Copper alloy artworks are particularly subjected to chloride attack, which may trigger bronze disease. Therefore, early identification of the phenomenon is crucial in order to stabilize the reactive copper chloride (CuCl) and remove the harmful corrosion products (atacamite and polymorphs). Confocal Raman Microspectroscopy (CRM) has proven to be effective for the detection of small amounts of atacamite, ascribable to the initial phases of corrosion. The handling of bronze artworks is often difficult or even impossible given their large size and weight, and sampling is not always allowed, making the use of portable instruments mandatory for on-site diagnostics. This paper proposes a method for the early detection of corrosion using non-invasive approaches. In this work, we present the results obtained from a set of artificially aged bronze samples with a suite of either laboratory (bench-top) or field (portable/transportable) instruments with the aim of highlighting their characteristics and performances in the diagnosis of bronze disease. Raman spectroscopy, Fiber Optics Reflectance Spectroscopy (FORS), Optical Coherence Tomography (OCT), and Scanning Electron Microscopy (SEM) were applied for chemical and morphological characterization of the samples.

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.