Influence of Cu addition on the corrosion resistance of AISI 304 stainless steel in acid mediums

摘要

The influence of Cu addition on the resistance corrosion of AISI 304 stainless steel in acid mediums (50% solution H_3PO_4 at boiling, 65% solution HNO_3 at boiling and 30% solution H_2SO_4 at 50°C) has been studied. A kinetic study of the corrosion process has been carried out using gravimetric tests. By means of cyclic polarization curves the pitting and repasivation potentials have been obtained. The nature of corrosion products was analysed by SEM and EDS studies before and after accelerated tests to determine the influence of Cu addition on the corrosion behaviour during the exposition to the corrosive environment. Although the chemical resistance of these steels to nitric and phosphoric mediums is high, an increase of the Cu concentration greatly improves the behaviour of AISI 304 stainless steel in sulphuric acid solution. Pitting corrosion resistance decrease with increasing Cu as alloying in 3.5wt% NaCl solution at room temperature. However, the addition of Cu increases the passivation ability of pits.