Surface protection of copper by allyl thiourea and hybrid sol-gel coatings

A novel approach has been adopted in the surface protection of copper by combining allylthiourea (ATU) and two silanes viz., 3-glycidoxypropyitrimethoxysilane (GPTMS) and tetraethoxysilane (TEOS) forming the hybrid sol-gel coating which is designated as Hy. At first ATU was immobilized on the copper surface to introduce active tail amino groups. Subsequently, Hy sol-gel was grafted onto the ATU modified copper surface. The interaction of ATU with copper and Hy monolayers were investigated by Fourier transform infrared spectroscopy (FT-IR) which revealed the chemisorption of ATU through Cu-S bonds. Besides, it also exposed the cleavage of epoxy ring due to the reaction with free amino groups of ATU. The surface protection of these monolayers were examined by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization studies (PDS) and cyclic voltammetric (CV) techniques, while the surface morphology was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. These results indicated that combination of ATU and Hy sol-gel coatings over copper displayed excellent surface protection. (C) 2015 Elsevier B.V. All rights reserved.