Experimental Study On Mechanical Properties Of Lead Nitrate Contaminated Silt And Its Effect On Corrosion Of X70 Steel

The rules of changing in which the influence of the content of Pb ions on the mechanical properties of lead nitrate contaminated silt were researched by the tests on shear strength and compression of lead nitrate contaminated silt. The corrosion of X70 steel in lead nitrate contaminated silt silt was studied by using electrochemical testing technology for polarization curves (PC) and electrochemical impedance spectroscopy (EIS) of the corrosion of X70 steel in lead nitrate contaminated silt. The results offer reference to the research and application on the effect of lead ions on properties of the contaminated silt and corrosion of steel in contaminated silt.It found that dry density of lead nitrate contaminated silt is greater than the uncontaminated silt as a whole, and the dry density of lead nitrate contaminated silt increases then decreases with the content of lead ions increases, by testing dry density of contaminated silt silt with different lead nitrate content.Also, compressibility and shear strength of lead nitrate contaminated silt was tested through the indoor compression test and direct shear test test, with analysis of compression curve (e-p) and shear strength curve (τ-δ), compressibility, shear strength, cohesion and internal friction angle value was calculated. Studies showed that due to generation and decomposition of lead oxide hydrate, decreases of electric double layer’s thickness and decomposition effect of lead ion on silt particles, the shear strength, cohesion increases then decreases, internal friction angle decreases then increases with the content of lead ions increase; void ratio decreases with consumption of pore water and air gap gas, the formation of lead oxide hydrate enhances the overall stiffness of the silt, and compressibility decreases at first; then lead oxide hydrate began to decompose and a large number of cations made the silt particles with a positive charge generate a repulsive force with the increase of lead ion content, compression coefficient became larger again.Through Tafel fitting of polarization curves (PC) of X70 steel in lead nitrate contaminated silt and equivalent circuit simulation analysis of electrochemical impedance spectroscopy (EIS), combined graphics trend of polarization curves (PC) and electrochemical impedance spectroscopy (EIS), it inferred that since content of lead ion incresed, self corrosion potential (Ecorr) shifted positively then shifted negatively, corrosion rate (rcorr) reached the minimum value at days 7 or 14, resistance of corrosion product (Rf) reached maximum value, capacitor of corrosion product film (C) reached the maximum, arc radius of electrochemical impedance spectroscopy at high frequency capacitive reached the maximum, the part at high frequency transformed from arc on days 3 to inclined straight line on days 7, and Slope increased with the increased of lead ion content.It showed that mechanical properties of contaminated silt and corrosion behavior of X70 steel are both affected by the content of lead ion, since change trend of dry density (ρd), anti shear strength (τ), polarization curves(PC) and electrochemical impedance spectroscopy (EIS) of lead nitrate contaminated silt all base on lead ion content of 0.2% as a turning point, lead ions in contaminated silt fully utilizes its characteristics as amphoteric metal.