Corrosion behavior of API X70 microalloyed pipeline steel in a simulated soil solution in the absence and presence of aerobic Pseudomonas species

Abstract

In this study, the effect of Pseudomonas bacterial species on the corrosion behavior of API X70 microalloyed pipeline steel is evaluated in a simulated soil solution at different immersion times (varying from 24 h to 504 h) under both abiotic and biotic conditions. The electrochemical impedance spectroscopy (EIS) results show a considerable variation in charge transfer resistance of corrosion reaction in the both abiotic and biotic systems. Whereas formation of a protective layer of corrosion products accumulated on the metal surface in the abiotic condition increases the corrosion resistance considerably, the appearance of high concentration of ferric oxide and phosphide-base compounds on the surface causes a deleterious influence on the corrosion rate. The results also show that in the biotic media, accumulation of aerobic Pseudomonas sp. on the metal surface improves the corrosion resistance, while the growth of extracellular polymeric substances (EPS) in metal/biofilm interface at longer exposure times tends to diminish resistance to corrosion. In addition, the extensive localized corrosion has occurred beneath the colony of Pseudomonas sp. biofilm in the biotic media due to an aggressive area in the metal/corrosion products interface.