Cathodic protection condition in the presence of AC interference

  • A. Brenna
  • L. Lazzari
  • M. Pedeferri
  • M. Ormellese


To assess cathodic protection criteria in the presence of alternating current (AC) interference, weight loss tests
on cathodically protected carbon steel specimens were performed in soil-simulated conditions in the presence
of AC densities ranging from 10 to about 500 A/m2. Tests last for four months. Carbon steel potential was
periodically monitored by means of a Luggin capillary in order to eliminate the ohmic drop contribution and to
record the true polarization level of the polarised carbon steel samples. At the end of the test weight loss was
evaluated. On the basis of the results, a corrosion risk map is proposed. Main conclusion is that overprotection
is the most dangerous condition in the presence of AC interference.