The influence of rare earth elements lanthanum on corrosion resistance of steel plate for offshore platform

Abstract

Two kinds of offshore platform steels without rare earth elements and with trace rare earth elements lanthanum (less than 20ppm) were selected as the research objects. The corrosion of the two groups of steels was simulated by salt spray corrosion chamber. The macro/micro corrosion morphology of the two groups of steels was studied by scanning electron microscope; The periodic immersion corrosion experiment was used to accelerate the corrosion, the weight loss method was used to study the corrosion kinetics, and the morphology of corrosion rust layer was observed by scanning electron microscope; The composition and content of corrosion products were analyzed by XRD; The electrochemical behavior of the steel after corrosion was analyzed by electrochemical polarization curve and Nyquist diagram. The results show that the addition of trace rare earth elements lanthanum (less than 20ppm) can reduce the corrosion rate and corrosion current of two kinds of offshore platform steel with different strength, and the corrosion layer is more compact, which is a corrosion product with protective performance α - FeOOH increased. The addition of trace rare earth elements lanthanum (less than 20ppm) improves the corrosion resistance of two kinds of offshore platform steels with different strength.

Keywords

• offshore platform steel
• trace rare earth elements
• salt spray corrosion
• immersion corrosion
• electrochemical corrosion