Effects of Cr Addition on Corrosion Resistance of Thin-wall High Strength Pile Pipe Steels

Effects of Cr on corrosion behavior of thin-wall high strength pile pipe steels were studied with electrochemical test, half-immersion, SEM and EDS. The results showed that the specimens were activated in 3.5% NaCl solution, the corrosion current density reduced with the increase of Cr while the charge transfer resistance increased. The most serious corrosion area of thin-wall high strength pile pipe steel specimens in half-immersion tests was the interface between NaCl solution and air. Corrosion resistance of the specimens was improved with the increase of Cr content. The specimen with 2% Cr had the best corrosion resistance, and the corrosion rate was 0.0234mm/a. Cr element was enriched in the rust layer in different ways at the immersion area and the interface area between NaCl solution and air. Cr was enriched in the inner area of rust layer contacting with the substrate at the immersion area, while enriched in the outer area of rust layer at the interface area between NaCl solution and air.