CORROSION BEHAVIOR OF AISI 304L AND 316L STAINLESS-STEELS PREPARED BYPOWDER-METALLURGY IN THE PRESENCE OF SULFURIC AND PHOSPHORIC-ACID

The corrosion rates of AISI 304L and 316L stainless steels prepared by powder metallurgy (P/M) have been studied by continuous electrochemic al methods, in different concentrations of inorganic acid solutions (s ulphuric and phosphoric) at room temperature (T = 298 K). For comparis on purposes, a simultaneous study was carried out on similar compositi on cast AISI 304L and AISI 316L stainless steels specially prepared fo r this study. For the latter part of this investigation, polarisation resistance and an intersection method were applied to obtain values fo r the Tafel slopes and the Stern-Geary constant B. The sintered AISI 3 04L and 316L stainless steels had the highest corrosion rates, these b eing much higher in sulphuric acid. Subsequently, a kinetic study of t he corrosion process has been carried out. The most pronounced attack was observed in those steels prepared by powder metallurgy due to a ge neralised mechanism of crevice corrosion taking place in the pores. On the other hand, as is already well known, the cast stainless steels g enerally showed a strong resistance to corrosion in the media tested. (C) 1998 Elsevier Science Ltd. All rights reserved.