The presence of AC may cause serious damage on metallic structures even when cathodic protection
is applied and off-potential matches –0.85 V CSE criterion. Uncertainties still exist on protection
potential interval and on protection current density to reach an acceptable protection when AC
interference is present. In order to investigate these aspects, weight loss tests on cathodically protected
carbon steel specimens were performed in laboratory in soil simulated conditions in presence of AC,
with densities ranged from 10 to about 500 A/m2, to assess cathodic protection criteria as AC density
threshold and protection potential.