Atmospheric Corrosion of Different Steel Types in Urban and Marine Exposure

The aim of the present work is to study the atmospheric corrosion behavior of metals exposed to both urban (Milan, IT-Lombardia) and marine (Bonassola, IT-Liguria) atmospheres in Italy. A number of coupons (100 × 150 mm) of carbon steel (CS), hot-dip galvanized steel (GS) and different grades of stainless steel (SS) were exposed. At fixed periods of time, samples were characterized by means of Linear Polarization Resistance (LPR), mass loss tests and corrosion product analysis. The corrosion rate on carbon steel exposed to an urban atmosphere, obtained by means of mass loss tests and LPR, are in good agreement with the value estimated by the dose-response function according to the ISO 9223 standard. The yielded results can be classified in corrosivity class C2 of the same ISO 9223. Similar measurements on galvanized steel exhibited a coherent average corrosion rate. Higher corrosion rates were measured for samples exposed to a marine atmosphere for both materials, with values belonging to exposure classes C4-C5 for both materials. Stainless steel samples exhibited only superficial staining in the case of marine exposure, even after just a few months.