Regulating the passive film of NiCoCrMo alloy in hydrofluoric acid solution by small addition of Cu

• Published in: Corrosion science Vol. 98; pp. 119 - 127
• Main Authors: Li, Yunping, Xu, Xiandong, Hou, Yuhang, Zhang, Chen, Wang, Fenglin, Omura, Kazuyo, Koizumi, Yuichiro, Chiba, Akihiko
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2015
• Subjects: A. Acid solutions; A. Alloys; A. Cobalt; A. Nickel; C. Acid corrosion; C. Interfaces; A. Nickel; C. Interfaces; A. Cobalt; C. Acid corrosion; A. Alloys; A. Acid solutions
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2015.05.024

•Effect of 2wt.% Cu addition in Ni–30Co–16Cr–15Mo–6Fe was investigated.•Mo-oxide-dominated passive film was replaced with a Cu-dominated film.•Cu addition yielded tremendous improvement in corrosion resistance in HF solutions. The effect of 2wt.% Cu addition on the corrosion resistance of Ni–30Co–16Cr–15Mo–6Fe alloy in hydrofluoric acid was investigated by immersion testing at 100°C. Microstructural observations of the passive film of samples after immersion testing via various methods revealed that the small addition of Cu yielded a tremendous improvement in corrosion resistance, even after cold forging. In addition, the passivation of Ni–30Co–16Cr–15Mo–6Fe alloy by a Mo-oxide-dominated passive film was completely changed to passivation by a Cu-dominated one in Ni–30Co–16Cr–15Mo–6Fe–2Cu alloy during immersion in hydrofluoric acid solution because the segregation behaviour of Cu was much stronger compared to that of Mo.