Study of the corrosion layer on iron obtained in solutions of water-polyethylene glycol (PEG 400)-sodium phosphate

The iron behaviour in phosphate/water/polyethylene glycol (PEG) was studied in-situ and ex-situ by spectrometry Raman, ESCA spectroscopy, X-ray diffraction, Auger spectroscopy were used as surface analysis methods. It changes with phosphate concentration. At low phosphate concentration (5 × 10−4 M-10−3 M-5 × 10−3 M), iron is corroded. The thin corrosion layer is a mixture of iron oxides (γ-Fe2O3, Fe3O4) and iron phosphate(Fe3(PO4)2, 8H2O). At high phosphate concentration (10−2 M-5 × 10−2 M), the iron is protected. The protection could be due to an heterogenous layer containing PEG 400 and phosphates.