Yearly Archives: 2014

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


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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.

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


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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.

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


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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 ᴼC – 50 ᴼC. 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).

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Coumarin Derivatives as Corrosion Inhibitors for Zinc in HCl Solutions


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(a) 4-hydroxy - coumarin

The inhibiting effect of some coumarin derivatives toward the corrosion of Zinc in 0.1M HCl solution was studied using weight loss and galvanostatic polarization techniques. Addition of KI to acidic medium containing the coumarin derivatives increases the inhibition efficiency of the system. The obtained results showed that the inhibition efficiency of these compounds increased by increasing their concentrations and decreased by rising the temperature, so that the adsorption of these compounds is physically adsorbed on the zinc surface. Temkin’s adsorption isotherm fits the experimental data for the studied compounds. Some thermodynamic parameters for the adsorption and activation process were computed. The values of Tafel slopes indicate that these compounds act as a mixed type inhibitors but cathode is more polarized when an external current was applied. The inhibitors are explained in terms of adsorption on the zinc surface. The order of inhibition efficiency are interpreted on the basis of the molecular structure, the subsistent groups and their charge densities of the coumarin derivatives.

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Phosphorus Determination of Electroless Nickel Depositions from Printed Circuit Boards (PCB) by means of EDXRF


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The principles of energy dispersive x-ray fluorescence (EDXRF) technique and its elemental analysis applications were described in some books and reviews [1-4]. PCBs are an important application for nickel-phosphorus (NiP) coatings, on top of which, additional gold and/or palladium coatings are applied. Phosphorous concentration of chemically (or electroless) deposited nickel-phosphorus (NiP) coating can be analyzed in nondestructive manner in atmosphere without stripping Au and Pd coatings. The FP-based WinFTM software allows a reliable determination of both the mass per unit area of the NiP layer and its P concentration [5]. The reproducibility and accuracy of the analysis is verified by means of certified standard reference material. Their quantification is traceable to accurate mass per unit area primary standards analyzed by several suitable techniques [6]. The typical measurement spot size is about 1mm, but in case of micro-spot instruments even smaller spot sizes (less than 100 µm) are achievable.

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