Transition metal effects in the corrosion protection of electroplated zinc alloy coatings

Insight into anomalous hydrogen adsorption on rare earth metal decorated on 2-dimensional hexagonal boron nitride: a density functional theory study

Hydrogen interaction with metal atoms is of prime focus for many energy related applications like hydrogen storage, hydrogen evolution using catalysis, etc. Although hydrogen binding with many main group alkaline and transition metals is quite well understood, its binding properties with lanthanides are not well reported. In this article, by density functional theory studies, we show how a rare earth metal, cerium, binds with hydrogen when decorated over a heteropolar 2D material, hexagonal boron nitride. Each cerium adatom is found to bind eight hydrogen molecules which is a much higher number than has been reported for transition metal atoms. However, the highest binding energy occurs at four hydrogen molecules. This anomaly, therefore, is investigated in the present article using first-principles calculations. The number density of hydrogen molecules adsorbed over the cerium adatom is explained by investigating the electronic charge volume interactions owing to a unique geometrical arrangement of the guest hydrogen molecules. The importance of geometrical encapsulation in enhancing electronic interactions is explained.

Electrochemical deposition and characterization of zinc-nickel alloys deposited by direct and reverse current

Zn-Ni alloys electrochemically deposited on steel under various deposition conditions were investigated. The alloys were deposited on a rotating disc electrode and on a steel panel from chloride solutions by direct and reverse current. The influence of reverse plating variables (cathodic and anodic current densities and their time duration) on the composition, phase structure and corrosion properties were investigated. The chemical content and phase composition affect the anticorrosive properties of Zn-Ni alloys during exposure to a corrosive agent (3%NaCl solution). It was shown that the Zn-Ni alloy electrodeposited by reverse current with a full period T = 1 s and r=0.2 exhibits the best corrosion properties of all the investigated alloys deposited by reverse current.

Protective properties of epoxy coatings electrodeposited on steel electrochemically modified by Zn-Fe alloys

Epoxy coatings were electrodeposited on steel and steel modified by Zn-Fe alloys using the constant voltage method. Zn-Fe alloys were electrodeposited on steel at different current densities. The effect of the Zn-Fe alloy on the corrosion behavior of the epoxy coating was interpreted in terms of the electrochemical and transport properties. It was shown that the best properties, i.e. the largest values of the pore resistance and the smallest values of the coating capacitance, a longer period of almost constant Rp and Cp values, and the smallest diffusion coefficient of water through the epoxy coating, as well as the smallest amount of water absorbed inside the epoxy coating, were found for epoxy coatings on steel modified by a Zn-Fe alloy deposited at 4 A dm-2. During prolonged exposure to 3% NaCl, this Zn-Fe alloy significantly improves the corrosion stability of the epoxy coating: almost unchanged values of Rp and Rct were observed, due to the formation of a pseudo-passive layer of corrosion products, which is a good barrier to the transport of water, oxygen and electrolyte ions.

Electrochemical deposition and characterization of Zn-Fe alloys

Zn?Fe alloy electrochemically deposited on steel under various deposition conditions were investigated using anodic linear sweep voltammetry (ALSV) and X-ray diffraction (XRD) analysis for phase structure determination, energy dispersive X-ray (EDX) analysis for determination of chemical composition and polarization measurements and open circuit potential measurements for determination of corrosion properties. The influence of deposition current density on the chemical composition, phase structure and corrosion stability of Zn?Fe alloys was studied. It was shown that deposition current density strongly affects the corrosion stability of Zn?Fe alloys, while Zn?Fe alloy electrodeposited at 4Adm-2 exhibited the lowest corrosion rate.