Our earlier publications have revealed that version of the AP-CITROX technology applied for chemical decontamination of the steam generators (SGs) of the Paks NPP was not adequately developed considering its chemical, analytic and corrosion aspects. To replace the AP-CITROX procedure, novel "soft" chemical decontamination technologies have been elaborated at the Institute of Radiochemistry and Radioecology of the University of Pannonia. Present paper deals with the comparative study of the corrosion and surface chemical effects of the novel chemical decontamination technologies. The chemical composition and morphology of the oxide layer formed on the inner side of the austenitic stainless steel specimens before and after the full decontamination process were studied by scanning electron microscopy (SEM), equipped with an energy dispersive X-ray microanalyzer (EDX). The passivity of the inner surfaces of the stainless steel samples was studied by voltammetry. The full decontamination cycle has been performed under laboratory conditions in a pilot plant circulation system elaborated earlier. In various steps of the chemical procedure the concentration of the main alloying components (Fe, Cr, Ni) dissolved from the surface oxide layer into the decontamination solutions was determined by ICP optical emission spectrometric (ICP-OES) method. Based upon the ICP-OES results the average thickness of the oxide layer removed from the surface into the solutions was calculated. The activity concentrations of the radionuclides (⁶⁰Co, ⁵⁸Co, ¹¹⁰Ag, ⁵⁴Mn) measured in the decontamination solutions allow us to draw conclusions concerning the efficiency of the main steps of the technology and depth distribution of the radionuclides on the treated steel surfaces.