Effect of SRB on Corrosion Behavior of X70 Steel in a Simulated Soil Solution

Abstract

The corrosion behavior of X70 steel was studied in a simulated soil solution with and without sulfate-reducing bacteria (SRB) by means of weight-loss measurement, SEM-EDS analysis and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion rate in- creased with time in the solution without SRB, while the corrosion product film was loose and non- protective. In the solution with SRB, however, a compact and homogeneous biofilm formed on the steel surface, which could suppress the mass transfer so that to mitigate the steel corrosion, whilst the corrosion product film became loose and apt to spall because of the increasing amount of ab- sorbed substance and sulfide in the corrosion product with time, in consequence the corrosion of the steel substrate was further promoted. The stability of the inner portion of the corrosion product film was related to the distribution of deposits on the steel in the solution without SRB. The porous extracellular polymeric substances (EPS) formed on the steel in the solution with SRB played a role in barrier action to the mass transfer during the activated process.