A Research On The Effects Of Pesticide And Fertilizer On Microbal Corrosion Of Underground Metal

Sulfate reducing bacteria (SRB) is an important cause of microbial corrosion ofmetal buried in soil. The inhibition technology of microbial corrosion has become animportant research direction at home and abroad. The microbial corrosion law of carbonsteel buried in soil with SRB or not and different concentrations of imidacloprid orpotassium dihydrogen phosphate has been studied in this paper, using microbial analysismethod, weight loss, polarization curve, electrochemical impedance spectroscopy,scanning electron microscopy and surface energy spectrum method, and the soilhumidity on the effects of microbial corrosion in soil with potassium dihydrogenphosphate have been discussed in this paper.Under the condition of adding imidacloprid alone, either in a bacterium or sterilesoil, with the increasing of imidacloprid concentration, the soil redox potential, Q235steel corrosion potential and the impedance capacitive arc radius increased, and theincreasing trend had been maintained to the end of the experiment, which show that thecorrosion rate of Q235steel decreased with imidacloprid concentration increasing,indicating the presence of imidacloprid slowed down the corrosion rate of Q235steel.Under the same conditions, the corrosion potential of Q235steel in bacteria soil waslower than that in sterile soil, which indicates the presence of SRB accelerated thecorrosion rate of Q235steel buried in soil.Under the condition of adding potassium dihydrogen phosphate alone in sterile soil,with the increasing of potassium dihydrogen phosphate concentration, the soil redoxpotential, Q235steel corrosion potential and impedance capacitive arc radius increased,indicating the presence of potassium dihydrogen phosphate slowed down the corrosionrate of Q235steel in this condition. It is in accord with the effect of imidacloprid oncorrosion of carbon steel. However, compared with in bacterium soil under the samecondition, the soil redox potential, Q235steel corrosion potential and impedance capacitive arc radius firstly decreased and then increased, which mean that the presenceof potassium dihydrogen phosphate accelerated the corrosion rate of Q235steel buriedin SRB soil firstly and then slowed down. Under the same conditions, the corrosionpotential and impedance capacitive arc radius of Q235steel in SRB bacteria soil weresmaller than that in sterile soil, which show that the presence of SRB accelerated thecorrosion rate of Q235steel buried in soil.In order to study the effect of soil humidity on the results of experiments, theexperiments of soil adding potassium dihydrogen phosphate alone in different soilhumidity (soil humidity were15%and20%, respectively) were carried out. The resultsshow that the humidity had a certain influence on the corrosion of Q235steel under thesame conditions, and the impedance capacitance arc radius of Q235steel in humidityfor20%soil was larger than that in15%soil, which means that the increasing of soilhumidity would slow down the corrosion rate of Q235steel.This research results show that both insecticide imidacloprid and fertilizerpotassium dihydrogen phosphate, in a certain concentration, could suppress the SRBcorrosion of Q235steel. With the increasing of soil humidity, the inhibitory effect wasmuch more obvious.