Characterisation of electrodeposited and heat-treated Ni−Mo−P coatings

• Autor(a) principal: Melo,Régis L.
• Data de Publicação: 2012
• Outros Autores: Casciano,Paulo N. S., Correia,Adriana N., Lima-Neto,Pedro de
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532012000200020
• topic: Ni−Mo−P; electrodeposition; amorphous; corrosion; hardness

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.