Experimental Study On Sandy Soil Properties Of Electrochemical Impedance Spectroscopy And Its Corrosive Behavior Of Q235 Steel

Many factors influence the corrosion of sand system,existing evaluation methods of corrosive soil still have some limitations,the water content and the effect of particle size on soil corrosion and corrosion mechanism deserve a further study.Based on the summarization about soil corrosion and electrochemical impedance spectroscopy(EIS),physical mechanical and electrochemical parameters of sand were investigated;at the same time corrosive behavior and mechanism of Q235 steel with different water content and particle size in sand were studied by the electrochemical workstation and scanning electron microscope(SEM).The main conclusions are as follows:(1)The compression performance of sand test shows that particle size determines the sand pore structure and pore size,larger particle size,larger aperture,porosity is smaller than the relative;under the same vertical load,the void ratio decreases with the increase of particle size;the compressive modulus of sand with larger particle size is smaller.(2)Based on the electrochemical impedance spectroscopy(EIS)of the sand system,the physical meaning of equivalent circuit parameters of sand are analyzed,and discuss the relation between the parameters and the particle size and water content.With the increase of particle size,solid liquid interface capacitance increases,charge transfer resistance and diffusion coefficient of Warburg decreased;with the increase of the water content,solid-liquid interface capacitance increases,pore solution resistance and diffusion coefficient of Warburg decreased.(3)The macro and micro morphology of Q235 steel showed that with the increase of water content,the corrosion products on the sample surface increase,the corrosion area and corrosion degree increase;the corrosion degree is relatively low in the sand system with the water content is 9%,which belongs to local corrosion;with the water content are 12% and 15%,a relatively large and large area of corrosion pits,which belongs to uniform corrosion.(4)It can be concluded that for the 2# system of sand,the lower water content in the soil,the electrode corrosion potential decreases,with the water content increasing,will promote mass transport,accelerate the diffusion of substances and the increase the corrosion rate.When the water content was 15%,different particle size sand system polarization curves remain basically the same characteristics of anodic and cathodic plan curves which are smooth and continuous without obvious passivation area and the cathode Tafel slope is larger than the anode Tafel slope;with the increasing of particle size,thepolarization curve overall upward shift.(5)Electrochemical impedance spectrum(EIS)test of Q235 steel showed that when the corrosion time is 28 days,the Warburg impedance appears in the Nyquist diagram of the Q235 in every sand system,in which the slope of the Warburg impedance of the 2# sand system is nearly 45 degrees,and the slope of the Warburg impedance of the 3# and 4# sand systems are larger than that of the 45 degree angle.(6)Capacitive arc and the corrosion rate and the particle size is not a linear relationship,when the particles are smaller or larger will make corrosion rate,initial corrosion corrosion rate of 2# sand system minimum,along with the prolonging of corrosion cycle,the corrosion rate increased.The particle size affects the heterogeneity and connectivity of pore structure,and the diffusion process of oxygen and electrolyte solution in the pore structure will influence the corrosion rate.