Synthesis and characterization of hexafluorozirconic acid powder and its application in nanoceramic coating

Abstract

Abstract Most of the nanozirconia coating formulations are based on hexafluorozirconic acid solutions that may contain hexafluorosilicic acid indispensably. A new process has been developed to synthesize hexafluorozirconic acid in the powder form which is free from silica as indicated by the absence of Si peak in EDX spectrum. Nano-ceramic coating process is simplified by making up the bath solution using dry H 2 ZrF 6 powder and polyacrylic acid. The powder form makes transportation easier. Hexafluorozirconic acid powder based nano zirconia (PNZ) coat was characterized by FESEM (field emission scanning electron microscopy), EDX (Energy-Dispersive X-ray Spectroscopy), XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy) studies. The PNZ coat formed on mild steel (MS) was characterized by linear polarization (LP) studies and Electrochemical Impedance Spectroscopy (EIS) and also compared with the commercial nano-zirconia coating chemical (Bonderite NT-1) treated mild steel. Polyester epoxy powder coat (PEP) was applied on powder based nano zirconia treated mild steel (PEP/PNZ), and commercially Bonderite NT-1 treated mild steel (PEP/NT). The dry film properties of the organic coat with the nanoceramic base coat were studied by neutral salt spray test, humidity resistance, impact resistance and adhesion tape tests as per ASTM (American Society for Testing and Materials) methods. The corrosion resistance and adhesion of PEP/PNZ coating system are comparable with the performance of PEP coated on the commercial nano zirconia coating solution (NT-1).