جستجوی مقالات مرتبط با کلیدواژه "electrochemical corrosion" در نشریات گروه "مواد و متالورژی"

this research focused on investigating the optimization and corrosion studies of rhodium plating coatings. Firstly, a rhodium coating was applied to the Inconel 600 super alloy substrate for 2, 5, 10, 20 and 50 minutes, using the electroplating process of sulfate solution. Using scanning electron microscope (SEM) and X-ray energy spectroscopy (EDS) images, the thickness, morphology and elemental analysis of the surface coatings were investigated and effect of rhodium plating time on the thickness and surface roughness of the coating was investigated. Finally, the corrosion resistance of rhodium coatings in 3.5%wt NaCl solution was evaluated using electrochemical tests: open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and tafel polarization, respectively. The results of SEM and roughness measurement studies in comparison results of rhodium coating showed that the electroplated rhodium coating had the highest resistance to electrochemical corrosion in 10 minutes, the thickness of the coating was 1.27μm and the corrosion current was 6.25nA/cm2 and the corrosion potential was determined to be 193mV vs SCE. the changes in the surface roughness were similar to the results of fitting the simulated electrical equivalent circuit for the double layer capacitance of the electrochemical impedance test.

In this study, the effect of strainin thermomechanical two-step aging heat treatment on mechanical properties and electrochemical corrosion resistance of Al-2024 alloy has been investigated. These results were compared with normal aging T6. For this research, samples of Al-2024 alloys were placed at ambient temperature during normal aging under different percentages of strain, and then aging treatment was completed. Four strains of 10%, 30%, 50% and 65% were applied on the samples by rolling machine. The results of tensile test with low strain rate, potentiodynamic polarization curves and optical microscopy indicated that the sample with 50% strain offered optimum combination of microstructure, mechanical strength and corrosion resistance. This is due to the fine and uniform distribution of precipitates that cause increasing of yield strength, tensile strength and corrosion resistance by 27%, 10%, and 83%, respectively, in comparison with T6 heat treated[MP2D1] . Therefore applying strain of 50%, can increase the corrosion resistance with maintaining high strength in two-step aging and thermomechanical heat treatments.

In this study we investigated the effect of potassium hydroxide and sodium silicate concentration into micro arc oxidation electrolyte on the corrosion behavior and micro-structure of the ceramic coating formed on the 6061 Al alloy. The potentio-dynamic polarization was applied to investigation of corrosion behavior of micro arc oxidation coating in 3.5 wt.% NaCl. XRD analysis, SEM and EDX were used for studying and identification of coating morphology, micro-structure and chemical analysis, respectively. The potentio-dynamic polarization results showed that the corrosion behavior was improved by increasing of potassium hydroxide and sodium silicate concentration into coating electrolyte. The XRD pattern showed that oxide ceramics and inter metallic compounds have formed on the surface under micro arc oxidation process. SEM and EDX illustrated the increase in the concentration of potassium hydroxide and sodium silicate lead to a reduction in breakdown voltage which in turn improves the surface quality as decreased in micro-cracks and features.

In this study, the surface of the samples were hardened by pulsed Nd:YAG laser. After determination of optimal parameters of laser transformation hardening of mentioned steel and improving in hardness compared to previous studies by pulsed Nd:YAG laser, the pitting corrosion behavior of hardened and as received surfaces were compared. SEM and Optical microscopic studies were done to study the microstructure. Cyclic polarization tests were used to study the electrochemical corrosion behavior. The result showed that in the result of solid- state transformation and refining of carbides in the steel matrix, improvement in the depth and surface hardness was obtained and the hardness of about 700 Vickers in the surface was gained. The polarization curves showed increased 113mV in potential. It was observed that this steel didn’t have repassivation capability even after laser surface hardening.

In the present study، NiCr coating was created by the High Velocity Oxy-Fuel (HVOF) thermal spray technique under different conditions in respect to powder feed rate and fuel/oxygen ratio on the steel samples. Electro chemical corrosion behaviour of the NiCr coated samples was investigated by the potentiostatic polarization in NaCl 3. 5% solution. In order to determine the structural traits of the coatings، scanning electron microscopy (SEM/EDX) was used before and after the corrosion testing. The analysis of the results indicates that the fuel/oxygen and the powder feed rate have a significant effect on the porosity،existing oxide phases، and corrosion resistance، and un/melted powders of these coatings. corrosion behaviour of the sample، which has coated by fuel/oxygen of 1. 25 and powder feed rate of 18 gr/min، is the best due to lower porosity and oxide zones.

Electrochemical and corrosion behavior of Ti-Al stable intermetallics (TiAl, Ti3Al and TiAl3) in H2O2 solution at different concentrations with constant pH of 12.5 was studied in this paper. As-casted alloys were fabricated under vacuum arc remelting (VAR) process. Then the samples were examined in H2O2 solution using different electrochemical analysis containing potential-time, potentiodynamic polarization and electrochemical impedance. The results showed that the concentration of the electrolyte had a considerable effect on the corrosion of the specimens. At higher concentrations an inductive element was also observed in the EIS curves. Anodic polarization behavior of titanium aluminide specimens in H2O2 was relatively similar, all showing passivity. However, the passive current density increased by increasing Al content in the intermetallic.