Studying inhomogeneity of organic coatings using wire beam multielectrode and physicomechanical testing

Abstract

The effect of thickness, curing temperature and solvent on the structural inhomogeneity of several types of organic coatings has been investigated. The local distribution of electrochemical resistance was studied using a wire beam multielectrode array, while the inhomogeneity at a larger scale was examined using ,3 cm 2 area detached coatings. Physicomechanical tests were also employed to address the structural changes occurring because of variation in curing temperature and the type (or absence) of solvent. Results acquired by wire beam electrode and from the detached coatings showed that increasing the thickness and curing temperature improves the homogeneity of the coating as does elimination of solvent. Waterborne coatings exhibited a relatively homogeneous low resistance with a resistance lower than the threshold required for effective corrosion protection. Results of physicomechanical examination suggest that unreacted functional groups and water absorption are of the main causes of formation of structural defects in organic coatings.

Advances in corrosion protection by organic coatings: What we know and what we would like to know

“…It was believed that water uptake into the film controlled the "I" type conduction whereas ion uptake into the film controlled "D" type conduction. More recently Jamali and Mills studied the electrical properties of coatings using the wire beam electrode at millimetre spatial resolution 8 and concluded that the majority of film area was of "I" type.…”

Analysis of electrochemical noise measurement on an organically coated metal

“…Saturated calomel electrode (SCE) was used as reference electrode in all experiments. Resistance value of coatings was defined prior to testing using a DC electrometer in a two electrode arrangement with a single U-cell and two SCEs (for details see reference [34]). Noise measurement was conducted at 2 Hz sampling frequency with a total of 512 data points collected in 256 seconds.…”

A probabilistic model for estimation of ionically permeable inhomogeneities in polymer coatings

“…The SCE impedances, typically in the order of 10 4 ohm is negligible compared to high impedance of organic coatings and therefore considered insignificant. This method of impedance measurement has been used and described in the literature a number of times [14,25,34]. The DC resistance was measured with first 1 mM KCl and then 3.5 M KCl solutions to identify the conduction type of each piece.…”