Electroless Ni–P and Ni–P–CuO coating on mild steel was developed successfully with the addition of Zwitterionic surfactant. The usage of nano-CuO in electroless coating was intermittent though the cost is low with high catalytic activity. Zwitterionic surfactant was introduced into the composite coating for the first time to increase the suspension of nanoparticles effectively during the coating process. Surfactant helps to reduce the intermolecular attraction between the solid and liquid interfaces and hence binding of nanoparticles with the hydrogen gas bubbles was eliminated. Also agglomeration of nanoparticles was controlled by stirring the electrolyte continuously using magnetic stirrer. The characterization and tribological properties were tested for the newly developed composites. Scanning electron microscope micrograph reveals the deposits are produced without any defects and the presence of CuO nanoparticles in the deposit. Energy-dispersive spectroscopy measurement shows the changes of weight percentage of elements available in the substrate. The surface roughness of the deposit was improved with the addition of CuO, it packs the gap between two grains and offers smooth finish and as the result the surface properties are modified. Microhardness of the substrate was improved for the substrate added with nano-CuO. The corrosion resistance of the substrate was improved when compared to the substrate produced using electroless Ni–P binary coating. Zwitterionic surfactant reduces the agglomeration of nanoparticles during chemical reaction and allows the particles to coat only on the target. Similarly, this technique can be implemented in the production of other composites in electroless coatings.

Estimation of Zwitterionic Surfactant Response in Electroless Composite Coating and Properties of Ni–P–CuO (Nano)Coating

Properties and applications of amphoteric surfactant: A concise review

Nickel-based multiwalled carbon nanotube (Ni–MWCNT) composite coatings were electrodeposited over the inner groove of an aluminim alloy rotor with Zn–Ni interlayer. The surface of the composite coating was investigated by X-ray diffraction and scanning electron microscopy. The hardness of the coating was determined by Vicker's method. It was revealed that Ni–MWCNT composite coating has uniformity in thickness over the surface of the aluminim groove and also better particle distribution over the area. It was found that there was a significant improvement in the microhardness values of Ni–MWCNT composite coating than uncoated aluminum alloy rotor. In addition, the wear resistance of the composite coated increased nine times than the uncoated substrate. Thus, Ni–MWCNT composite coated aluminum alloy rotor can enhance the performance and life-time of the rotor in the textile industries.

Nickel–multiwalled carbon nanotube composite coating on aluminum alloy rotor for textile industries

The present research uses the safer hydrogen halide to prepare the MgO-MgI2/MgBr2 layers onto AZ91 magnesium alloy in alkaline solution. The water-soluble metal salts (MgI2/MgBr2) were not responsible for the corrosion protection; whereas Mg(OH)2 formed first and then converted to MgO by heat-treatments and this MgO was responsible for the corrosion protection. The electrochemical results showed that the development of MgO mitigated the corrosion process and improved the corrosion resistance. This new treatment was then used as a pre-treatment for further electroless nickel (EN) deposition and it showed the good corrosion current density and better corrosion potential on the magnesium substrate. This new treatment and EN depositions were characterised by XPS and SEM. The electrochemical polarisation and EIS test of these EN depositions were evaluated in 3.5 wt.% NaCl. In addition, pitting behaviour of these EN depositions were evaluated by linear sweep voltammetry test.

Jiang Jing

Papers

A new method to prepare MgO and base for further electroless nickel deposition on magnesium substrate