Awanikumar P. Patil

Evaluation of Microstructure, Mechanical Properties and Corrosion Resistance of Friction Stir-Welded Aluminum and Magnesium Dissimilar Alloys

Microstructure, mechanical properties and corrosion resistance of dissimilar friction stir-welded aluminum and magnesium alloys were investigated by applying three different rotational speeds at two different travel speeds. Sound joints were obtained in all the conditions. The microstructure was examined by an optical and scanning electron microscope, whereas localized chemical information was studied by energy-dispersive spectroscopy. Stir zone microstructure showed mixed bands of Al and Mg with coarse and fine equiaxed grains. Grain size of stir zone reduced compared to base metals, indicated by dynamic recrystallization. More Al patches were observed in the stir zone as rotational speed increased. X-ray diffraction showed the presence of intermetallics in the stir zone. Higher tensile strength and hardness were obtained at a high rotational speed corresponding to low travel speed. Tensile fractured surface indicated brittle nature of joints. Dissimilar friction stir weld joints showed different behaviors in different corrosive environments, and better corrosion resistance was observed at a high rotational speed corresponding to low travel speed (FW3) in a sulfuric and chloride environments. Increasing travel speed did not significantly affect on microstructure, mechanical properties and corrosion resistance as much as the rotational speed.

Effect of Welding Processes on Microstructure, Mechanical Properties, and Corrosion Behavior of Low-Nickel Austenitic Stainless Steels

Abstract In the present study, the influence of welding process on metallurgical, mechanical, and corrosion behavior of shielded metal arc welding and tungsten inert gas welding was explored using 308L electrode. Tungsten inert gas welding exhibited equiaxed grains, having better hardness and tensile strength than that of its counterpart. It is observed that heat-affected zone and unmixed zone of shielded metal arc welding is wider than tungsten inert gas welding. Dendrite length and inter-dendritic distance are smaller for tungsten inert gas welding. The volume fraction of ferrite is found to be higher in tungsten inert gas welding. The base metal shows higher ductility than both the weld; also, the ductility of tungsten inert gas welding was marginally better than shielded metal arc welding. Modified Strauss test shows intense grain dropping and strength reduction in both the process. The pitting corrosion resistance is found to be better for tungsten inert gas welding as compared to shielded metal arc welding. The galvanic current shows higher current density when couples are formed with base metal and weld zone produced by tungsten inert gas welding.

Passive direct alcohol fuel cell using methanol and 2-propanol mixture as a fuel

This article examines the effect of addition of small concentration of 2-propanol on the direct methanol fuel cell (DMFC) in passive mode. The different concentration ratio of the alcohol mixture (methanol +2-propanol) is used with constant methanol concentration and by varying 2-propanol concentration in the solution. The new passive direct alcohol fuel cell (DAFC) performance with different alcohol concentration ratio (ACR) has been compared with conventional passive DMFC. The cyclic voltammetry (CV) test, polarization test, and electrochemical impedance spectroscopy (EIS) are carried out to complete the different aspect of the cell performance. The result shows that DAFC with different ACR yields the better performance than the conventional passive DMFC. In this study, the passive DAFC at 1:0.5 ACR shows the optimum cell performance.

Effect of various ratios of nitric acid – chloride on electronic properties of passive films on AISI 304L stainless steel

Abstract In this study, the electrochemical behavior of 304L SS stainless steel in various nitric acid/chloride ratios was investigated. The characteristics of the passive film, formed at the open circuit potential (OCP) and at the passive potential (0.65 V vs SCE) were also compared. OCP results show that a stable passive film formed over the surface with higher nitric acid/chloride ratios. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements showed that with higher nitric acid/chloride ratios, the film resistance increases (R1) for OCP, passive potential, and the critical current density (icrit) and corrosion rate (icorr) decreases. Mott–Schottky analysis revealed that the film formed at OCP shows n-type behavior for 0.01 N and 1 N concentration and shows p-type behavior for 0.1 N nitric acid concentration. At 0.65 V (vs. SCE) of film formation potential, the film formed in 1 N concentration shows n – type behavior. In 0.01 N and 0.1 N acid concentration, p-type behavior has been observed. Also, according to Mott–Schottky analysis, it was found that a lower defect density was found in 0.1 N nitric acid, for both the potentials. X-ray photoelectron spectroscopy spectra show evidence that the surface contains Fe and Cr as major elements. However, at OCP, Fe2O3 was the main constituent of the passive film, whereas the passive potential film was rich in Cr2O3. In addition, nitrogen and chloride were adsorbed in the passive film at passive potential.

Effect of Zn addition on corrosion resistance of Cu-10Ni alloy in clean and sulphide contaminated seawater

ABSTRACT Cu-10Ni alloy has an outstanding resistance to corrosion in seawater due to formation of protective Cu2O film. However, in presence of S2− ions, it suffers accelerated corrosion. The present paper investigates the corrosion behaviour of Cu-10Ni, Cu-10Ni-6Zn and Cu-10Ni-12Zn alloys using weight loss, electrochemical impedance spectroscopy and potentiodynamic polarisation technique. The experiments were performed in clean seawater and sulphide contaminated seawater. The Cu-10Ni-6Zn and Cu-10Ni-12Zn alloys were found to exhibit lower corrosion rate than Cu-10Ni alloy in clean and sulphide contaminated seawater. Lower corrosion rate of Zn containing alloys in clean seawater is attributed to the incorporation of Zn2+ ions in Cu2O lattice. Lower corrosion rate of Zn containing alloys sulphide contaminated seawater is attributed to formation of ZnS in the film.

Corrosion Resistance of a New Cu-Alloy (Low Ni) vis-à-vis Cu-10Ni Alloy in Sulfide Polluted Synthetic Seawater

Cu-10Ni alloy suffers accelerated corrosion in sulfide polluted seawater. As an alternative, a new single phased, Cu-28%Zn-5%Ni-5%Mn-2%Fe alloy (hereby referred as CNZ-alloy) is developed and tested for the corrosion resistance in clean and sulfide polluted synthetic seawater. The CNZ-alloy showed better corrosion resistance than the standard Cu-10Ni alloy in both the test solutions i.e. clean and sulfide polluted synthetic seawater with . The results are discussed on the basis of polarization and electrochemical impedance spectroscopy. The better corrosion resistance of CNZ-alloy is attributed to the formation of protective ZnS and MnS2 films.