Chemically-bonded phosphate ceramics obtained from aluminum anodizing waste for use as coatings

Aluminum anodizing waste (AAW) was used to obtain coatings based on chemically-bonded phosphate ceramics (CBPCs) to replace primary sources of aluminum compounds. The AAW was washed to obtain aluminum hydroxide, which was used to prepare the monoaluminum phosphate (MAP) binder and calcined to obtain alumina. The coatings were applied onto ceramic substrates by spraying and cured at 350 °C for 20 h. After curing the coatings were characterized by SEM, XRD and the pin-on-disk abrasive wear test. The results obtained with the use of AAW in the form of MAP were equivalent to those obtained using a primary source of aluminum hydroxide. AAW calcined at 1300 °C presented transition alumina phases and a surface area of around 8.25 m2 g−1. The coating showed low wear resistance and microfissures. The AAW calcined at 1500 °C provided wear resistance results equivalent to samples produced with commercial alumina. Only alpha alumina was identified. The surface area of around 1.54 m2 g−1 was also similar to that observed for commercial alumina (1.1 m2 g−1). The results indicate that AAW can be used as a raw material for the production of CBPCs, representing an alternative for adding value to an industrial waste.