INQUINOA   21218
INSTITUTO DE QUIMICA DEL NOROESTE
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Functionalization of nanostructured Ni-W coatings obtained by electrodeposition
Autor/es:
M.P. QUIROGA ARGAÑARAZ, S.B. RIBOTTA, G. BENÍTEZ, A. RUBERT, L.M. GASSA, R.C. SALVAREZZA, M.E. VELA, J.M. RAMALLO-LÓPEZ.
Lugar:
Lausanne
Reunión:
Congreso; 65th Annual Meeting of the International Society of Electrochemistry.; 2014
Institución organizadora:
International Society of Electrochemistry
Resumen:
Ni?W nanostructured coatings electrodeposited on carbon steel by galvanostatic pulse programs have valuable properties for technological applications. They exhibit high hardness (800-900 Hv), absence of brittleness and better corrosion resistance than that of the underlying steel. The surface of the coating consists of 10-50 nm crystals forming a cauliflower-like structure protected by a mixture of nickel and tungsten oxides as was demonstrated by AFM and XPS techniques. The cauliflower structure is preserved into the bulk coating which exhibits an average composition 70 at% Ni-30 at% W as was determined by SEM and TEM.
The possibility to further improve the corrosion resistance was explored by functionalization of the Ni-W coatings with silanes.
Ni-W substrates were ultrasonicated in acetone during 10 minutes. The samples were dipped in the solution containing approximately 20 ml of 2 mM tetraethoxysilane (TEOS) solution in toluene. The SAM solution was maintained at 80ºC for 3 h in a hot water bath. After the immersion, the samples were immediately dipped in a second solution containing 20 ml of 7 mM octadecyltrichlorosilane (OTS) in hexane for 24 h. Finally the substrates were rinsed in hexane to remove loosely bound materials and subsequently air dried. AFM images show that the silanization does not alter the surface morphology. XPS results for the first layer of silanes (TEOS) indicate a Si/Ni ratio of 0.8 and after the OTS treatment this value is greater than 1 indicating the presence of multilayers or a polymerized silane film. The contact angle of bare Ni-W is 53° and after the silanization increases up to 106°. The electrochemical response of silanized Ni-W coatings opens the possibility to a new design to improve the corrosion resistance of the electrodeposited films.