Five-year atmospheric corrosion of Cu, Cr and Ni weathering steels in a wide range of environments

•Addition of Ni (3.0 wt%) promotes a notable increase in corrosion resistance. To unpainted use:•In ISO C2 atmospheres: all the tested steels.•In ISO C3 atmospheres: the steels alloyed with 0.50 wt% Cr or 3.0 wt% Ni.•In ISO > C3 atmospheres: none of the tested steels. This work considers fourteen weathering steels manufactured by adding Cu, Cr and Ni alloying elements to extra mild steel. The steels were exposed for up to 5 years in different atmospheres. The atmospheric corrosion resistance of the steels was evaluated and the rust layers formed were characterised by X-ray diffraction, optical microscopy and scanning electron microscopy. The addition of Ni, particularly at 3.0 wt%, leads to a notable increase in corrosion resistance. The rusts formed contain lepidocrocite, goethite and spinel phases. X-ray diffraction also detected small amounts of kornelite (industrial atmosphere) and akaganeite (marine atmosphere).