Applicazione del metodo elettrochimico della riattivazione potenziodinamica per la determinazione della sensibilizzazione di leghe inossidabili. Nota II: Acciai inossidabili ferritici a basso contenuto di interstiziali tipo 18 Cr-2Mo E 22Cr-3Ni-3Mo

The electrochemical potentiokinetic reactivation (EPR) method was applied in order to determine the sensitization of Extra Low Interstitial (ELI) ferritic stainless steels (Type 18Cr-2Mo and 22Cr-3Ni-3Mo) produced according to laboratory scale. These steels were tested after an appropriate series of heat treatments which allowed a solubilized reference state to be obtained, as well as grain boundary precipitation of chromium carbonitrides with (or without) the formation of chromium-depleted areas. The conventional tests with oxalic acid (ASTM A 262) and in copper sulfate-50 percent sulfuric acid were used as comparison tests. The possibility of obtaining alloys free of chromium carbonitride precipitates allows the oxalic acid test to be extended to ELI ferritic stainless steels. A comparison of the results of these two conventional tests with those of the EPR test clearly reveals the possibility of applying the latter to the relatively new types of stainless alloys mentioned above. The EPR test clearly reveals the possibility of applying the latter to the relatively new types of stainless alloys mentioned above. The EPR method must still be extended to other alloys of the same class, in order to better quantify the reproducibility and the sensitization threshold by means of eventual modifications in the test conditions.