Non-Invasive Evaluation of Polymeric Protective Coatings for
Metal Surfaces of Cultural Heritage Objects: Comparison of
Optical and Electromagnetic Methods

Year: 2022

Authors: Quintero Balbas D., Dal Fovo A., Porcu D., Chaban A., Porcinai S., Fontana R., Striova J.

Autors Affiliation: National Research Council—National Institute of Optics (CNR-INO), Largo E. Fermi 6, 50125 Florence, Italy;

Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia 3-13,
50019 Sesto Fiorentino, Italy;

Center for Colloid and Surface Science, University of Florence, Via della Lastruccia 3,
50019 Sesto Fiorentino, Italy;

Laboratorio Scientifico, Opificio delle Pietre Dure–MiC, Viale F. Strozzi, 1, 50129 Firenze, Italy

Abstract: The application of protective coatings is an effective preventive strategy to avoid metal
corrosion. Constant monitoring of the coating’s quality is fundamental for the successful preservation
of the metallic objects by reducing their interaction with corroding agents. Their evaluation over time
helps to identify failure at early stages and promote their removal and substitution. Several methods
have been employed for coating evaluation (i.e., chemical analysis, thickness and homogeneity
investigation). In this paper, we compare three methods—Optical Coherence Tomography (OCT),
Confocal Raman Microspectroscopy (CRM), and Eddy Currents (ECs)—to evaluate thickness values
and coating integrity. The results from the two optical techniques (CRM and OCT) agree, being able
to detect the inhomogeneity of the layer on a micron scale but requiring correction to account for the
refraction phenomenon. The Eddy Current is a fast and efficient method for thickness estimation,
providing data with millimetric lateral resolution.


Volume: 12      Pages from: 7532  to: 7544

KeyWords: protective coatings; cultural heritage; OCT; Confocal Raman; Eddy Current;metallic surfaces