Effects of adsorption of O 2 and H 2 O molecules on the corrosion behavior of the NiTi alloy surface: a DFT investigation

• Published in: Physical chemistry chemical physics : PCCP 2024-09, Vol.26 (37), p.24370-24383
• Main Authors: Wang, Xiaoting, Xie, Dong, Hou, MingXi, Guan, Min, Leng, Yongxiang
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/D4CP02631D

The influence of O and H O adsorption significantly affects the electrochemical corrosion of the NiTi alloy, with unresolved corrosion disparities between the NiTi-B and NiTi-B19' phases. Density functional theory (DFT) calculations are utilized in this investigation to explore the adsorption of O atoms at varying coverages on the NiTi-B (110) and NiTi-B19'(010) surfaces. The goal is to elucidate their oxidation behavior differences. Subsequently, the effect of O adsorption on the dissolution trends of these phases is assessed by inducing Ni/Ti vacancies to simulate alloy dissolution thermodynamically. Additionally, interactions between H O molecules and O-pre-adsorbed NiTi alloy surfaces are examined to simulate the atomic evolution of the oxidized surface under exposure to humid air and corrosive solutions. The findings indicate a propensity of the NiTi-B19' phase to react with O, forming an oxide film more readily than the NiTi-B phase. O adsorption facilitates Ni dissolution and retards Ti dissolution on the alloy surface. Higher O coverage promotes easier dissolution of Ni and Ti atoms on the NiTi-B (110) surface compared to the NiTi-B19'(010) surface, underscoring the greater corrosion resistance of the NiTi-B19' phase. Both clean and O-pre-adsorbed NiTi alloy surfaces physically adsorb H O molecules. Notably, an O monolayer substantially mitigates the detrimental effects of H O molecules on the corrosion resistance of alloy surfaces. This research contributes to a deeper comprehension of the corrosion mechanisms in NiTi alloys.