Electrodeposition and electrocatalytic performance of Ni-Co alloy

Fig. 1: Customized tubular three electrode cell with provision to collect liberated O2/H2 on electrode surface

The electrodeposition of Ni-Co alloy coatings on pure copper has been carried out at different current densities (c.d.) from an aqueous sulphate bath at room temperature. The effects of c.d. on deposit characters such as composition, hardness and thickness have been studied. The electrodeposited Ni-Co coatings were tested for their electro-catalytic behaviors, namely for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 6M KOH by cyclic voltammetry and chrono-potentiometry techniques. The surface morphology and phase structure of the deposit corresponding to different c.d.s were studied using, respectively FEGSEM and XRD study. The chrono-potentiometry study revealed that Ni-Co alloy coating deposited at 4.0 Adm-2 is more electro active for HER and that deposited at 1.0 Adm-2 is more electro-active for OER. Hence, Ni-Co alloy coatings deposited at 4.0 Adm-2 and 1.0 Adm-2 can be used as efficient electrode materials for, respectively HER and OER reactions finds applications in fuel cells as demonstrated by cyclic voltammetry (CV) and chrono-potentiometry experiments. The characteristic electro catalytic behaviour of the coatings for HER and OER are attributed to the inherent phase structure, composition, specific surface area and porosity of the coated materials under test, determined by the cathode current density at which they are deposited, supported by FEGSEM and XRD study.


    

The 11th China (Guangzhou) International Surface Finishing, Electroplating and Coating Exhibition

The 11th China (Guangzhou) International Surface Finishing, Electroplating and Coating Exhibition, SF Expo China 2015 for short, will be held from 11-13, May 2015 in Poly World Trade Center, Guangzhou, China. As the most professional and rapidly developing surface finishing exhibition, SF China Expo has become an important surface industry event in China and the first UFI approved surface expo in the world. SF China Expo 2013 has attracted over 200 leading surface suppliers from all over the world such as MacDermid, COVENTYA, Toyotsu Chemiplas, FISCHER, Atotech, SurTec, Uyemuba, Wagner, Nordson, Chemetall, Norilsk etc. We are looking forward to your participation.


    

Non ionic surfactants derived from phenol compounds as inhibitors for corrosion of aluminum in hydrochloric acid solution

The chemical structure of three non ionic surfactants derived from phenol compounds

Inhibition of aluminum corrosion in 1M HCl in absence and presence of three compounds of non ionic surfactants compounds derived from phenol was investigated using hydrogen evolution reaction, weight loss galvanostatic polarization and electrochemical impedance spectroscopy techniques. It was found that the percentage inhibition increases with increasing the concentration of inhibitor, amount of ethylene oxide unit and with decreasing temperature. The inhibitive action of non ionic surfactant compounds was explained in terms of blocking the electrode surface by adsorption process. The adsorption process follows Langmuir isotherm. The polarization measurements showed that these inhibitors are acting as mixed inhibitors for both cathodic and anodic reaction. Electrochemical impedance spectroscopy technique exhibit one capacitive loop indicating that, the corrosion reaction is controlled by charge transfer process. Some activated thermodynamic parameters are calculated and explained.


    

Effect of additives and operating parameters on deposit characters of Ni-Cd alloy

Figure 3

The Ni-Cd alloy coating was electrodeposited on mild steel (MS) from acid chloride bath using gelatin and glycerol as additives, individually and in combination. The bath composition and operating parameters have been optimized by conventional Hull cell method. The effect of current density (c.d.) on Ni content of the alloy was studied at different molar ratio of metal ions in the bath. The effects of c.d. and temperature on thickness, hardness, and composition and corrosion rate (CR) of the coatings were studied. Cyclic voltammetry (CV) study showed that (gelatin + glycerol) has significant effect on process of deposition and (gelatin + glycerol) worked synergistically to increase the Ni content by their preferential deposition and by suppressing the deposition of more readily depositable Cd2+ ions. Ni-Cd bath having both [Ni2+]/[Cd2+] = 1.5 and 8.0 exhibited anomalous type of codeposition at all c.d.’s studied. Corrosion behavior of the coatings evaluated by electrochemical methods demonstrated that the coating from bath [Ni2+]/[Cd2+] = 15, deposited at 4.0 A dm-2  is the most corrosion resistant. The superior corrosion resistance of Ni-Cd coatings at optimal c.d. was attributed to specific Ni (111), Ni (200), Cd (200) and Ni-Cd (862) reflections, evidenced by XRD study. The surface morphology was analyzed using SEM study, and results are discussed.


    

Electrochemical Investigation on the Corrosion Behaviour of Mg-Al-Zn-Mn (GA9) Alloy in Sodium Chloride Medium

Fig. 2: Nyquist plots for the corrosion of GA9 magnesium alloy in different concentrations of NaCl solutions at 40°C

The corrosion behavior of Mg-Al-Zn-Mn (GA9) alloy in sodium chloride solutions was studied over a range of concentrations and solution temperatures by electrochemical techniques like potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). The studies were carried out in solutions with NaCl of concentrations between 0.1M – 2M; and at different temperatures in the range of 30 C – 50 C. The studies have revealed that the corrosion rate of GA9 magnesium alloy increases with the increase in temperature and also with the increase of NaCl concentration in the medium. Activation parameters like activation energy, enthalpy of activation and entropy of activation for evaluation of the corrosion process were calculated. The results from both the techniques are in good agreement with each other. The alloy surface morphology was studied before and after corrosion using scanning electron microscopy (SEM).