Effects of the Addition of Cu and Ni on the Corrosion Behavior of Weathering Steels in Corrosive Industrial Environments

The effect of Cu and Ni content on the corrosion behaviors of weathering steels in a corrosive atmosphere was investigated using electrochemical measurement techniques, such as electrochemical impedance spectroscopy and linear polarization resistance methods. Scanning electron microscopy with energy-dispersive spectrometry (EDS) and x-ray diffraction (XRD) were used to analyze the samples. The corrosion rates, which are above 2.0 mm a⁻¹ at 48 h and approximately 1.12 mm a⁻¹ at the range of 144-240 h, show that Cu and Ni slowed down the electrochemical reaction at the initial corrosion stage. With an increasing immersion time, the protective properties of the rust layer exhibited an increase in its impedance, and it was enhanced compared to that in the initial stage. The enrichment phenomenon of Cu and Ni elements in the inner rust layer was more evident in the 0.4Cu-0.4Ni and 0.7Cu-0.7Ni steels than that of 0.3Cu-0.3Ni steel after 240 h. The XRD and EDS results show that the inner rust layer contained compositions of CuO and Ni compounds, which filled up the pores located on the corrosion products contributing to the densification of the rust layer.