The Study Of Corrosion Law Of Metal Material Buried In Contaminated Soils

Soil corrosion is an important part of metal corrosion in natural environments. It's necessary and significant to investigate the corrosion behavior and law of metal materials in soil. Soil is a complex system containing gas, liquid and solid. There are micro cell corrosion and macro cell corrosion in soil. The salt, moisture, gas content, acidity, microorganism, organic matter, and weather condition all affect soil corrosion. Moreover, these factors often interact with each other and they are changing along with time. Recent years, as the apace development of industrial,soils are contaminated more and more seriously。Northeast region is the important old-industrial base,many petroleum,petrochemical,refinechemical,steel metallurgical,electric power,coal mine,machinemaking manufactories paper mills and spinning mills lied there. More and more liquid waste and solid rubbish are throwed into nature from these factories and deteriorate the soils, and contaminated soils make favored conditions for metal corrosion. As most domestic scientists mainly studied in not contaminated soil corrosion, and few study about the contaminated soil corrosion has been taken. A lot of work about contaminated soil corrosion has been taken in foreign countries. As the manifolding of contaminated soil types and contaminated severity, it's necessary to study the corrosion law of metal in multifarious contaminated soils.The effects of polluted ingredients (mainly organic detergents), microorganism (SRB), and pH value on metal corrosion were studied by electrochemical impedance spectroscopy (EIS), polarization curve, scanning electron microscope (SEM), mass loss in present paper. The effects of SRB on macrocell corrosion of Q235 steel also was studied in this paper. The main results are as followings:The influencing of sulfate-reducing bacteria (SRB) to metal corrosion is evidently in contaminated soils. The existing of SRB accelerates the equality corrosion rate of metal. Propagating and metabolizing of SRB can produce organic acid to can loosen the corrosion product film, and accelerate the metal corrosion.Soil have intensively buffer capacity, it's difficult to change pH value of it, even very low pH value acid solution. When pH value of soil changed from 4.5 to 3.5, as different corrosion mechanism, at first corrosion rate reduce and then increase when pH value under 4.0.Corrosion rate of metal arrive at lowest value when pH value of contaminated soil is 4.0.The effects of detergent to corrosion rate of metal in contaminated soils are complicated. In one side, as the absorption of detergent on metal superficial blocked oxygen, corrosion rate can be reduced. In another side, detergent make favored condition for SRB and accelerate corrosion rate. When the content of detergent is low, absorption is dominant and corrosion rate is reduced. As the increasing of detergent content, the accelerating ability of detergent is more and more evidently.As the effect of SRB, the cathode and anode of macrocell reversed at the first days. When stabilized of macrocell, the precathod is anode, and preanode is cathode. The current density of macrocell is negative value at first days and then become positive value. As the increasing of buried times current value enhanced at first and then receded and stabilized at some value. The ratio of cathode area to anode area of macrocell also have evident affect on corrosion rate. The corrosion rate increased as the ratio enhanced. The corrosion rate of macrocell anode is bigger than natural metal corrosion rate in the same contaminated soils, and the corrosion rate of macrocell cathode rate is smaller than natura l metal corrosion rate in the same conditions.