Development and characterization of flexible electrodes for protective painting monitoring

Abstract

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.

An in situ investigation of the corrosion behaviour of a weathering steel work of art

“…The water penetrates the pores overcoming the reduced gel mobility without exposing the samples to corrosion hazards. This way, if the measurement is performed after the gel electrode has been positioned on the preconditioned surface for 30 min, the electrode behaves similarly to traditional electrochemical cells behaves similarly to traditional electrochemical cells . On each measuring area three electrodes have been positioned in order to assess the corrosion layer stability and the measurement reproducibility.…”

“…The impedance measurements were carried out by means of a portable equipment specifically designed by the authors to work in the field. [13] The instrument is battery operated and can work either as a stand-alone device, storing the results into its memory, or in conjunction with a personal computer to observe the impedance traces as the measurement proceeds. It is capable of measuring impedances in the range 1 kΩ-10 GΩ and works in the frequency range 10 mHz to 40 kHz.…”

Noninvasive Solution for Electrochemical Impedance Spectroscopy on Metallic Works of Art

“…Unfortunately, really soft materials can only be created by generating a foam structure, which tends to have a non-uniform surface with consequent risk of the electrode surface roughness reducing the effective contact area i.e. the area of the electrode which is actually in contact with the specimen [13]. Two kinds of materials were tested: a rubber material, which shows a compact surface and a Young modulus of about 3 MPa, and a low density closed-cell polyurethane with a Young modulus of about 0.3 MPa.…”

“…Once the electrodes had been prepared, tests were performed to assess their behavior, as a function of the load pressure, which both changes the mechanical dimension and the effective contact area [13]. To this aim, tests were performed by using a diamond-like carbon (DLC) coated disk [14] of known coating thickness and dielectric constant.…”

“…To this aim, tests were performed by using a diamond-like carbon (DLC) coated disk [14] of known coating thickness and dielectric constant. The measurements were performed with a cell on which it is possible to adjust the load pressure in the range of 10 kPa, corresponding to an almost undeformed electrode, to 180 kPa, corresponding to a very deformed electrode [13]. Fig.…”