Effect of Pulse Current Micro Plasma Arc Welding Parameters on Pitting Corrosion Rate of AISI 321 Sheets in 3.5 N NaCl Medium

Abstract

Austenitic stainless steel sheets are used for fabrication of components, which require high temperature resistance and corrosion resistance such as metal bellows used in expansion joints in aircraft, aerospace and petroleum industries. When they are exposed to sea water after welding they are subjected to corrosion as there are changes in properties of the base metal after welding. The corrosion rate depends on the chemical composition of the base metal and the nature of welding process adopted. Corrosion resistance of welded joints can be improved by controlling the process parameters of the welding process. In the present work Pulsed Current Micro Plasma Arc Welding (MPAW) is carried out on AISI 321 austenitic stainless steel of 0.3 mm thick. Peak current, Base current, Pulse rate and Pulse width are chosen as the input parameters and pitting corrosion rate of weldment in 3.5N NaCl solution is considered as output response. Pitting corrosion rate is computed using Linear Polarization method from Tafel plots. Response Surface Method (RSM) is adopted by using Box-Behnken Design and total 27 experiments are performed. Empirical relation between input and output response is developed using statistical software and its adequacy is checked using Analysis of Variance (ANOVA) at 95% confidence level. The main effect and interaction effect of input parameters on output response are also studied.