Study On The Atmospheric Corrosion Grade Evaluation And Corrosion Behavior Of Transmission Tower In Southern Power Grid Region-Hainan Province And Yunnan Province

The transmission tower that serves in natural environment suffered severe corrosion damage due to the atmospheric corrosion and thereby its mechanical performance dropped substantially,which seriously affect the safe operation of power transmission.The lack of the study about corrosion behaviour and the distribution of atmosphere corrosion level of transmission tower of the Southern Power Grid in different atmosphere environment is often observed at present.In this paper,the atmospheric corrosion behaviour and corrosion grade evaluation of transmission tower materials including Q235,Q345 and galvanized steel exposed to different atmospheric environments were investigated on this background.This paper discussed the atmospheric corrosion behaviour of transmission tower material in typical environments from two aspects.On the one hand,the typical environment in Hainan and Yunnan province was selected according to the characteristics of different corrosion environments.Then,the outdoor exposure test was carried out in the marine,industrial,urban and tropical rain forest environment.On the other hand,the indoor simulation experiment was carried out in simulated industrial environment.Then,different concentrations of NaHSO3 solution(0.001,0.005,0.01,0.02 and 0.03 mol/L)were chosen to simulate industrial environment of the different concentrations of SO2 in the atmosphere.Some main conclusions can be made from the full text as following.Firstly,the corrosion weight loss results show that the distributions of the atmospheric corrosion level in the natural environment are obviously different.The corrosion grades of steel in the marine and industrial environment are higher than those in the urban and the tropical rainforest environment.Meanwhile,the corrosion grade of steel in urban atmospheric environment was significantly greater than that in tropical rainforest climate.The corrosion rates in the environment of Dongfang,Wanning and around the power plant are more serious,the corrosion levels of the most areas above are C3 level and the most serious case has reached C4 level.The corrosion rate in Kunming and Xishuangbannan is relatively lighter,the corrosion levels of which are C2 level.The corrosion weight loss of steels in the simulated industrial atmosphere presents the periodic variation with the increase of the concentration of the NaHSO3 solution.Secondly,it is found that the corrosion products on Q235 and Q345 mainly consist of γ-FeOOH and α-FeOOH,and the corrosion products on the galvanized steel mainly consists of ZnO,Zn4CO3(OH)6 and Zn5(CO3)2(OH)6 in Hainan province.The corrosion products on Q235 and Q345 are some different with the exposure time.The corrosion products mainly consist of γ-FeOOH after three-month exposure,however,γ-FeOOH and α-Fe OOH after six-month exposure.As for the galvanized steel,the corrosion products are Zn4CO3(OH)6 and Zn5(CO3)2(OH)6 in Yunnan province.The corrosion products of steels have periodic variation with the increase of the concentration of NaHSO3 solution in the simulated industrial atmosphere.When the concentration of NaHSO3 is less than 0.005 mol/L,the corrosion products on Q235 and Q345 mainly consist of γ-FeOOH.When the concentration is higher than 0.02 mol/L,there are more α-FeOOH and FeSO4.The corrosion products on galvanized steel mainly consist of ZnO,Zn4CO3(OH)6,Zn5(CO3)2(OH)6 and Zn4SO4(OH)6 under different spray concentration.Finally,the results of the observation of the rust layer morphology on steels show that the morphologies of the rust layers formed in the different environments present significantly different.The rust layers that formed in the marine environment are loose and porous,and furthermore many cracks are observed,which leads to a worse protection effect of the corrosion products to the substrate and thereby a worse atmosphere corrosion resistance for Q235 and Q345.The rust layers formed in Xishuangbanna and Kunming are relatively dense,and no cracks are observed.The rust layers on Q235 formed in industrial pollution environment combine poorly with the matrix.The plating layer on the galvanized steel is in perfect condition,which indicates that the substrate steel is not suffered from the atmosphere corrosion.It is found that the surface micro-morphologies of corrosion products on Q235 and Q345 steel mainly consisted of the typical plate of lepidocrocite and typical globular structures of goethite.The morphology characteristics of the hole and crack can be observed after the exposure in both the natural and simulated atmospheric environment.The corrosion grade of the galvanized steel is lighter and some plate-like corrosion products are present.