Multi-elemental mapping based on the combination of passive, non-destructive Diffusive Gradients in Thin films (DGT) with LA-ICP-MS enables in situ visualisation and quantification of chemical processes occurring at reactive interfaces. For the last nearly 30 years, DGT has been applied primarily for environmental analysis. Recent studies opened a new perspective for understanding corrosion processes as part of materials science [1].
In this study, a novel application of DGT LA-ICP-MS for the in situ multi-elemental mapping of localised corrosion is presented on the example of aluminium. DGT Polyacrylamide- and polyurethane-based binding gels with homogeneously distributed iminodiacetate (Chelex 100) and TiO2 (Metsorb) binding phases were applied to Al specimens composed of Al and other trace elements (e.g. Fe, Cu, and Zn). The DGT-Al setup was immersed for 24 and 72 hours in a NaCl solution (w = 1.5%, pH = 4.5) at room temperature. The binding gels were evaluated and analysed by LA-ICP-MS. The DGT-Al setup was further optimized in order to minimize crevice corrosion in the DGT – Al interface. Quantification was done by linear calibration using DGT standards with known analyte mass loadings. Imaging was complemented by SEM/EDX microscopy of the metal surface.
The first results obtained on elemental fluxes showed a high flux of Al after 24 and 72 hours, with a similar distribution pattern to the original corroded metal surface. However, the Fe flux after 72 hours showed a more localised release of the corrosion products, which can also be seen with SEM.
The obtained results show that DGT in combination with LA-ICP-MS enables in situ mapping of Al, Fe, Cu, and Zn metal solubilisation, and the DGT flux provides quantitative information about the spatiotemporal reaction dynamics of corrosion processes.