Impedance spectroscopy monitoring of a polyurethane coating on mortar exposed to NaCl solution

Polyurethane coated OPC mortar specimens exposed to 1M NaCl solution were s tudied by impedance spectroscopy and SEM over a period of 4 years. Results showed a rapid reduction of the coating resistance over the first half year , followed by a slow decrease thereafter. The coating deteriorated starting from the surface in contact with the NaCl solution and the deterioration f ront reached the coating/substrate interface after around three years. Diff erent stages of deterioration were clearly identified by impedance spectros copy. The study demonstrates that impedance spectroscopy is a versatile and informative non-destructive method to assess and monitor the performance o f surface treatments on concrete. (C) 2000 Kluwer Academic Publishers.