Corrosivity Study of Sensitized Welded and Unwelded Austenitic Stainless Steel AISI 304 in Oxidizing and Non-Oxidizing Environment

Abstract

An experimental investigation was carried out to determine the corrosive impact of oxidizing and non-oxidizing environments on sensitized welded and unwelded samples of AISI 304. The selected samples were cut into several sizes. To induce sensitization, the samples were heated and soaked at 750oC at different soaking time intervals such as 30 minutes, 60 minutes, 180minutes, 300 minutes and 600 minutes followed by water quenching [1]. The resultant sensitized weldment and unwelded samples were subjected to immersion duration test each in oxidizing (H2SO4) and non-oxidizing (HCL) media for 5, 10, 15, 20, 25, 30, 35, 40, 45, & 50 minutes respectively. From the results obtained, it was concluded that corrosion rate decreases as soaking time/immersion duration increases, at constant soaking temperature in non-oxidizing medium of hydrochloric acid (HCL). However, the corrosion rate decrease of the unwelded samples of AISI 304 in non-oxidizing medium is greater than that of their welded counterpart as immersion duration/soaking time increases. Similarly, the unwelded and welded samples of AISI 304, in oxidizing medium of H2SO4 have one common characteristic with their corrosion rate decreasing as soaking time/immersion duration increases; but, surprisingly, the welded samples are having lower corrosion rate than that of the unwelded counterpart as the immersion duration/soaking time increases between 5-15minutes; but reverses to a higher corrosion rate than their unwelded counterpart as immersion duration increases between 15-50 minutes. The results showed that each sample reacted differently in oxidizing and non-oxidizing media; hence oxidizing and non-oxidizing media impacted the materials’ properties differently. The sensitization differences of the welded and the unwelded counterpart obtained during soaking time, significantly affected their reactions in oxidizing and non-oxidizing media which led to differences in the corrosive impacts, under the same environment.