Microstructure and electrochemical behavior of dissimilar bonding of DP ۹۸۰ and S ۵۰۰ MC steels in chloride ion containing environments

The resistance spot welding method is one of the common methods in the automotive industry. Therefore, in this paper, two alloys, DP ۹۸۰ and S ۵۰۰ MC were connected by the resistance spot welding method, and the corrosion behavior of this dissimilar joint was investigated and evaluated for use in the automotive industry. The microstructure properties of the base metals and the joints were studied using an optical microscope. Also, in order to evaluate the hardness due to microstructural changes, a microhardness test was performed. Evaluation of corrosion behavior of base metals and the joints wasperformed using a potentiodynamic polarization test in two media of ۰.۱ M NaCl + ۰.۱ M H۲SO۴ and ۰.۱ M NaCl + ۰.۱ M NaOH. The results of the electrochemical studies in the acidic environment containing chloride ions showed low chemical stability of the all tested samples. While the tested samples showed much better behavior in the alkaline environment containing chloride ions due to the formation of the passive layer. Among the tested samples, the S ۵۰۰ MC steel showed the best corrosion behavior and the welded DP ۹۸۰ alloy showed the worst corrosion behavior due to microstructural differences.

Keywords:

Corrosion , Microstructure , Car , Resistance spot welding , Micro Potentiodynamic polarization