Resumo

MELO, Régis L.; CASCIANO, Paulo N. S.; CORREIA, Adriana N.  e  LIMA-NETO, Pedro de. Characterisation of electrodeposited and heat-treated Ni−Mo−P coatings. J. Braz. Chem. Soc. [online]. 2012, vol.23, n.2, pp. 328-334. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532012000200020.

The electrodeposition, hardness and corrosion resistance properties of Ni−Mo−P coatings were investigated. Characterisations of the electrodeposited coatings were carried out using scanning electron microscopy, X-ray diffraction and energy dispersive X-ray analysis techniques. Corrosion tests were performed at room temperature in 10^-1 mol dm^-3 NaCl solutions and by potentiodynamic linear polarisation. Amorphous Ni−Mo−P coatings were successfully obtained by electrodeposition using direct current. The coating composition showed to be dependent on the bath composition, current density and bath temperature. Both P and Mo contents contribute for the hardness properties of the Ni−Mo−P coatings and the absence of cracks is a requirement to produce electrodeposited Ni−Mo−P coatings with good hardness properties. The hardness values increase with heat-treatment temperature due to the precipitation of Ni, Ni₃P and NiMo phases during the heat treatment. The corrosion resistance of the electrodeposited Ni−Mo−P amorphous coatings increases with P content in the layer. Among the electrodeposited Ni−Mo−P amorphous coatings, Ni₇₈Mo₁₀P₁₂ presented the best hardness and corrosion-resistance properties. The results showed that the addition of P is beneficial for the hardness and corrosion resistance properties of the Ni−Mo-based coatings.

Palavras-chave : Ni−Mo−P; electrodeposition; amorphous; corrosion; hardness.