Study On The Corrosion Behavior Of Weld For Automotive Body

With the development of the car,more and more people pay attention to the phenomenon of car corrosion.High-strength steel has been given a lot of attentions because it can meet the strength requirement of body structure when it can also thin and reduce the overall weight of the car.At the same time,in order to improve the corrosion resistance of the body panels effectively,galvanized sheet is most widely used in the manufacture of some mid-level,high-level white car bodies.In the actual using of automobiles,the car body's localized corrosion phenomenon often occurs,corrosion phenomenon is more evident in the body welding joints.In this paper,the high strength dual-phase DP590 steel and galvanized steel commonly used in car body are the experimental materials.Welding joints samples by resistance spot welding and CO₂ gas shielded welding are research objects.The corrosion law of weld and base metal in different concentrations of NaCl solution and different PH of simulated acid rain are studied,and the corrosion rate of the same weld and base metal in the same corrosion media are compared,then differences of corrosion resistance in the same corrosion environment of CO₂ gas shielded welding and spot welding are studied.In the the two corrosive environments,NaCl concentration and PH of acid rain directly affect the corrosion resistance of weld and base material.The corrosion rate of welding and base metal immersed in three different PH of simulated acid rain and in NaCl solution for 720h are obtained by implementing immersion corrosion experiment and weight loss method.The comparison shows that,with the PH and NaCl of the solution reduced,the corrosion rate of same kind of weld or the base material are increased accordingly.Thus,within a certain range,the lower the PH of acid rain solution or the NaCl concentration is,the more serious the degree of corrosion will be.By comparing the same kinds of samples'corrosion rate in the two corrosive environments,it is found that the sensitivity of the sample in NaCl solution is higher than that of acid rain.NaCl solution can affect samples'corrosion more evidently.In the same corrosion media,the corrosion rate of CO₂ gas shielded welding is higher than that of spot welding,and the corrosion rate of base metal is higher than that of spot welding,so corrosion resistance of the base metal is better than the weld.CO₂gas shielded welding may be more prone to corrode than spot welding in the body structure and should be pay attention to prevent from corrosion.