Defect Detection in Conformal Organic Coatings of Metal Foils by AC Impedance
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
A method of testing organic coatings on metal foils involves AC impedance measurements of the metal-coating-solution interfacial region of a sample submerged in an electrolyte solution. The described technique yields a quickly obtained, non-destructive, quantitative electrochemical parameter which is proportional to the defect area in a conformal organic coating of a metal foil. The method works as follows. At a given AC frequency, the interface will show an impedance corresponding to resistive, capacitive or a combination of these properties [*]. Generally, at a sufficiently high frequency all current will cross an interface as capacitive current, while at a sufficiently low frequency only resistive (faradaic) current will pass.