Kelvin Microprobe Analytics on Iron-Enriched Corroded Magnesium Surface

This work contributes to the better understanding of Kelvin microprobe response to iron re-deposition related surface morphology changes resulting from Mg corrosion caused by iron-rich impurities. Scanning Kelvin probe force microscopy (SKPFM) was performed on polished Mg samples at well-defined surface conditions occurring from corrosive exposure to 0.05 M NaCl electrolyte or dissolved FeCl₂. Volta potential difference was measured and mapped across iron-rich areas, unaffected areas of α-Mg, and on FeCl₂ exposed areas. Afterward, the obtained potential values were evaluated via the derived mathematical expression, based on model assumptions. Subsequently, they were compared and then correlated to the corrosion process. The article demonstrates what kind of information can be obtained by SKPFM and what conclusion can be drawn toward the detailed explanation of recently reported iron re-deposition mechanism on corroding Mg surface. Finally, suggestions toward the improved application of SKPFM for Mg corrosion are made.