CEMS study of corrosion products formed by NaCl aqueous solution

Conversion electron Mossbauer spectroscopy was used to study corrosion products by NaCl aqueous solution. A drop of the solution is put on an iron foil and the foil is left at RT. During the evaporation of the solution, corrosion products are formed. Conversion electron Mossbauer spectra were taken at temperatures between 15 K and room temperature (RT). In the Mossbauer spectra a ferric doublet is observed at RT, but sextets are found at 15 K. These results show that the corrosion product mainly consists of gamma - FeOOH and a small amount of beta - FeOOH is noticed. As NaCl concentration increases, the corrosion layer becomes thick and beta - FeOOH / gamma - FeOOH ratio increases slightly. Consequently, it has been concluded that the produced amount of beta - FeOOH increases more rapidly than that of gamma - FeOOH with increasing NaCl concentration.