Development of monitoring techniques for coatings applied to industrial heritage

This paper presents a new approach for the evaluation of the preventive properties of outdoor protective coatings against corrosion as applied to industrial heritage. The approach relies on the combination of three different analytical techniques: Electrochemical Impedance Spectroscopy (EIS), FT-IR Spectroscopy and Microscopy (both Scanning Electron- and Optical-Microscopy).This work focuses on the preliminary results obtained by EIS carried out with a specially designed contact probe suitable for in field studies on art bronze objects. This measurement method was tested on steel coupons (pre-corroded and on original painted steel), prepared during the CONSIST project1 and protected with different transparent organic coatings in order to compare the effectiveness of their protective behavior after a period of natural aging.The EIS testing procedure is relatively simple and gives quantitative data about the performance of the protective coatings. Nevertheless, the acquired spectra have been interpreted, at present, from a qualitative point of view. The results for the samples before and after exposition allow to distinguish different corrosion behaviors and to describe protective coating failure. Further measurements are on its way; these will aim at achieving a better understanding of the role of iron corrosion products in the protective behavior of organic coatings.Although still at a preliminary stage of the project, the results described in this work show the potential of the EIS technique for the aimed purpose, our ideas in adapting it to the monitoring task and our efforts to combine it into a practical tool in Conservation Science. Preliminary results are reported.