Chemicals used presently for corrosion inhibitors in Industries are highly toxic to both human beings and environment. These inhibitors may cause the damage to organ system viz., kidneys or liver, or to disturb a biochemical process of an enzyme system at some site in the body. For papaya seed, a vegetable waste is found to act as a very good green inhibitor, in preventing acid corrosion of low-carbon construction steel. The study was made in 0.5 to 3 N H 2 SO 4 with the variation of concentration. An increase in inhibitor concentration decreases the rate of degradation. But there is an optimum concentration at which the inhibitor effect is maximum, beyond that the corrosion rate again increases. The adsorption study shows that the mechanism of corrosion inhibitor is due to physical adsorption, following Temkin adsorption isotherms. Electrochemical impedance spectroscopy study showed that the corrosion inhibition by the papaya seed is due to an increase in polarization resistance and impedance at metalsolution interface.

In the present investigation, the friction stir welding of ultra low carbon steel was carried out at different tool rotational speeds of 300 to 900 rpm in steps of 150 rpm for 30 mm/min traverse speed. The macro and microstructures were examined to identify the different areas of stir zone, thermomechanically affected zone and heat affected zone of the welded joints. Tensile strength of the welded joints was evaluated and maximum tensile strength of ∼336 MPa was obtained at 450 rpm tool rotational speed. Microhardness was measured along the cross section of the welded joint. The maximum hardness was observed at stir zone when compared to thermomechanically affected zone and heat affected zone. The hardness values decreased with the increase in tool rotational speeds in the stir zone. Electrochemical study was investigated in 0.1 mol/L HCl solution using various electrochemical measurements such as open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization. The corrosion rate at stir zone decreased with the increase in tool rotational speed.

Ternary Ni-Co-P alloy coating was chosen to improve the corrosion resistance of the Copper substrate. Box-Behnken Design (BBD) of experiment was utilized for the optimization of the effects of different process parameters such as Cobalt Sulphate, Sodium Hypophosphite, and temperature. Electrochemical Impedance Spectroscopy (EIS) was used to study the corrosion resistance behaviour of different samples by altering different parameters. Analysis of Variance (ANOVA) was done to determine the important process parameters and their significant interactions. The surface morphology, microstructures and elemental compositions of the as-deposited coatings were analyzed using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDX) respectively. Finally, 15g/L of Cobalt Sulphate, 25g/L of Sodium Hypophosphite, and 85°C of bath temperature were found out to be the optimum conditions for coating deposition in order obtain a corrosion resistance of 1165 ohm-cm2.

This study focuses on the electroless deposition of Ni–P alloy over a copper substrate to minimize the corrosion rate of the substrate. Central Composite Design (CCD) has been performed using Design-Expert software for minimizing the corrosion rate of the coating. Along with that, CCD is also utilized to analyze the influence of various process parameters viz. concentration of Nickel Sulphate, the concentration of Sodium Hypophosphite and bath temperature. Potentiodynamic test has been employed to evaluate the corrosion rate of each of the coated substrates. In order to minimize the corrosion rate, optimization has been performed using particle swarm optimization (PSO). 21.59[Formula: see text]g/L of Nickel Sulphate, 26. 72[Formula: see text]g/L of Sodium Hypophosphite and 93.41°C as the bath temperature were the optimum conditions for the deposition of coating in order to achieve a corrosion rate value of 0.862[Formula: see text]mm/Yas obtained from the model analysis results. Further, Analysis of Variance (ANOVA) was implemented which corroborated that the parameter Nickel Sulphate along with the interaction between Sodium Hypophosphite and bath temperature were the significant ones in determining the corrosion rate of the coating deposited in optimized condition. Optical Microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray analysis (EDX) were conducted to study the surface morphology and the elemental composition of the coated substrate respectively.

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