Abstract
Due to their good corrosion resistance in seawater, tubes, rods, and forgings made from copper-nickel alloys (Cu-Ni) are widely used in ship building, offshore platforms, desalination plants, and numerous other applications. Welding is a major technology for joining this material. Since the microstructures of base material, weld seam, and heat affected zone may be quite different, the consequences with respect to corrosion must be considered. In this study the influence of microstructure on corrosion behaviour was investigated using welded test coupons of CuNi10Fe1.6 Mn, as-welded and after heat-treatment, by metallographic examination and electrochemical corrosion tests in synthetic seawater.
Highlights
Copper-nickel alloys (Cu-Ni) have been in extensive use in seawater applications for many years
The higher corrosion resistance of Cu-Ni alloys is attributed to the fact that nickel ions are incorporated in the Cu2O barrier layer formed, which leads to a reduced ionic conductivity in the Cu2O and to a higher corrosion resistance [6]
After the dissolution of these surface-near dendrites, since they are surrounded by the nickel-rich inter-dendritic phase, the corrosion at the weld seam will cease and the further corrosion process will be dominated by a dissolution of the parent metal
Summary
Copper-nickel alloys (Cu-Ni) have been in extensive use in seawater applications for many years. These materials offer a good corrosion resistance and excellent antifouling properties [1]. The addition of nickel to copper improves the resistance against uniform and pitting corrosion and increases the mechanical strength of the alloys [2,3,4,5]. In alkaline solutions containing chloride, nickel contents above 10% deteriorate the pitting corrosion resistance [2]. The corrosion resistance of copper nickel alloys decreases with chloride concentration and temperature [3, 6, 9,10,11]. The addition of some iron to Cu-Ni alloys was found to further improve the corrosion resistance against seawater [12]
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