Authors: José Luis OrtizAparicio Yunny Meas Gabriel Trejo Raúl Ortega Thomas W Chapman Eric Chainet
Publish Date: 2012/12/19
Volume: 43, Issue: 3, Pages: 289-300
Abstract
This work reports the effects of four organic compounds referred to as levelers on the electrodeposition of Zn on steel from alkaline freecyanide electrolytes The additives tested included polyvinylalcohol PVA and the condensation products of epichlorhydrin with amines called polyamines PAs that were synthesized using an aliphatic amine PAI from diethylamine and PAII from diethylaminetriethylamine and a heterocyclic quaternary imidazolium molecule PAImid from imidazole These compounds were evaluated in the absence and in addition to a quaternary ammonium brightener Nbenzyl3carboxylpyridinium chloride 3NCP The imidazole derivativebased polyamine PAImid causes greater inhibition of the zinc reduction process than the aliphatic polyamine and more cathodic overpotential is necessary to promote massive metal deposition The morphology of the deposits is modified when polyamines are added to the bath more compact and smaller crystals are obtained with PVA as well as with polyamine PAI The addition of PAII as well as PAImid yields crystals growing perpendicular to the substrate The addition of 3NCP with PVA PA or PAImid increased the deposition overpotential and modified the morphology by diminishing the grain size In the absence of additives crystallographic orientation favored the basal Zn002 with high atomic packing The addition of the levelers favored the highangle pyramidal Zn101 with low atomic packing The combination of the levelers with 3NCP favored the prismatic Zn100 crystallographic orientation Additives decrease the size of zinc crystals and tend to increase the energy of lattice favoring the growth of pyramidal and prismatic planes
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