fe-Mn in a dump condenser due to syphonic air release
Figure 6 Pitting attack of 90/10 copper-nickel due to sulphide in the seawater
Figure 7 Ammonia induced attack of 90/10 copper-nickel heat exchanger tube
Figure 8 Erosion corrosion of a scratch on an aluminium brass condenser tube due to excessive chlorination
Figure 9 Effect of chlorine on the corrosion of a 90/10 copper-nickel pipe coupled to one of 6% Mo austenitic stainless steel
Figure 10 Corrosion of nickel aluminium bronze pipe along seam weld due to residual beta-phase