NDT methods in artwork corrosion monitoring

The interaction of materials with the atmosphere has recently received increased attention. Although the interaction between atmosphere chemistry, weathering and pollutants deposition is complex, there is a need for measuring the surface materials lost through weathering and acid rain by art objects. In fact, data regarding material response to different conditions can be used to predict long-term trends in degradation as well as to assess deterioration process parameters. Conventional inspection techniques, such as ultrasonic measurements or X-ray radiography, can be timeconsuming and/or expensive. In principle, methods to monitor artwork corrosion should have the following features: non-contact nature, fast and inexpensive operations, good sensitivity. In this paper an investigation on detection and monitoring of artwork corrosion by infrared thermography and optical techniques is carried out. In IR thermography, material loss is related to thermal contrast, which is defined as a suitable normalization of temperature differences on the specimen. Optical techniques basically rely on optical contouring, which leads to a 3D map of the surface. Experimental results obtained using simple inversion procedure for IR data are compared with optical results.