A detailed study on the enhanced anti-corrosion properties of nano silicon dioxide additive influencing calcium modified zinc phosphate coating on mild steel

The influence of nano silicon dioxide additive on calcium modified zinc phosphated mild steel sample is researched in this paper. This study shows that the environment friendly nano additive provides a high porous, fine-grained and compact phosphate sealing by facilitating strong adsorption to the successive protective covering of mild steel. The formed coatings were characterised by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and atomic absorption spectroscopy (AAS). The thermal stabilities of the coatings were analysed by thermo gravimetric analysis (TGA). The coating quality on the mild steel surface was examined by coating weight, porosity and adhesion tests. The corrosion studies were done using salt spray test and electrochemical impedance spectroscopy. The good dispersibility of the additive was observed on the coating with increased safety from erosion. The lower i(corr) value of 2.6477 x 10(-5) A/cm(2) for CaZnPS when compared to 8.212 x 10(-5) A/cm(2) for CaZnP indicated that the nano additive has more shielding effect. The results reveal that the barrier and corrosion inhibition tendencies were increased with the addition of nano particles to the calcium modified zinc phosphated mild steel.