Evaluation of zinc-rich epoxy paint performance by electrochemical impedance spectroscopy

Abstract

To improve understanding of Zn-rich coatings for use in the storage reservoirs of oil, such coatings are being examined in the laboratory by the suite of testing techniques: Open Circuit Potential (OCP) (Ecor) measurements , exposure time to verify electrochemical cathodic protection, electrochemical Impedance Spectroscopy (EIS), Optical Microscopy, local SEM and RAMAN for Zn reaction product ID. These testing techniques are being used in conjunction with a modeling and characterization effort focused on improve understanding of the effects of the metal pigment volume concentration (PVC), particle shape and aspect ratio, particle size and size distribution, as well and particle orientation on coating performance. The single frequency electrochemical impedance spectroscopy (EIS) measurements of impedance as a function of time for Zn-rich primers, or other active systems, gives insights into the evolution of the electrical properties .These primer coatings are usually top-coated to function optimally and have a long field lifetime. When used properly, these primers provide almost as much protection to steel as galvanizing. The coatings system of a Zn-rich primer and an exterior durable topcoat provides both barrier and damage (sacrificial/cathodic) protection to steel substrates

Keywords

• zinc-rich primer, cathodic protection, electrochemical impedance spectroscopy, corrosion mechanisms