Low-alloy weathering steels resistant to SOx pollution show poor performance in environments where airborne salinity is high. Recent researches on rust and weathering steels, therefore, have been focused on the rusting mechanism in the presence of chloride and development of new steels and coatings for the use in marine/coastal environments. In the paper discussion and literature review are given for the following subjects: 1) tolerable limit of airborne salinity level for the use of uncoated weathering steels in infrastructure, 2) related case study of flake rusting on bridges in coastal area, 3) thermochemical aspect of rusting in chloride environments, 4) crystal structure of iron rust in high salinity, 4) electrochemical reaction of rust and its catalytic properties in chloride media, 5) protective nature of rust of weathering steels, and 6) quality evaluation (or stabilization) of rust on weathering steels.
