Influence of temperature, chloride content and micro structure on corrosion behavior of 2209 duplex stainless steel welded joint

摘要

The 2209 duplex stainless steel (DSS) is wide used in welded joints in marine environment, because of its excellent combination of mechanical and electrochemical properties. The goal of the present paper is to study the corrosion behavior of a 2209 DSS welded joint in a simulated marine media, and correlate to materials factors such as microstructure and passive film semiconductor properties. Electrochemical characterization was set up in aerated NaCl solutions. First, Tafel curves were conducted in NaCl 3.5%. Then, in order to evaluate the contribution of environmental factors on the corrosion potential, a sequence of polarization tests were selected according to robust design of a three level-three factors Taguchi L9 orthogonal array. The factors considered are the temperature of the medium (20°C to 60°C), the chloride concentration (0.001M to 0.1M), and microstructure. Analysis of Signal-to-Noise ratio and ANOVA were achieved on all measured data and the optimal conditions providing a high corrosion resistance was estimated. Mott-Schottky analysis and EIS measurements were performed and were in a good agreement with corrosion data and SEM/EDS results. Measured impedance data was simulated by the accurate equivalent circuit and the passive film thickness was also evaluated. The calculated donors and acceptor densities confirmed quantitatively that increasing temperature and chloride content affects the doping levels in the 2209 passive film and enhanced its breakdown.