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Surface modification with self-assembled alkyl-phosphonic acid layers is a powerful technique for corrosion protection of different metals. In the present study, passivated, native (covered with air-formed oxide) and metallic iron surfaces were used as substrates. The influence of the oxide on the phosphonate layer formation; the corrosion protective effect of the phosphonate layer and the structure of the modified surfaces were investigated. The layer formation process was monitored directly in the phosphonate-containing solution. It was found that the phosphonate layer formation process depends on the conditions applied during iron passivation, and the oxide layer has an important role in the stability of the protective layer, while the bare metallic iron surface is disadvantageous for phosphonate bonding. Conversion electron Mossbauer spectroscopy (CEMS) and X-ray photoelectron spectroscopy (XPS) proved the presence of phosphonate layer on the top of the passive iron surface, with the thickness around monolayer.

Phosphonate layer formation on passive iron surface has been investigated by electrochemical, conversion electron Mossbauer spectroscopy (CEMS) and atomic force microscopy (AFM) techniques. Electrochemical methods revealed that the prepassivation of iron surface results in stabilization of the phosphonate layer exhibiting favorable corrosion resistance. The rate of anodic dissolution is continuously decreasing due to the time-dependent formation of a protective phosphonate layer. The large R ct values of 1–20 MΩ cm 2 indicate rather high blocking effect of metal dissolution by the phosphonate layer. The phosphonate layer formation has been also followed by the decrease of capacitance. CEMS investigations were carried out to evaluate the differences in the composition of the passive layer as a result of the phosphonate treatment. Mossbauer spectroscopy indicated the presence of iron phosphonate. Changes in morphology due to the phosphonate layer formation have been observed.

Mossbauer spectroscopy and electrochemical measurements were used to study the passivation of iron and steels in a sulphite containing solution. The potentiodynamic curves show that passivation occurs at −140 mV potential vs saturated calomel electrode ( sce ). The main phase of the passive layer was found to be γ-FeOOH, while FeSO 4 ·H 2 O on the surface and FeSO 3 ·3H 2 O inside the layer were identified as minor phases in the case of polarization in a solution of pH 3.37. Only γ-FeOOH was observed on the surface of samples polarized at pH 6.6.

X-ray diffractometry, Mossbauer spectroscopy and DTA measurements have been used to study the relaxation and crystallization processes in electrodeposited Fe 31 Ni 45 P 23 amorphous alloys. The changes in the Mossbauer spectra and in the hyperfine field distributions due to aging at 205°C have been associated with changes in the short range ordering in amorphous state. Ni, (NiFe) 3 P and (NiFe) 2 P phases have been identified during the crystallization.