Effect of Microstructures on Corrosion of X80 Pipeline Steel in an Alkaline Soil

Abstract

The influence of microstructures with different heat treatments to stimulate the weld fusion zone and HAZ on corrosion properties of X80 pipeline steel was investigated in alkaline sand soil using electrochemical measurement and surface analysis(SEM, EDS and XRD). The results showed that the microstructure of X80 steel affected the properties of corrosion product layers. Generally, X80 steels with heat treatments had a higher corrosion rate than the as-received steel. The increase of pearlite content enhanced the corrosion of ferrite through a galvanic effect. The appearance of upper bainite and martenite increased further the activity of the steel. The corrosion product layer formed on as-received X80 steel was compact and complete, provided an effective protection to the underneath steel. However, the corrosion product layers on the heat-treated X80 steels were generally inhomogeneous, loose, porous and defective, and provided minor protectiveness. The cathodic/ anodic reactions of X80 steel are dominated by the oxygen reduction and formation of iron oxides that deposit on the steel surface which was through a physical block effect to afford the protection. We shall be able to publish your paper in electronic form on our web page http://www.scientific.net, if the paper format and the margins are correct. Your manuscript will be reduced by approximately 20% by the publisher. Please keep this in mind when designing your figures and tables etc.