Research On The Corrosion And Aging Behavior Of Typical High-speed Railway Bodywork Materials In The Main Atmosphere In China

As the science and technology developing, the high-speed rail has becoming one of the main transport, its run-time environment contains the seven climate types, the five domestic water system, more than forty types of soil, desert, plateau, acid rain and so on. Its owe unique and uniqueness. Therefore, under the synergistic effect between the macro environment and the micro environment will cause a decline in the performance of the car body, different degree aging, corrosion damage, and even affecting the service life of the train.This article selects two kinds of materials in the car body of high-speed rail as the research objects. They are metal weld materials(weld of stainless steel, aluminum alloy welding parts) and rubber polymer materials(dumbbell, flake). In China, the main typical climate as following: temperate city atmospheric(Peking), temperate maritime atmospheric(Qingdao), sub-hot and humid city atmospheric(Guangzhou), hot and humid ocean atmospheric(Wanning) and acid rain and atmospheric pollution(Jiangjin). In this research, it will do some outdoor exposure tests and evaluates samples once a week. By analysis these samples, it will find out the main typical climate' s influence on the aging of rubber polymer materials. In order to find out the two important and key point, the influence of the corrosion and aging to the materials under a artificial environment and the evolvement mechanism of corrosion and aging. All of these have a practical and theoretical significance to form a system of high iron materials atmospheric corrosion and aging rules.The main results as follow:Firstly, after exposed one year at outdoor, the surface of the metal weld samples only appear lightly corrosion, the pitting corrosion is the main way on the samples and its distribution density appears unevenly, especially the corrosion in the tee joint lap weld and the weld area is more than the parent metal. Then when distinguish the five selected sites' corrosion, we found, compared with other areas, the degree of corrosion of the stainless steel and aluminum alloy weld samples, the most erosive area is the coastal parts. The standout point is that the same corrosion rate of aluminum alloy weld samples is also show in Jiangjin sites. On the basis of the corroding features of the two kinds of metal atmosphere, we can make a conclusion that what cause the corrosion of the aluminum alloy weld samples are chloride ion, natural dust suppression and sulfur dioxide. But to the stainless steel weld samples, the main pollutants is chloride ion and natural dust suppression, and when they are in hot and humid environment, the hot and humid synergy can accelerate the corrosion rate significantly.Secondly, after exposed one year at outdoor, the surface of these sample stations which have most depth cracks is Peking, and the surface of these samples which have cracks are relatively dense in the coastal sites. At the same time, in the mechanical performance testing and the molecular structure testing, we draw a conclusion by analyzing these samples which we set testing point on these sites. It is that the surface of these rubber materials start molecular chain degradation in the aging process, and generate oxygen-containing groups which lead a further aging reaction.Thirdly, It can put forward another predict that the corrosion of the two metal weld is consistent with the samples at outdoor in the indoor accelerated corrosion test. Their only difference is that their corrosion rate is higher than the outdoor testing samples and the complete rust layer has formed basically on the surface of their joint. According to the characteristics of the corrosion of the two kinds of materials and the uneven and fragment distribution of the samples on the surface of the potential, we make a micro electrochemistry test on the different area of different period samples after they passed the first test. It shows that the first cycle corrosion of the stainless steel weld is preferred in the heat affected zone. And it would last on the last cycle with the corroding cycle continuing. Besides, the most serious part is the bottom of the parent materials. In accordance with the heat affected zone is the back-plane heat affected zone, steel plate, the base area. And at the different cycle of the aluminum alloy welding parts in different areas, their stiffened plates order are the base area, stiffened plate heat affected zone, the bottom base area and the back-plane heat affected zone. It shows that the most serious corrosion part is the base area and the result is consistent with the pitting corrosion from the perspective of the macroscopic law.Lastly, as the time doing, the surface of the sheet and dumbbell rubber samples aging affect continue and extend to the substrate surface gradually in the indoor accelerated aging test. To test different period of aging specimen in the red-ray molecular structure testing, we figure out that cause the reaction is affected by the ultraviolet irradiation, heat and oxygen in the external environment. The molecular chain appear cross-linking reaction, which lead the external appearance of roughness and grainy are reduced gradually and appear some cracks, and when it show through mechanical property their density increased with the cross-linking reaction, the elongation at break continues to decline, the hardness rise, and the tensile strength add up with the density of cross-linking reaction become frequency at the first period, when it add up to the maximum, it will fall fast and then keep a stable state.