OFThe in situ spectroscopic investigation of electrochemical, and especially corrosion processes in iron requires well-characterized reference substances. It has been found that the application of spectroscopic methods alone is not sufficient for the detection of impurities in certain phases. Thermoanalytical methods have therefore additionally been used to detect impurities and to optimize the preparation methods. Infrared and Raman spectra and thermoanalytical data on aFeOOH, fl-FeOOH, ~,-FeOOH, &FeOOH and on amorphous iron(Ill) hydroxide sol are rqaorted.The in situ investigation of the electrochemical behaviour of iron by means of FTIR (Fourier transform infrared) and Raman spectroscopy requires the spectra of possible reaction products for identification. The iron oxyhydroxides ,t-FeOOH, flFeOOH, ~-FeOOH and 6-FeOOH and an amorphous iron(III) hydroxide sol were prepared and were examined by X-ray techniques, infrared and Raman spectroscopy, and thermoanalytical methods. Experimental Methods of preparation

In situ FTIR spectroscopic investigations of the electrochemical reactions of iron in alkaline electrolytes using the internal reflection (ATR) geometry are presented in this paper. During cyclic voltammetric experiments, Fe(OH)z is found to be the product of the oxidation reaction Fe(0) --~ Fe(II), and of the reduction reaction Fe(III) --* Fe(II), whereas 8-FeOOH is formed at the oxidation reaction Fe(II) --> Fe(III). Differences between the first and the second cycle are explained by the amount of Fe(OH)2 present on the electrode surface.