Electrodeposition mechanism and corrosion behavior of multilayer nanocrystalline nickel-tungsten alloy

Enhancing Anticorrosion Resistance of Aluminum Alloys Using Femtosecond Laser-Based Surface Structuring and Coating

We report a robust two-step method for developing adherent and anticorrosive molybdenum (Mo)-based coatings over an aluminum (Al) 6061 alloy substrate using a femtosecond (fs) laser. The fs laser nanostructuring of Al 6061 alloy in air gives rise to regular arrays of microgrooves exhibiting superhydrophilic surface properties. The microstructured surface is further coated with an Mo layer using the fs-pulsed laser deposition (fs-PLD) technique. The combination of the two femtosecond laser surface treatments (microstructuring followed by coating) enabled the development of a highly corrosion-resistant surface, with a corrosion current of magnitude less than that of the pristine, the only structured, and the annealed alloy samples. The underlying mechanism is attributed to the laser-assisted formation of highly rough hierarchical oxide structures on the Al 6061 surface along with post heat treatment, which passivates the surface and provide the necessary platform for firm adhesion for Mo coating. Our results reveal that the corrosive nature of the Al-based alloys can be controlled and improved using a combined approach of femtosecond laser-based surface structuring and coating.

A study of degradation behaviour and biocompatibility of Zn-Fe alloy prepared by electrodeposition

Zinc is a biodegradable metal, which exhibits more moderate biodegradability than magnesium and iron, so that it has great application potential in the field of biomedical materials. Alloying of zinc and iron may lead to producing a new type of implant material Zn-Fe alloy, which might be able to meet the requirements for a moderate degradation rate. However, due to the huge difference in the melting point between zinc and iron, the preparation of Zn-Fe alloy is quite challenging and hence rarely reported. In this study, we show that Zn-Fe alloys can be successfully prepared by electrodeposition technology. The microstructures, composition, degradation properties and biocompatibility of the Zn-Fe alloys were systematically studied. The results showed that the content of iron in the alloys ranged from 0 to 8 wt%, depending on the concentration of Fe ions and the current density. In the alloys, the major's phases were η, δ and Г₁, and they were mainly affected by the ion concentration in the electrolyte. In the in vitro immersion tests, the Zn-Fe alloy ZF2-1 showed the highest immersion corrosion rate, while ZF3-1 showed the highest electrochemical corrosion rate. Moreover, we found that the corrosion rates of the alloys were significantly higher than that of the pure Fe. In the in vivo experiments, we confirmed that the Zn-Fe alloy possessed good biocompatibility. These results demonstrate that the electrodeposition technology is a good method to prepare Zn-Fe alloys, and the Zn-Fe alloys prepared by this method are potentially promising materials for biomedical applications.

Influence of Positional Isomeric Spacers of Naphthalene Derivatives on Ni-W Alloy Electrodeposition: Electrochemical and Microstructural Properties

Herein, Ni-W alloy matrixes were successfully fortified with two salen-type Schiff bases 1-((E)-(2-((E)-(2-hydroxynaphthalen-1-yl)methyleneamino)phenylimino)methyl)naphthalen-2-ol (OPD) and 1-((E)-(2-((E)-(2-hydroxynaphthalen-1-yl)methyleneamino)phenylimino)methyl)naphthalen-2-ol (PPD) as additives, of similar molecular structure but varied isomeric spacers, using a facile direct current electrodeposition technique. The resulting coatings from the additive-introduced reaction system were termed as Ni-W/OPD and Ni-W/PPD throughout the study. The deterioration process (0.5 M H2SO4), surface properties, elemental composition, functional groups, and structurs of the resultant coatings were analyzed by means of Tafel and electrochemical impedance spectroscopy, field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction (XRD). The bare Ni-W alloy deposition resulted in a loose microstructure with higher porosity density (12.2%), while that of additive-doped plating electrolytes resulted in a compact and dense microstructure with lesser porosity density (6.3%) and minimal porosity density (3.7%) as for Ni-W/OPD and Ni-W/PPD alloy coatings, respectively. Improved corrosion parameters presented superior corrosion characteristics of Ni-W alloy coatings from an additive (PPD)-induced bath, i.e., Ni-W/PPD. Synergetic adsorption of imine groups (N atoms), hydroxyl groups (O atoms), and aromatic electron clouds and reduction in steric hindrance produced by a larger isomeric spacer strengthened the surface adsorption of additives, yielding a fine nanocrystalline Ni-W coating with reduced porosity and well-refined grains, implying the outstanding shielding effect. Results of FESEM, AFM, and XRD analyses revealed a complete cohesion between two neighboring islands, resulting in a fine planar structure with minimal coating defects for Ni-W/PPD coatings, authenticating the corrosion parameters.