SOUSA, M. B.; http://lattes.cnpq.br/8419050777743938; SOUSA, Mikarla Baía de.
Resumo:
The corrosion process is constantly transforming metallic materials so that their
durability and performance no longer satisfy their intended purpose. One way to
minimize corrosion in metallic materials is to coat them with other materials.
Electrodeposition is a method widely used to obtain metallic coatings resistant to
corrosion and mechanical wear. Through electrodeposition it is possible to obtain
metallic alloys, which are generally prepared in order to improve the properties of their
initial constituents. The proposed study aims to optimize the current density, bath
temperature and phosphorus concentration variables and obtain the Zn-Ni-Cu-P alloy,
characterizing it in terms of morphology, alloy composition, structure, microhardness
and corrosion resistance. For the optimization of the alloy electrodeposition process, a
23 full factorial design was used. The electrodeposition process of the alloy on a 1020
steel substrate was studied, using a bath containing copper sulfate, zinc sulfate, nickel
sulfate, sodium citrate, sodium hypophosphite and cyanide-free. A Zn-Ni-Cu-P coating
was obtained for the first time by the electrodeposition process. It was observed that the
increase in current density favored the increase of Ni, Cu and P and the decrease of the
Zn content. The increase in temperature caused an increase in the content of Ni, Cu and
P and a decrease in the content of Zn. The increase in sodium hypophosphite
concentration favored an increase in Zn, Ni and P and a decrease in Cu content. The
coatings were shiny and adherent to the steel substrate. The surface morphology of the
coatings showed amorphous behavior and the presence of nodules and cracks on the
surface. Regarding the corrosion tests, it was found that the nickel content in the
coatings obtained directly affected their corrosion resistance, since an increase in the
nickel content decreased the corrosion resistance of the coatings. The optimal values
found through linear potentiodynamic polarization were: cathodic current density of 55
mA/cm2, temperature of 50 oC and phosphorus concentration of 0.07 M; with these
parameters it was possible to reach a corrosion potential of -0.614 V, a polarization
resistance of 1.730λ KΩ and a corrosion current of 18.θ4η ȝA. The electrochemical
impedance tests confirmed the results obtained by the potentiodynamic polarization
tests.