Chemical, physical and morphological characterization of ZnNi films electrodeposited on 1010 steel substrate from acid baths containing polyalcohol

By de Oliveira, E.M. & Carlos, I.A.
Published in Surface and Coatings Technology NULL 2011

Abstract

ZnNi alloy electrodeposition on a 1010 steel electrode in boric-acid baths containing sorbitol, mannitol or glycerol was investigated by cyclic voltammetry. Electrodeposits obtained galvanostatically were characterized by SEM, EDS and XRD. It was found that in baths containing sorbitol or mannitol, the deposition current density (jd) was reduced, but in none of the baths was the initial deposition potential affected. SEM images of deposits revealed that the boric-sorbitol and boric-mannitol complexes refine the grain, even at high jd. XRD patterns of the ZnNi deposits produced at jd = 50 mA cm- 2, in ZnNi1 bath and in ZnNi1 bath contained sorbitol or mannitol, indicated that the films were formed mainly of Zn and γ1 phases. To ZnNi2 baths contained glycerol the films were formed of γ and γ1 phases. The Ni content in the deposits produced in the bath without polyalcohol or containing glycerol increased from ~ 5 to 19 wt.% with increasing jd. With sorbitol or mannitol, there was a smaller rise from ~ 7 to 10 wt.% Ni. Thus, ZnNi deposits providing sacrificial protection can be obtained in baths with or without polyalcohol. The linear polarization method showed that ZnNi alloy deposited from baths contained polyalcohol have greate Rp.

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