Study of the corrosion behavior of electroplated iron-zinc alloys using X-ray photoelectron spectroscopy

The corrosive behavior of iron-zinc alloys that have been electroplated on mild steel in both aerated and deaerated quadruply distilled water has been studied using core and valence band X-ray photoelectron spectroscopy. Three alloys were electroplated for comparative purposes with a 17%, 41%, and 83% iron composition. Three alloys of each type were either left untreated or exposed to either detreated or aerated water. No oxidation above that for the untreated samples was found for the samples immersed in deaerated water. As expected, the 83% iron alloy was oxidized in aerated water. However, the 17% iron alloy showed decreased oxidation in aerated water with respect to the untreated alloy. The 41% iron alloy in deaerated water showed no increased oxidation above that of the untreated sample, but it did show increased oxidation in aerated water. The valence band region proved valuable for diagnostic purposes, and had features that could be understood by comparing the experimental data with spectra calculated from band structure calculations. The 17% iron alloy forms a protective zinc oxide surface, while the 41% iron alloy forms a much less protective iron-zinc spinel (Fe2ZnO4). The iron-rich alloy forms an unprotective FeOOH surface layer.