In situ capacitance measurements for in-plane water vapor transport in paint films

A capacitance technique has been adapted to study in-plane water vapor transport in paint films. The technique requires an application of electrical contact materials on the paint film surface for capacitance measurements by electrochemical impedance spectroscopy (EIS). The capacitance obtained by EIS using Cu tape and Ag paste as the contact materials are presented. A direct comparison of capacitance and gravimetric measurements demonstrates that the change in the coating capacitance is quantitatively correlated with the total amount of in-plane water vapor transported in paint films. The water vapor diffusion coefficient derived from the capacitance technique agrees with one from the gravimetric method.

► A capacitance technique for studying in-plane water vapor transport in paint films has been demonstrated.
► Solid metal (Cu foil) electrodes are preferred to metal (Ag) paste electrodes as contact materials for paint film capacitance measurements.
► The change in the film capacitance is quantitatively correlated with the total amount of in-plane water vapor transported in paint primer films.
► The water vapor diffusion coefficient derived from the capacitance technique agrees with one from the gravimetric method.