Abstract
A polarization study on polished, rusted and phosphated steels with various painted surfaces has been made in 3% NaCl aqueous solution at 25°C. With oil painted steels, icorr increased sharply after a certain time (critical time) and electrical resistance decreased at the same time. The shorter the critical time and the time for electrical resistance to reach 105ohm/40cm2, the larger the rusted and blistered surface area in the salt spray test becomes. With zinc rich-epoxy painted steels, however, icorr increased and electrical resistance decreased gradually with time also. In conclusion, the corrosion resistance of oil painted steels can be estimated from icorr and electrical resistance values which show a good correlation with the results of the salt spray test and the immersion test. In general, the corrosion resistance of rusted-painted steels cannot be estimated well from the tan δ value at an initial stage of immersion.
