Formation of aluminum phosphate coating on graphite by cathodic electrochemical treatment

Electrochemical treatment is a new method for accelerating the phosphating processes at low temperatures that can be performed as cathodic and anodic treatments. In this study, aluminum phosphate coating was deposited on graphite by cathodic electrochemical treatment, and, then heat treatment was performed on it. Microstructure, chemical composition, phase structure and adhesion of the coating produced in current densities of 35, 45, and, 55 mA/cm2, temperatures of 55, 70, and, 85 °C, and, treatment types of a three-layer coating at 120 min and a single-layer coating at 360 min were characterized using a scanning electron microscope, energy dispersive X-ray analysis, X-ray diffraction, and, scribe-grid test. The results revealed that the three-layer aluminum electrophosphate coating deposited in the current density of 35 mA/cm2, temperature of 70 °C, and, treatment time of 120 min was favorable due to a dense microstructure, suitable thickness, and, good adhesion. Furthermore, the phase that was formed in this coating was characterized as Al(PO3)3.