The corrosion behaviour of AISI 304L and 316L stainless steels prepared by powder metallurgy in the presence of organic acids

The corrosion rates of AISI 304L and 316L stainless steels prepared by powder metallurgy (P/M) have been studied by continuous current electrochemical methods, in organic acid solutions (acetic, formic, lactic and oxalic) at different concentrations. For comparison purposes a simultaneous study was carried out on cast AISI 304L and AISI 316L steels of similar composition. For this investigation polarization resistance was the technique chosen and values for the Tafel slopes and the Stern-Geary constant B were obtained. The sintered AISI 304L, and AISI 316L steels had the highest corrosion rates. Subsequently, a kinetic study of the corrosion process has been carried out. A crevice corrosion mechanism for the materials tested in organic acid has been suggested in accordance with the results obtained for the P/M materials. The crevice attack is localized in the pore areas, close to the powder particle contact zone. (C) 1997 Elsevier Science Ltd.