Experimental Study On The Influence Of The Silt Containing Sodium Chloride On The Corrosion And Tensile Strength Of X70 Steel

Because there are many factors affecting the corrosion of underground metals in the soil,the influence of humidity and salt content on the corrosion behavior and tensile properties of silt is not perfect.This paper uses electrochemical impedance technology(EIS),polarization curve technology(PC),indoor tensile test methods and other methods to investigate the electrochemical corrosion behavior and tensile strength of X70 steel in silt with different water and salt content.Research and give a reasonable explanation.The main research conclusions are as follows:(1)The Nyquist diagrams of sodium chloride-containing silt under different water contents are all composed of a part of the arc in the high frequency area and the oblique straight line in the low frequency area.The radius of the arc becomes smaller as the water content and salt content increase.The equivalent circuit of sodium chloride-containing silt is established: as the water content and salt content increase,the silt's own resistance and charge transfer resistance decrease,and the constant phase angle element increases;while the electric double layer capacitance increases with the increase in water content and salt content.The increase in salt content increases,and the decrease in water content decreases.(2)The corrosion products,corrosion area and depth on the surface of X70 steel increase with the increase of water content and salt content;when the water content is low,the surface corrosion area of X70 steel is relatively small,and as the water content increases to at 22%,the corrosion area and depth of X70 steel reach the maximum,and then as the water content further increases to 26%,Then as the water content further increases to 26%,the depth of the corrosion zone of X70 steel becomes shallower.(3)The capacitive resistance arc of the Nyquist diagram of X70 steel in silt systems with different water and salt content decreases first and then increases with the increase of water content and salt content,and the resistance value first decreases and then increases,The bonding layer resistance and the charge transfer resistance first decrease and then increase,and the corrosion rate first increases and then decreases;when the embedding time is 90 days,the diffusion resistance appears in the Nyquist diagram of X70 steel.(4)The polarization curves of X70 steel in the silt system with different water content and salt content are similar in appearance and are smooth and continuous.Under the same salt content,as the water content increases,the self-corrosion potential of the electrode continues to move negatively,the self-corrosion current density first increases and then decreases,and the corrosion rate first increases and then decreases.Under the same water content,as the salt content increases,the self-corrosion potential of the electrode continues to move negatively,the self-corrosion current density first increases and then decreases,and the corrosion rate first increases and then decreases.The three factors of soil moisture,air content and salt content both alternate and influence each other.When the salt content is too high,the solubility of oxygen decreases,which reduces the corrosion rate.(5)Through the tensile test of the X70 steel stretching test,the same amount of salt,with the increase of water,the corrosion area of the X70 steel stretching test is increasing,but the depth of corrosion is too high.When it is,it is lighter;the tensile strength of X70 steel increases after the increase of water content is reduced.Under the same water content,the tensile strength of X70 steel increases after the increase of salt amount is reduced.