In situ spatiotemporal solute imaging of metal corrosion on the example of magnesium

Stefan Wagner, Christina Hummel, Jakob Santner, Markus Puschenreiter, Johanna Irrgeher, Walter W. Wenzel, Sergey M. Borisov, Thomas Prohaska

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Visualization and quantification of corrosion processes is essential in materials research. Here we present a new approach for 2D spatiotemporal imaging of metal corrosion dynamics in situ. The approach combines time-integrated Mg 2+ flux imaging by diffusive gradients in thin films laser ablation inductively coupled plasma mass spectrometry (DGT LA-ICP-MS) and near real-time pH imaging by planar optodes. The parallel assessment of Mg 2+ flux and pH distributions on a fine-structured, bare Mg alloy (b-WE43) showed intense Mg dissolution with Mg 2+ flux maxima up to 11.9 ng cm −2 s −1 and pH increase >9 during initial corrosion (≤15 min) in aqueous NaNO 3 solution (c = 0.01 mol L −1). The techniques visualized the lower initial corrosion rate in buffered synthetic body fluid (Hank's balanced salt solution; pH 7.6) compared to unbuffered NaNO 3 (pH 6.0), but precise localization of Mg corrosion remains challenging under these conditions. To further demonstrate the capability of DGT LA-ICP-MS for spatiotemporal metal flux imaging at the microscale, a coated Mg alloy (c-WE43) with lower reactivity was deployed for ≤120 min. The high spatial resolution (∼10 μm × 80 μm) and low limits of detection (≤0.04 ng cm −2 s −1, t = 60 min) enabled accurate in situ localization and quantification (U rel = 20%, k = 2) of distinct Mg 2+ flux increase, showing micro-confined release of Mg 2+ from surface coating defects on c-WE43 samples. The presented approach can be extended to other metal species and applied to other materials to better understand corrosion processes and improve material design in technological engineering.

Original languageEnglish
Article number339910
JournalAnalytica chimica acta
Issue number15 June
Publication statusPublished - 6 May 2022

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