Development of a Novel Electrochemical Method to Deposit High Corrosion Resistant Silicate Layers on Metal Substrates

A novel method for electrodepositing silicates on metallic substrates from aqueous solutions has been developed. The technique is demonstrated by forming a passive film on galvanized steel. The silicate layer was deposited cathodically from a bath containing PQ Corporation N sodium silicate solution ~3.22 weight ratio sodium silicate, 37.5% solution in water!. A post-treatment drying process increased the Si content in the coating and improved the corrosion characteristics of the silicate layer. Deposition parameters like bath concentration and temperature have been optimized using corrosion characteristics and surface morphology of the final coating. Finally, stability studies show that the silicate coatings obtained using this method have higher barrier resistance and better stability as compared to chrome passivates. The technique developed here shows promise as an alternative to chrome passivation for corrosion protection of metals.