Corrosion Behavior Of Q235 Steel,Zinc And Galvanized Steel In Wuhan Soil Environment

Soil is a heterogeneous system composed of solid,liquid and gas.Many physical and chemical properties of soil affect the corrosiveness of soil,such as water content,oxygen content,temperature,conductivity,pH value,Cl-content,SO42-content,etc.Soil corrosion is a complex process which is affected by many factors.Different soil environments have different corrosive factors,so it is of great significance to carry out targeted research for a certain place.As an underground pipeline material,Q235 steel is widely used in Wuhan area,but it's corrosion behavior hasn't been researched well.Soaked Q235 steel in simulated solution of Wuhan soil,then use method as anodic polarization curve,VHX optical microscopy,focused ion beam scanning electron microscopy(FIB-SEM),and energy dispersive X-Ray spectroscopy(EDS),weight lose to investigated the corrosion behavior.Soil of Wuhan district were alkalescence,high rate of water contain,and low rate of ionic concentration.The results show that the corrosion-proof performance of Q235 steel in solution is under influence by the ionic concentration of HCO3-,CO32-,SO42-,Cl-,which of wildly contained in Wuhan soil.Q235 steel will deactivation by the increase of HCO3-?CO32-in solution,the critical concentration of HCO3-?CO32-to form passive film are 0.004mol/L and 0.005mol/L.After 40 days the surface of Q235 steal soaked in original solution covered with pockmark,and pitting for those raised concentration of HCO3-?CO32-,the Q235 steel in high concentrated SO42-,Cl-solution are equal corroded.The corrosion rate of Q235 steel decrease with time and stabilized at lower rate.The corrosion behavior of Q235 steel in Wuhan area of Hubei Province was studied by using the laboratory accelerated corrosion method to control the temperature and humidity.The experimental results show that Q235 steel has changed from non-uniform corrosion to comprehensive corrosion,pitting and peeling appear on the surface,and the size of pitting and peeling thickness increase with time.The corrosion rate decreases with time and tends to be stable.With the development of corrosion,the self-corrosion potential of Q235 steel increases and the self-corrosion current density decreases.