Résumé : Corrosion of X52 pipeline steel under a thin layer of soil solution containing sulphate-reducing bacteria (SRB) was investigated under various gassing conditions (i.e., air, nitrogen and 5% CO2). In the sterile solution, the steel suffers from the highest corrosion rate upon air-purging. In the presence of SRB, the steel corrosion is affected by the aeration of the solution layer. While the oxygen inhibits the bacterial growth, the SRB growth and biofilm formation are enhanced in the presence of CO2, accelerating the steel corrosion. There is a synergism of SRB and CO2 on the steel corrosion.