Foul-control paints behavior near anodes of Impressed Current Cathodic Protection systems

It is known by foul control paint and Impressed Current Cathodic Protection system producers that paints can fail in proximity of the anodes. This failure is well known in industrial field, but does not represent a structural problem. As a matter of fact, paint recovery is performed within routinary docking operations. Within this framework, it is interesting to evaluate the behavior of new generation biocide-free foul control paints under a chemical stress resembling that near ICCP anodes, where seawater turns acidic and chlorinated. Data in this area have not been already studied nor published. The values of free chlorine and pH produced at anodes, to which paints are exposed, were obtained experimentally. Two biocide free paints, a foul release (FR) and an amphiphilic self-polishing (SP), were chosen for testing on these conditions. Paints were exposed to a 3x3 matrix of 'pH/free-Cl' different conditions. After 3 months of immersion in the selected environments, a physical-chemical characterization was performed through: visual inspection, detachment area analysis, thickness variation, contact angle variation, profilometry and IR. Laboratory and field tests were finally performed to evaluate the foul-control properties after treatments. Results showed that the degradation is mainly induced by free chlorine oxidation, and acidity strengthens the chemical attack. Both paints in the harshest condition were disbonded. Foul release paint seems generally more stable but detaches easily from the primer, while the amphiphilic SP is apparently less prone to detachment from the primer, but exhibits modification of its physical properties. Foul-control properties did not show a substantial drop after the conditioning treatment, but the tests reported detachment of both paints in conditions in which it was not previously observed.