Insight on corrosion behavior of a Cu–P–Cr–Ni steel with different Ni contents by electrochemical and periodic immersion corrosion experiments

Corrosion behavior of Cu–P–Cr–Ni weathering steels with different nickel contents was studied by periodic immersion corrosion test for 72 h. The mass loss method was used to evaluate the weatherability of weathering steel. The rust layers formed on weathering steel were characterized by scanning electron microscopy, X-ray diffraction, electron probe microanalysis, X-ray photoelectron spectroscopy, and electrochemical measurements. The results of periodic immersion corrosion test for 72 h showed that the mass loss rates of Cu–P–Cr–0.14Ni steel and Cu–P–Cr–0.04Ni steel were 1.57 and 1.61 g/(m² h), respectively. According to the electrochemical experiment, the corrosion potentials of the two tested steels at the initial stage of corrosion were − 0.6852 and − 0.7037 V, respectively. With the corrosion time reaching 72 h, the corrosion potential difference between the two tested steels was gradually reduced. In the initial stage, NiO was formed in the rust layer and can dramatically promote the crystallization of corrosion products to improve the stability of the rust layer. After periodic immersion corrosion test for 72 h, Ni element had no obvious effect. At this time, it was mainly the enrichment of Cu and Cr elements in the form of CuO and Cr₂O₃ in the rust layer that could further protect the matrix.