Influence of Mo concentration on corrosion resistance to HF acid solution of Ni–Co–Cr–Mo alloys with and without Cu. (October 2015)

• Record Type: Journal Article
• Authors: Hou, Yuhang; Li, Yunping; Wang, Fenglin; Zhang, Chen; Koizumi, Yuichiro; Chiba, Akihiko
• Is Part Of: Corrosion science. Volume 99(2015)
• Page Start: 185
• Page End: 193
• Publication Date: 2015-10
• Subjects: Interfaces (C) -- Alloy (A) -- Acid solutions (A) -- Acid corrosion (C) -- Cobalt (A) -- Nickel (A); Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2015.07.004
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Corrosion resistance of Ni–Co–Cr–Mo alloys to HF acid was examined. Cu was added to the alloy to test corrosion resistance relative to Mo content. Decreasing Mo content in Cu-free alloys increased corrosion at boundaries and grains. Critical Mo concentration of 11.5% was observed to maintain enough corrosion resistance. wt% Cu addition improved corrosion resistance regardless of Mo content. Abstract: The corrosion resistance of Ni–30Co–16Cr–6Fe– x Mo and Ni–30Co–16Cr–6Fe–2Cu– x Mo ( x = 7–15 wt%) alloys was investigated by immersion tests in 5.2 M HF solution at 100 °C. The weight loss of the Ni–30Co–16Cr–6Fe– x Mo alloys relative to Mo concentration after immersion followed a Boltzmann equation. With decreasing Mo concentration, the Ni–30Co–16Cr–6Fe– x Mo alloys first lost the Mo protection of the grain boundaries, then the annealing twin boundaries, and finally the grain matrix. In contrast, decreasing Mo content did not cause a significant increase in Ni–30Co–16Cr–6Fe–2Cu– x Mo alloy weight loss, but led to a slightly preferential dissolution of both grain and annealing twin boundaries.