Role of Fe oxides in corrosion of pipeline steel in a red clay soil

•Red clay soils are especially corrosion aggressive to metallic materials.•Soil Fe oxides stimulate soil corrosion by acting as a cathodic depolarizer.•Layer silicates and Fe oxides are actively reactive in soil corrosion process.•The succession of wet and dry period makes the soil more aggressive.•Fe oxides should be considered in evaluating corrosivity of red clay soils.

Red clay soils show especially corrosive towards metallic materials, but no satisfactory interpretation exists to explain the phenomenon. Soil Fe oxides (goethite, hematite, etc.) appear to play a key role in soil corrosion by functioning as a cathodic depolarizer. A series of experiments were therefore conducted to evaluate the effect of Fe oxides on corrosion of pipeline steel in a red clay soil. The results indicate that corrosivity of the red clay soil greatly relieves after Fe oxides are removed from the soil. A Fe oxide-catalyzed kinetic mechanism is proposed to clarify high corrosivity of red clay soils.