Eletrodeposição de ligas de Ni-W sobre aço carbono: caracterização dos filmes
Resumo
The electrodeposition of Ni-W alloy on steel
substrate from acid and alkaline solution containing NTA as a complexing agent for
Ni2+ and WO4
2-
ions was initially studied. EDX analyzes of the galvanostatically
produced films found that from the complex formed between Ni-NTA there was no
unloading of Ni2+ ions and, therefore, there was no alloy formation. Therefore, studies
of the Ni-W alloy were conducted in acidic and alkaline ion solutions in the presence
of aspartic acid, which complexes the Ni2+ ions, and also from the acid solution
containing the boric acid-sorbitol complex from which the Ni2+ remains free in solution.
The complexation of Ni2+ ions with aspartic acid shown in the species distribution
diagram was evidenced by the results obtained in the UV-Vis and in the potentiometric
titration. The voltammetric analyzes of the tested solutions observed that the increase
in the nickel concentration in the deposition bath, pH variation and variation in the
composition of the deposition bath did not influence the control of the reduction process
of the Ni-W alloy. SEM analysis of the Ni-W electrodeposits produced with qd = 40.00
C cm-2 showed that the films were smooth, cracked or had globular crystallites
depending on the composition of the bath and the deposition current density (jd)
studied. EDX analyzes of the Ni-W electrodeposits found that the W content varied
with the jd studied and with the composition of the deposition bath. The XRD analyzes
indicated, in general, that the solid solution of W in Ni was designed independently of
the deposition bath and the jd, and also through XRD analysis, the calculated grain size
showed that the W content presented in the films evolved in different grain sizes. The
testicles of adhesion of the films visited that, for the most part, the Ni-W films had good
adhesion to the steel substrate. Open circuit potential (Eca) studies as well as
polarization studies have found that Ni-W films protect steel from corrosion
Collections
Os arquivos de licença a seguir estão associados a este item: