Influence Of Sulfate Reducing Bacteria On Corrosive Electrochemical Behavior Of Copper Alloy

In the industry recirculation water system, Sulfate Reducing Bacteria (SRB) is one of the main factors which lead to Microbiologically Influenced Corrosion (MIC). SRB was isolated and purified from the industry recirculation water system to study physiological and ecological characteristic of SRB. The morphological character of SRB was analyzed by SEM.The relationship between growing characteristic and ecological factor of SRB was studied, thus providing theoretical basis for the study of SRB control technique pointedly. The SRB population liked to grow in moderate temperature. Its optimum temperature was 30℃ and its ecological amplitude is from 20℃ to 50℃. The optimum pH is 7 and SRB grows well when pH is 7⁸.With the increase of COD/SO₄^2- in culture media, the sulfate reducing ration became large.Effects of SRB on corrosion behavior of HSn70-1A,HSn70-1B,HSn70-1AB, BFe30-1-1 copper-alloy were studied by electrochemical, microbiology and surface analysis methods. The results showed that the free corrosion potential of the alloy shifted negatively when SRB was inoculated, the polarization resistance decreased obviously, which corresponds to an increased corrosion rate. The serious pitting corrosion occurring on the alloy surface under the action of SRB was observed by SEM. Furthermore, influence of medium flow characteristic and material surface appearance on corrosion behavior of HSn70-1A,HSn70-1B,HSn70-1AB,BFe30-1-1 copper-alloy under the biofilm of SRB were researched. It was showed that the average corrosion rate was higher and the SRB count in the biofilm was less when test piece was immersed in the flowing batch culture medium inoculated with SRB than in the static batch culture medium inoculated with SRB. Thus the flow of medium could speed up the corrosion rate. After being coated in the mixture corrosion inhibitor of MBT and BTA beforehand, the copper electrode had more positive free corrosion potential and higher linear polarization resistance in the culture medium inoculated with SRB than the one without being coated, which demonstrated that the resistance of HSn70-1A, HSn70-1B,HSn70-1AB, BFe30-1-1 copper-alloy against microbiologically influenced corrosion increased obviously.Synergistic effect of HEDP,ATMP and TTA on corrosion inhibition of HSn70-1A and B30 copper-alloy in the industry recirculation water inoculated with SRB was studied by means of electrochemical impedance spectroscopy (EIS) technique,weight loss method and electrochemical polarization. It had been found that there was a synergistic effect between HEDP,ATMP and TTA. The corrosion inhibiting mechanism of HEDP,ATMP and TTA was investigated. The results showed that the corrosion rate of copper -alloy descended with the enhancement of the concentration of corrosion inhibitors. Its adsorption isotherm was investigated. The results indicated that the inhibition followed the Langmuir adsorption isotherm and had good corrosion inhibition capability.