IMPEDANCE STUDY OF THE EFFECT OF A THIN RUST LAYER AT THE STEEL-PAINTINTERFACE ON COATING DETERIORATION

Impedance measurements were used to study the effect of the presence o f a lightly prerusted substrate on coating deterioration during exposu re to a saline solution. For this purpose, a chlorinated rubber coatin g was applied over clean and prerusted low carbon steel plates. An imp ortant number of replicate specimens were tested to establish the real ity of small differences in the impedance behavior of the paint coatin g. Although individual data were poorly reproducible across the differ ent replicate specimens, statistically significant differences between the average values of paint capacitance and paint resistance for clea n and rusted substrates were shown.