Comparative study of electrochemical Corrosion of Novel Designs of 90/10 and 70/30 Copper-Nickel Alloys in Brine Solutions

Copper-nickel alloy is a material of choice for condensers and heat exchangers, where seawater is used as a coolant and in desalination plants. In this work, we survey the comparative corroding behavior of novel designs of 90/10 and 70/30 Copper-Nickel alloys under higher salinity (3.5 wt%, 10 wt% and 15 wt% NaCl). The electrochemical corrosion of Cu-Ni alloys in brine solutions was studied using potentiodynamic polarization, chronoamperometric and electrochemical impedance spectroscopy measurements along with scanning electron microscope (SEM) and energy dispersive X-Ray analyzer (EDX) investigations. Polarization data showed that Cu-10 Ni alloy is more corrosive than Cu-30 Ni alloy in 3.5 wt% NaCl solutions. Chronoamperometric curves confirmed the results obtained by polarization measurements that the uniform and pitting corrosion of Cu-Ni alloy were reduced in the Cu-30 Ni alloy in 3.5wt% NaCl solutions. Impedance spectra revealed that the surface and polarization resistances recorded higher values in Cu-30Ni alloy. SEM/EDX investigations indicated that the corrosion of Cu-Ni alloys proceeded by the selective electro-dissolution of nickel, which allowed copper enrichment on the surface of the alloy. The heat exchanger served to heat desalinated water, the water had a high chloride level. Corrosion examination indicated susceptibility towards pitting corrosion, especially at high temperature.