Atmospheric corrosion of Ni-advanced weathering steels in a marine atmosphere of moderate salinity: 10 years of exposure

Abstract

Three Ni-advanced weathering steels, with nominal nickel contents of 1 %, 2 %, and 3 wt%, respectively, along with a copper-bearing steel, all manufactured using the electroslag remelting technique, were exposed for 10 years to the pure marine atmosphere of Cabo Vilano in north-west Spain (Camariñas, A Coruña), with an average chloride ion deposition rate of 20.4 mg/m²day. The corrosion curve as a function of exposure time was obtained, yielding actual values of the exponent n from the power-law model. Rusts formed on the steels were quantitatively analyzed using the Rietveld refinement method applied to X-ray diffraction (XRD) data, Mössbauer spectroscopy, SEM/EDS, and BET surface area measurements. The crystallite size of the iron oxyhydroxides present was determined from XRD line broadening using the double-Voigt approach, and the average particle size was also estimated by Mössbauer spectroscopy. The corrosion rate decreased with increasing nickel content in the steel composition, although no significant differences were observed beyond 2 wt% Ni. The amount of goethite quantified by Mössbauer spectroscopy was higher in the nickel-containing steels compared to the values obtained by XRD. Moreover, the amount of superparamagnetic (nanosized) goethite determined by Mössbauer spectroscopy also increased with nickel content.