Effects of non-viable microbial film on corrosion of pipeline steel in soil environment

•The roles of product film and microbial film in aerobic corrosion was compared.•Corrosion product and microbial film can enhance aerobic corrosion, respectively.•The enhancing role of corrosion product is indistinct at the end of the experiment.•The acceleration role of the microbial film always exists throughout the experiment. In this paper, the effects of the corrosion product and non-viable microbial film on the corrosion behavior of X80 steel in the aerobic soil solution were studied via electrochemical measurement, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Uniform corrosion dominated the corrosion process of the control coupon, while the local corrosion sensibility of the corrosion products (CP) and microbial film (MF) coupons increased in the same environment. Generally, the original corrosion product on the steel surface enhanced its corrosion rate at the initial stage of the experiment, while the enhancing role decreased at the end of the experiment. The non-viable microbial film on the steel surface intensively accelerated its corrosion rate at the initial stage, and the acceleration role always existed throughout the experiment. The acceleration role of the microbial film may stem from the combined effects of extracellular polymer substance (EPS), Fe oxides and sulfides.