Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, H3A 0B8 Quebec, Canada.
Automotive and Surface Transportation Research Centre, Division of Transportation and Manufacturing, National Research Council Canada, 75 de Mortagne Blvd, Boucherville, J4B 6Y4 Quebec, Canada.
Anal Chem. 2020 Sep 15;92(18):12415-12422. doi: 10.1021/acs.analchem.0c02177. Epub 2020 Aug 25.
This work reports the development of an oil-immersed scanning micropipette contact method, a variant of the scanning micropipette contact method, where a thin layer of oil wets the investigated substrate. The oil-immersed scanning micropipette contact method significantly increases the droplet stability, allowing for prolonged mapping and the use of highly evaporative saline solutions regardless of ambient humidity levels. This systematic mapping technique was used to conduct a detailed investigation of localized corrosion taking place at the surface of an AA7075-T73 aluminum alloy in a 3.5 wt % NaCl electrolyte solution, which is typically challenging in the conventional scanning micropipette contact method. Maps of corrosion potentials and corrosion currents extracted from potentiodynamic polarization curves showed good correlations with the chemical composition of surface features and known galvanic interactions at the microscale level. This demonstrates the viability of the oil-immersed scanning micropipette contact method and opens up the avenue to mechanistic corrosion investigations at the microscale level using aqueous solutions that are prone to evaporation under noncontrolled humidity levels.
本工作报道了一种油浸扫描微管接触法的开发，这是扫描微管接触法的一种变体，其中一层薄油润湿被研究的基底。油浸扫描微管接触法显著提高了液滴的稳定性，允许进行长时间的映射，并使用高挥发性盐溶液，而不受环境湿度水平的影响。这种系统的映射技术被用于对 AA7075-T73 铝合金表面在 3.5wt%NaCl 电解质溶液中发生的局部腐蚀进行详细研究，这在传统的扫描微管接触法中通常是具有挑战性的。从动电位极化曲线中提取的腐蚀电位和腐蚀电流图与表面特征的化学成分以及微尺度水平上已知的电偶相互作用具有很好的相关性。这证明了油浸扫描微管接触法的可行性，并为在非控制湿度水平下容易蒸发的水溶液中在微尺度水平上进行机械腐蚀研究开辟了道路。
