Morphological Aspects and Corrosion Behaviour of Phenol Formaldehyde/Zn Composite Coatings

Abstract

The present work has the purpose of studying morphological aspects and corrosion behaviour of pure zinc and composite coatings having zinc as metal matrix and phenol – formaldehyde resin type Novolac (RESITAL 6358/1) as dispersed phase obtained during the electrodeposition process of zinc. The phenol – formaldehyde resin/Zn composite coatings were electrodeposited from a suspension of phenol – formaldehyde resin particles in aqueous zinc sulphate electrolyte by adding 10g/L and 25g/L of phenol – formaldehyde resin particles in the electrolyte solution. The dimensions of resin particles were 0.1 - 5μm. The morphological aspects of the coatings were investigated by scanning electron microscopy method. While the pure zinc coatings have a rather regular surface, the composite coatings surfaces have finer grains and different morphologies. The electrochemical behaviour of the coatings in the corrosive solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy methods. As electrochemical test solution, 0.5M NaCl was used in a three electrode open cell. The polarization resistances of phenol – formaldehyde resin/Zn composite coatings are bigger than that of pure zinc coatings obtained under the same condition for electrodeposition.