M. Jula et al, Journal of Advanced Materials and Processing, Vol. 5, No. 1, 2017, 3-12 3 Statistical Approach to the Corrosion Behavior of Dissimilar Welds of A387-Gr91/AISI316 Steels with PCGTAW Process Mohammad Jula 1 , Reza Dehmolaei 2, , Seyed Reza Alavi Zaree 2 1 M Sc. student, Department of Material Science and Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran 2 Department of Material Science and Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran ARTICLE INFO ABSTRACT Article history: Received 5 December 2016 Accepted 19 December 2016 Available online 15 March 2017 In this study, an attempt has been made to minimize the corrosion rate and maximize the pitting potential of dissimilar metal welded joints of A387-Gr91/AISI316 steels. The process parameters of the pulsed current gas tungsten arc welding (PCGTAW) including the peak current (P), background current (B), pulse frequency (F), and on time percentage (O) were chosen as the factors influencing the corrosion behavior. Design of Experiments (DOE) was done using Taguchi’s L9 (34) orthogonal array. The signal to noise (S/N) ratio analysis indicated that corrosion rate was affected by the peak current, frequency, on time percentage, and background current, whereas the pitting potential was mostly influenced by on time percentage, peak current, frequency, and background current, respectively. Optimum conditions of P, B, F, and O factors were found as 135A, 75A, 10Hz, 80% for corrosion rate and 120A, 60A, 6Hz, 60% for the pitting potential, respectively. Furthermore, analysis of variance (ANOVA) demonstrated that the contribution of P, B, F, and O was 28.79%, 13.06%, 28.63%, and 29.51% for corrosion rate and 13.97%, 2.79%, 12.20%, and 71.04% for the pitting potential, respectively. Results of the welded samples at optimum conditions showed good agreement with the predicted values for corrosion rate and the pitting potential. Keywords: Taguchi method Analysis of variance (ANOVA) Pulsed current gas tungsten arc welding (PCGTAW) Dissimilar welding A387-Gr.91 AISI316 1-Introduction Boiler components, such as main steam piping and the header parts of boilers, are usually exposed to high thermal stresses. A387- Gr.91steel is one of the suitable candidates for the mentioned application that explores good creep and fatigue resistance [1]. In other words, due to high corrosion, oxidation and creep resistance of austenitic stainless steels, super- heater and re-heater parts are made of these alloys [1, 2]. The welding of these two dissimilar steels by different welding routes has been the subject of  Corresponding author: E-mail address: Dehmolaei@scu.ac.ir wide research. Usually, the shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) processes are applied to weld these alloys. The major problem encountered with the using of austenitic stainless steels as filler metals is possible carbon migration from ferritic steel to the welding metal and brittleness of the weld especially in the service temperatures more than 315°C. Welding of parts like tubes in the boiler that are in contact with the sulfurous environment by nickel-base fillers such as ERNiCrMo-3 is one solution to overcome the problem [3, 4, 5].