Influence of nano chromium addition on the corrosion and erosion–corrosion behavior of cupronickel 70/30 alloy in seawater

Abstract Cupronickel alloys have found widespread use in various applications such as heat exchangers, refrigeration systems, equipment, pumps, and pipes. However, the inherent structure of cupronickel alone may not be able to withstand certain aggressive environments effectively. To address this issue, the mechanical properties and corrosion resistance of cupronickel alloys can be enhanced by carefully selecting the appropriate alloying compositions. The addition of nano chromium (20 nm) has been proposed as a means of designing cupronickel alloys with improved performance. In the present study, corrosion and erosion–corrosion behaviors of cupronickel 70/30 alloys produced by the casting method without and with three different additions of nano Cr (1, 1.2, and 1.5 wt%) were investigated. The prepared specimens were subjected to electrochemical tests in 3.5 wt% sodium chloride solutions to evaluate their corrosion behavior. Additionally, an erosion–corrosion test was conducted at an impact angle of 90°, using a slurry solution containing 1 wt% SiO 2 sand in 3.5 wt% NaCl solution as the erodent. The specimens were comprehensively characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques. The surfaces of the alloy specimens exhibited superficial attacks, but no pits were observed. Moreover, the surfaces developed a greenish coloration. The electrochemical tests conducted using saline solution revealed that the corrosivity of the cupronickel alloy with nano chromium addition varied from moderate to low, depending on the selected concentration. Despite undergoing corrosion in the saline environment, the modified cupronickel alloys demonstrated good resistance to this corrosive process. Therefore, they can be considered suitable for use in highly aggressive environments, such as in seawater capture systems. The erosion–corrosion test results indicated that the addition of nano chromium significantly enhanced the resistance of the specimens to erosion–corrosion. At 1.5 wt% Cr, the erosion–corrosion rate was reduced by 99.27%.