Selective phase corrosion and cavitation erosion behaviors of various copper alloys in 3.5% NaCl solutions with different pH values
(1. College of Mechanical and Electrical Engineering, Hohai University, Changzhou 213022, China;
2. College of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China)
2. College of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China)
Abstract: The stability of each phase in nickel aluminum bronze (NAB), manganese aluminum bronze (MAB) and manganese brass (MB) was characterized by scanning Kelvin probe force microscopy (SKPFM). Selective phase corrosion (SPC) and cavitation erosion (CE) behaviors of these materials were studied in 3.5% NaCl solution with different pH values. The results show that the κ phase with the lowest stability is dissolved in the acidic solution (pH 2) for each material. In the neutral solution (pH 6.8), the Al-abundant κ phases in NAB are preserved, whereas the Fe-rich κ phases in MAB and MB are dissolved. In the alkaline solution (pH 12), pitting corrosion occurs at the κ phases in MAB and MB and at the κII phase in NAB. In each solution, NAB possesses the highest CE resistance, followed by MAB and MB. In the acidic solution, SPC remarkably intensifies the CE damage and CE-corrosion synergy contributes largely to the CE degradation. In other solutions, slight SPC occurs and each material exhibits a mechanical attack- dominated CE mechanism.
Key words: copper alloys; scanning Kelvin probe force microscopy; selective phase corrosion; cavitation erosion; synergy