engleski

Homogeneity study of modern bronzes for artistic castings using PIXE and PLP

Metal casting is the most efficient way of shaping metals both for industrial purposes, as well as in art modeling. However, when casting an art model in metal, focus is on shape and form, and quality of a cast is often neglected. Therefore, artistic casts may vary in composition and structure, and often exhibit poor homogeneity. Inhomogeneity in composition decreases mechanical properties of a cast alloy, and also has a negative affect on corrosion resistance of alloy due to formation of anodic and cathodic places. These can lead to very dangerous local (galvanic) corrosion. Modern bronzes, cast in typical art foundries today, often show a high degree of inhomogeneity and various compositions due to many different casting methods in use and because of often very unrefined temperature control systems in processes of melting and solidification. In this work, we have studied several specimens of cast statuary bronzes and compared the results with the results obtained from the industrial standard bronze cast. In order to examine distribution of Sn as a major alloying element and Zn, Pb and Fe as trace elements larger area line scans were performed using PIXE (proton induced X-ray emission). Furthermore, the PIXE elemental maps allowed calculation of the homogeneity factor. The areas which have showed large scale inhomogeneities were subsequently examined by the means of PLP (potentiodynamic linear polarization) measurements, which were able to confirmed higher potential appearance of galvanic corrosion for those regions.

XRF; PIXE analysis

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