Atmospheric Corrosion Behavior of Ni-advanced Weathering Steels in High-chloride Environment: Effect of Ni on Corrosion Morphology

It is well known that Ni-advanced weathering steels considerably improve the protectiveness of rust layers and drastically reduce corrosion rate compared with the conventional weathering steels. However, unpainted Ni-advanced weathering steels are not suitable for use in high-chloride environments because of no formation of protective rust layers. To expand the application of Ni-advanced weathering steels, it is imperative to understand in detail their corrosion behavior in high-chloride environments. In this study, the effect of Ni addition on the atmospheric corrosion behavior of carbon steels was explored through a wet-dry cyclic corrosion test and potentiodynamic polarization measurements in a simulated high-chloride environment. In particular, the study focused on corrosion morphology and analyzed the distribution of corrosion depth after the corrosion test. During the corrosion test, the protective rust layers did not seem to form on all the specimens due to the high-chloride condition. Nevertheless, the corrosion rates decreased with increasing Ni addition to steels. Corrosion morphology analysis revealed that the Ni addition suppressed relatively uniform corrosions on the entire surface and the growth of deep hole-like corrosions. Anodic polarization curves showed that the Ni addition suppressed the dissolution of the steel matrix, which led to the atmospheric corrosion properties of 2.5Ni-WS and 5Ni-WS in inhibiting relatively uniform corrosion and the growth of deep hole-like corrosions. The change in the electrochemical properties of the steel matrix due to the Ni addition significantly affects the atmospheric corrosion behavior of carbon steels in high-chloride environments.