Effect of TIG welding on corrosion behavior of 316L stainless steel

Abstract

3 l 6L stainless steel is one of the most consumable materials in pipe, flange, valve and others. ft is an alloy which was produced to encounter the weaknesses of their basic element such as hardness, strength, corrosion resistant and other properties in certain aggressive condition such as seawater and petroleum environment. In this study, 316L stainless steel was used to study the effect of the cooling method of tungsten inert gas (TIG) welding in causing the corrosion in solution. There are two different cooling methods for each type of metals where the samples were cooled in a room temperature or air cooling while another samples facing the rapid cooling process called quenching. 3 l 6L stainless steel had divided into 3 partitions which is heat affected zone (HAZ), weld metal and base metal. The corrosion behavior and microstructure of weld metal, HAZ, base metal and as-weld (coupled weld and base) were compared together. Microstructure was investigated using scanning electronic microscopy (SEM) through image of grain boundaries on metal. Tungsten inert gas was used to weld the samples. The samples were exposed to the highly corrosive environment in salt spray chamber at 37°C which provide very similar environment as the real marine environment. After being in the chamber for several periods, the samples weight loss analysis was done. The samples continued with test of electrochemical impedance spectroscopy using the frequency response analyzer (FRA) and general purposes electrochemical system (GPES) module. Weight loss anaJysis done before and after the samples being put in the salt spray chamber to determine their changes after several periods. Based on the result, it was determined that corrosion rate of quenching samples more than air cooling samples because of HAZ increased anodic element. So, quenching method as post weld heat treatment (PWHT) increased the corrosion rate of as-weld samples. HAZ samples have less corrosion resistance th