Novel approach to correlate degree of surface deterioration to coating impedance for laboratory test panels coated with two types of primers

Abstract

Relationships between deteriorated coating surface conditions of laboratory test panels determined by image processing software and coating impedance data collected with electrochemical impedance spectroscopy (EIS) were investigated. A unique relationship was found between the log |Z|_0·1 values of experimental EIS data and the corresponding deteriorated area ratios determined by the image processing method. A well defined one to one relationship was also found between log |Z|_0·1 values and log (R_po) values extracted through EIS data fitting analysis. This study demonstrates that estimation of log (R_po) at a certain deterioration stage is feasible via field image processing alone without running in situ EIS measurements and going through time consuming EIS fitting analysis. A field coating maintenance program established by this methodology can be an effective tool for bridge maintenance engineers who need to make timely decisions on coating repair/rehabilitation work based on the quantitative ‘visual’ image scan results and ‘invisible’ coating pore resistance.

Keywords:

• Organic coatings
• EIS
• Visual imaging
• Deteriorated area
• Atmospheric corrosion
• Rust