Properties of vitreous enamel coatings deposited on aluminium foam

Aluminum foams, realized by the production of air into metallic melt, show very interesting properties for a wide range of applications. This material with a very low density, due to the high degree of porosity of the structure, together with good mechanical properties, impact energy absorption and high temperature resistance, results one of the most promising new engineering materials. In several environments, in particular where there are present aggressive ions, as chlorides, or with a low pH value, the particular cellular structure reduces the corrosion behavior of this material. Some strategies are individuated to increase the corrosion resistance of the aluminum foam. The application of a vitreous enamel layer is a possible solution to obtain a good protection together with resistance at high temperatures. In this work the properties of porcelain enameled aluminum foam samples are evaluated. Starting from plate samples of aluminum foam produced by Alporas method, different enamel systems, made of 2 or 3 layers, are studied. A frit suitable for aluminum substrate without vanadium presence was used. Microstructure analysis was made to highlight the adhesion between enamel and metallic substrate, the filling of the open cell and the presence of defects in the glassy layers. The corrosion behavior of samples was evaluated by acidic salt spray test exposure following ASTM G58 standard. Mechanical properties with a 4 point flection measurement were obtained. Finally the behavior of the exposure to flame of enameled samples was tested in comparison to the uncoated foam.