Understanding the role of alloyed Cu and P in the initial rust composition of weathering steel formed in a simulated coastal-industrial atmosphere

Highlights: • Initial atmospheric corrosion of Cu- and (Cu + P)- alloyed weathering steels was comparatively studied. • Cu and P promoted the formation of α-FeOOH in the inner compact rust layer and inhibited the formation of γ-Fe₂O₃/Fe₃O₄. • Corrosion product compositions and distribution were mutually confirmed by SR-XRD and Raman spectroscopy. A combination of SR-XRD, Raman spectrum, EPMA and electrochemical measurements were used to investigate the role of alloyed Cu and P in the initial rust composition of weathering steel formed in a simulated coastal-industrial atmosphere. Results indicated that the addition of Cu inhibits the electrochemical cathodic and anodic process in the corrosion process and is beneficial to the formation of α-FeOOH in the internal rust layer. The addition of Cu and P was more effective in promoting the formation of α-FeOOH and inhibiting the formation of Fe₃O₄/γ-Fe₂O₃, resulting in the lowest corrosion rate.