Zinc-nickel alloy coatings are electrodeposited on carbon steel from chloride bath using a technique of chronopotentiometry at different temperatures. The elemental composition and surface morphology analysis of zinc-nickel coated samples are done using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The coated samples are immersed in 3.5 wt.% sodium chloride solution and measurements of corrosion rate are done using linear polarization resistance. Scanning electron microscopy results show that deposition temperature variation has a strong effect which changes the surface morphology and elemental composition of zinc-nickel alloy coatings. The nickel content in the electrodeposited zinc-nickel alloy coatings increases with increasing deposition temperature. Uniformity and compactness of the coatings decrease with an increasing temperature. Cracks intensity increases with increasing deposition temperature which is attributed to internal stress due to factors that might be related to hydrogen evolution reaction. The linear polarization resistance results correlated with the morphology and compositional properties of zinc-nickel alloy coatings deposited at different temperatures, that with an increase deposition temperature, corrosion resistance decreases. Zinc-nickel alloy coatings with high corrosion resistance, compact and uniform morphology with less crack, and nickel content within the range of 12 wt.% to 15 wt.% are achieved with deposited coating at 25 8C.
This paper describes the study of electrodeposition process by cyclic voltammetry for Zn-Ni bimetallic coating on the X52 carbon steel substrate. Prior to the deposition at the bath temperatures of 25°C, 40°C, and 60°C, investigations were carried out to find the optimum potential range for zinc-nickel coatings with respect to the Ag/AgCl reference electrode. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) was used for surface morphology and elemental composition studies. The corrosion rate of the deposits was studied using the linear polarization resistance (LPR) method by immersing the samples (with and without coating) into 3.5% NaCl solution for 24 h. SEM and EDX results showed that the bath temperature has affected the formation of the microstructures and composition of coating. In addition, micro-cracks, nickel content, mobility of ions and compactness of microstructure increased by raising the bath temperature used for electrodeposition. The corrosion rate obtained from the LPR method can be correlated with the SEM/EDX analysis. The coating deposited at the temperature of 60°C including more content of nickel and micro-cracks led to lower corrosion resistance compared to the coating deposited at the bath solution temperatures of 25°C, 40°C, and non-coated X52 steel. Based on the results, the Zn-Ni coating deposited on the X52 steel substrate in the bath solution at 40°C presented the best performance due to more suitable achievements of microstructure compaction, composition, microcracks, and corrosion resistance observations.
Electrochemical CO2 reduction reaction (CO2RR) has been studied in 0.1 M of KCl (pH of 6.96), NaHCO3 (pH of 8.3) and K2CO3 (pH of 11.36) cathodic solutions with various counter electrodes including graphite rod, SS316 rod and Pt mesh at different potential ranges on the Znx-Ni1-x bimetallic electrocatalysts. Among the Znx-Ni1-x electrocatalysts, the Zn-Ni electrode with a composition of 65 wt% Zn and 35 wt% Ni and cluster-like microstructure has the best performance for CO2RR by according to minimum coke formation and optimum CO and H2 faradaic efficiencies (CO FE%=55% and H2 FE% =45%). The cyclic voltammetry (CV) measurements and gas chromatography (GC) analysis for the CO2RR showed that KCl solution as the cathodic electrolyte with pH of 7 has the best performance and appropriate faradaic efficiency for H2(40%) and CO(30%) products in low potential value (-0.6 v) in this study. The best potential range for the CO2RR on the Zn-Ni bimetallic electrocatalyst in KCl solution with the scan rate (SR) 0.05 V. s-1 is between -0.3 V to -1 V vs. Ag/AgCl. The use of stainless-steel electrode (SS316) as a counter electrode for electrochemical CO2RR is cost-effective and performs better than graphite electrode,
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