The hydrothermal chromate treatment of carbon steel. The electrochemical and surface analytical characterisation of protecting oxide layers

In connection with the hydrothermal application of chromate to carbon steel for purposes of nuclear technology, the protecting oxide layers formed under these conditions were characterised by means of electrochemical and surface analytical methods. Potentiodynamic anodic polarisation causes oxidation of incorporated chromium (III) ions with an efficiency varying between 20 and 100%. By means of scanning electron microscopy, electron probe microanalysis, Rutherford backscattering, dynamic secondary ion mass spectroscopy and X-ray photo-electron spectroscopy specific structural features of the layers were shown to be responsible for the different oxidisability of Cr(III). Moreover, identification of the species formed was attempted using Raman microspectrometry, X-ray diffraction and X-ray photo-electron spectroscopy. (Author)