Corrosion studies on 316L fusion zone and base metal in natural sea water by weight loss method

Abstract

Corrosion studies were carried out on AISI 316L stainless steel weldments.Corrosion rates were measured on base metal (BM) and fusion zone (FZ) under as -received conditions. Regions welded by Tungsten Inert Gas (TIG) process display complex solidified microstructure. The corrosion tests were conducted in Arabian Sea for the durations of 1, 2 and 3 months. Weight - loss method was adopted to find the corrosion rates. Microstructures of two materials being different, offer different resistance to a given corrosive condition. The breakdown of passivity occurs by the aggressive attack of halide ions on the oxide film, the nature of which depends on the anode potential, environment and inhomogeneity on the surface of the metal. Pitting and other surface variations like layer formation due to sea water microbes were studied and characterization was done by Scanning electron microscope (SEM) along with Energy Dispersive Spectrometer (EDS) for finding composition of the two materials after and before exposure. Experiments showed that under as recieved condition corrosion on fusion zone were severe compared to that of parent metal.