Study on functionally graded Zn–Ni–Al₂O₃ coatings fabricated by pulse-electrodeposition

Abstract

Functionally graded Zn-Ni-Al 2 O 3 coatings were electroplated by continuously changing the duty cycle/frequency. Two types of graded coatings were deposited; the first type was synthesised through gradual reduction in the duty cycle from 88 to 11% at a certain frequency and the second type was plated by increasing the frequency gradually from 100 to 1500 Hz at a constant duty cycle. Microstructure and composition of coatings were determined by scanning electron microscope equipped with energy-dispersive spectroscopy. Corrosion behaviour was studied by potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS); and tribological properties were evaluated using the pin-ondisc test. The results showed in the first type, Ni and alumina contents, and microhardness were increased towards the surface. But in the second type, composition was less affected through frequency alterations. Increasing the frequency raised the corrosion rate in the range of 2.9-8.7 μA cm −2 and improved the wear resistance.

Electrodeposited Zinc-Nickel Nanocomposite Coatings

“…Shourgeshty et al examined multilayer coatings of ZnNi and ZnNi-Al 2 O 3 deposits. As expected, an increase in the number of layers improved the hardness values of the coatings but addition of Al 2 O 3 also had a positive effect[30,31].…”

“…Uptake of the nanoparticles is of interest as varying concentrations of nanoparticles are found, dependent upon the character of the particle being added to the solution. ZnNi coatings with Al 2 O 3 incorporation were found to contain anywhere from trace Al 2 O 3 up to 8.9 wt % throughout the literature [12,[27][28][29][30][31][32][33]. Zinc-nickel coatings with TiO 2 incorporation were found to contain on average 80-85% Zn, 12-17% Ni and 1.25-2.5% Ti [35][36][37].…”

“…A review of the literature shows most studies being performed under acidic conditions [32-37, 39-40, 44, 46] with little work in alkaline conditions [12,42,48]. ZnNi-Al 2 O 3 coatings were predominantly deposited under acidic conditions (pH = 4, 4.9 and 5.0) with one group examining deposition at pH = 13 [12,[27][28][29][30][31][32][33]. The literature for the deposition of ZnNi-TiO 2 coatings was done under acidic conditions with pH = 2.5, 4 and 4.6 from a variety of groups [11,[34][35][36][37].…”

Removal of Thiol-SAM on a Gold Surface for Re-Use of an Interdigitated Chain-Shaped Electrode

“…They have been applied for many applications in energy, biosensor, electronics, and semiconductor fields [ 1 , 2 , 3 ]. There are several deposition techniques, such as electrodeposition for the fabrication of Ni matrix micro- and nano-SiC composite coatings at room and elevated temperature [ 4 ], functionally graded Zn–Ni–Al 2 O 3 coatings [ 5 ], and nickel–fullerene C60 composition coatings [ 6 ]; vacuum thermal evaporation [ 1 , 2 ]; electron beam evaporation [ 7 ]; laser beam evaporation [ 8 ] for depositing thin films; electrochemical deposition for developing thin layers, graphene, and nanoparticles [ 3 , 9 ]; and chemical-absorption for depositing a self-assembled monolayer on a gold substrate [ 10 , 11 , 12 ].…”

Ceria Particles as Efficient Dopant in the Electrodeposition of Zn-Co-CeO2 Composite Coatings with Enhanced Corrosion Resistance: The Effect of Current Density and Particle Concentration

“…The MMC can be produced by different routes, such as powder metallurgy [ 13 ], metal spraying [ 14 ], physical vapor deposition (PVD), chemical vapor deposition (CVD) [ 15 ], or nitridation [ 16 ]. One of the main drawbacks of these techniques, among others, is working at high temperatures.…”