Exploring the Corrosion Behavior of Low-Ni Cu-P-Cr-Ni Weathering Steel with Different P Contents in a Simulated Atmospheric Environment

The corrosion resistance and influence mechanism of P in low-Ni Cu-P-Cr-Ni weathering steels were analyzed by wet/dry cyclic corrosion and electrochemical tests. The electrochemical experiment results showed that the corrosion potential and impedance of weathering steels were all more positive than that of ordinary Q345B carbon steel. Compared to Cu-0.02P-Cr-Ni steel, however, the corrosion current density of Cu-0.07P-Cr-Ni steel was higher. After 72 h wet/dry cyclic corrosion tests, the corrosion resistances of the two weathering steels were nearly identical but better than that of Q345B steel. The effect of P was particularly significant in the initial stage of corrosion. Phosphates (PO 4 3− ) were formed from P, which improved the corrosion current density and promoted the rapid formation of a rust layer. After 72 h wet/dry cyclic corrosion tests, the matrix was further protected by the enrichment of Cu and Cr, which existed as Cu + and Cr 3+ , respectively. The P content did not significantly affect the corrosion resistance of weathering steels after 72 h wet/dry cyclic corrosion tests. Therefore, the P content can be lowered to reduce the cold brittleness in low-Ni Cu-P-Cr-Ni weathering steels.