Synthesis and characterization of a novel non-chrome electrolytic surface treatment process to protect zinc coatings

A novel method for protecting zinc substrates using silicates has been explored as a promising alternative for the chrome passivation process. The silicate layer was deposited cathodically from a bath containing PQ solution and water. A post-treatment drying process was found to increase the Si content in the coating and improve the corrosion characteristics of the silicate layer. Deposition parameters such as concentration of the bath, applied voltage and deposition time have been optimized using corrosion characteristics and surface morphology. Stability of the coating has been improved by varying the drying temperature and the duration of drying. Finally, stability studies show that the silicate coatings obtained using this method exhibit a higher barrier resistance and better stability as compared to chrome passivates.