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 (-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.