Highly Textured Zinc Thin Films through Novel Pulsed Electrodeposition Techniques and Their Applications

Abstract

The electrodeposition of zinc thin films has been widely investigated with extensive applications in corrosion, battery electrodes, photo- and electro-catalysis. Traditionally, the direct current (DC) method of electroplating has been explored in terms of varying current density to obtain changes in morphology, grain size, preferred crystalline orientation, which in turn have significant consequences for properties such as catalysis and corrosion resistance. We have recently demonstrated [1] a novel, additive-free pulsed plating method to control the specific crystalline growth orientations and average grain size of zinc electrodeposited on steel substrates.Specifically, we have observed a transition of the preferential (002) facets at low peak current density (or low duty cycle) to (101) preferring facets at higher peak current density (or high duty cycle) as determined by the analysis of texture coefficients. Further analysis using scanning electron microscopy reveals a transition from the conventional hexagonal-shaped particles of zinc to needle-shaped structures, accompanied by a change in average crystallite size from 33 to 19 nanometers, determined from X-ray diffraction studies. The variation in morphology is also correlated to crystallographic textures through the analysis of texture coefficients and an understanding of crystallization mechanisms occurring during deposition.Herein, we report on an application of these highly textured zinc-coated steel substrates towards corrosion resistance, through accelerated electrochemical testing. Using industry-standard ASTM methods such as Linear Polarization Resistance (LPR), Linear sweep voltammetry (LSV) and electro-impedance spectroscopy (EIS) measurements, we report on preliminary findings of corrosion potential, current and corrosion rates expressed in mm per year as a function of crystalline texture of the zinc thin films.