Development and characterization of flexible electrodes for protective painting monitoring

The assessment of the protective capabilities of thin films is usually performed by means of Electrochemical Impedance Spectroscopy (EIS) and accelerated aging tests in aggressive environments. Typical EIS tests are performed either using electrochemical cells whose electrolytic solutions irreversibly damage the coating or metallic sputtered electrodes which cannot be removed after the measurement. This paper describes a solution that does not employ either chemical solutions or sputtered or mercury electrodes and therefore does not damage the coating and does not pose health hazards. The proposed solution is based on the use of soft rubber electrodes, coated by a thin gold layer. Such electrodes overcome the problems of following the small surface irregularities that would prevent the correct estimation of the contact surface in the case of rigid electrodes. The use of soft electrodes requires a suitable modeling to take the electrode surface roughness into account as a function of the electrode contact pressure. The paper describes the soft electrode development and their modeling and characterization by comparison with mercury and metallic electrodes sputtered onto the surface.