Corrosion Rules and Mechanism of High Strength Steel of Q450NQR1
YIN Yuqun1, ZHAO Jinbin1, CHENG Xuequn2, LI Xiaogang2
1. Research Institute of Nanjing Iron and Steel Company, Nanjing 210035, China;2. Corrosion and Protection Center, Beijing Science and Technology University, Beijing 100083, China
Abstract:According to the requirement of Ministry of Railways of China, the strength of steel plate used for railway truck is improved to 450 MPa. Many Chinese steel companies developed their own Q450NQR1, which is a kind of high strength weathering steel containing Cu, Cr, Ni and other alloying elements. For most products, the mechanical properties are excellent; however their atmospheric corrosion resistance is not that good in practical applications, because specialist on corrosion has seldom participated in the developing process of Q450NQR1. The accelerated corrosion properties of high strength weathering steel Q450NQR1 are studied and compared with mild carbon steel Q345B by means of the periodical immersion cyclic corrosion test. The corrosion potential and corrosion current density are analyzed by electrochemical technology. The results show that under the testing conditions, the weight losses and average corrosion rates for steel Q450NQR1 are remarkably lower than that for steel Q345B. The corrosion product formed on steel Q450NQR1 is more stable than that on steel Q345B, and it reached at stable condition after 48 hours. The same conclusions are drawn by the electrochemical polarization test and open potential measured. The EDS and XRD results suggest that Cu and Cr are able to improve the stability of corrosion product formed on steel Q450NQR1, and with the in-creasing contents of α-FeOOH, which provides a better and stable protection from further corrosion of the substrate, the corrosion resistance of steel Q450NQR1 is improved.