Nano Silicon Dioxide Accelerated Zinc Phosphate Conversion Coating on Mild Steel Using Decyltriethylammonium Bromide as an Additive

摘要

In this work, the phosphating process was accelerated by ECO-friendly nano silicon dioxide along with decyltriethylammonium bromide as an additive. Accelerator and additive incorporation effectively reduced the extent of zinc dissolution during phosphating and activated the process to achieve the coating weight faster. Also it yielded coatings with greater thickness than the normal phosphate coating. The parameters such as coating weight, surface coverage, roughness and corrosion resistance due to the presence of nano silicon dioxide and decyltriethylammonium bromide were evaluated. X-ray diffraction (XRD), Atomic force microscope (AFM) and Scanning electron microscopy (SEM) were availed to study the chemical composition, modified surface and microstructure of the phosphate coatings. XRD studies revealed the presence of Zn-3(PO4)(2)center dot 4H(2)O (hopeite) and Zn2Fe(PO4)(2)center dot 4H(2)O (phosphophyllite) in the composition of the phosphate coating. The corrosion behaviour of the coated steel was assessed by open circuit potential, potentiodynamic polarization curve and electrochemical impedance spectroscopy.