Comparative study on polyester epoxy powder coat and amide cured epoxy liquid paint over nano-zirconia treated mild steel

• Nanozirconia coating on mild steel.
• Evaluation of polyester epoxy powder coat on nanozirconia treated mild steel.
• Evaluation of amide cured epoxy paint on nanozirconia treated mild steel.
• Superior dry film characteristics of powder coating on nanozirconia treated mild steel.

The effect of commercial nano-sized zirconium hydrous oxide (NT) coating of mild steel (MS) on corrosion resistance and its adhesion to polyester epoxy powder coat (PEP) and amide cured epoxy white finish paint (EPF) was investigated. The corrosion rate of untreated and NT treated MS was evaluated from linear potential parameters such as corrosion current, corrosion potential and Tafel plots. NT base coat was characterized by EIS (electrochemical impedance spectroscopy), FESEM (field emission scanning electron microscopy), EDX (energy-dispersive X-ray spectroscopy), AFM (atomic force microscopy), XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy) studies. The dry film properties of the top coats of PEP and EPF were compared by neutral salt spray test, humidity resistance, impact resistance and adhesion tape tests as per ASTM (American Society for Testing and Materials) methods. The mechanism of zirconia deposition on the hydroxyl sites of the mild steel surface was evident from the results of XPS. The corrosion resistance and adhesion of PEP/NT coating system were found to be superior to that of EPF/NT system from salt spray resistance test and cross hatch test by adhesive tape. The superior corrosion resistance of EPF/NT to EPF/MS shows the efficacy of the NT conversion coating on MS.

Nano-zirconia coating on mild steel with the top coats of polyester epoxy powder and amide cured epoxy liquid paints exhibits superior performance. AFM image of nanozirconia coat on mild steel shows many clusters of globules due to Ostwald's ripening, the coating formed by hydrous zirconium oxide over the metal is in the order of nanometers.Figure optionsDownload as PowerPoint slide