Ceria Particles as Efficient Dopant in the Electrodeposition of Zn-Co-CeO2 Composite Coatings with Enhanced Corrosion Resistance: The Effect of Current Density and Particle Concentration.

Novel Zn-Co-CeO2 protective composite coatings were deposited successfully from chloride plating solutions. Two different types of ceria sources were used and compared: commercial ceria powder and home-made ceria sol. Electrodeposition was performed by a direct current in the range of 1-8 A dm-2. Two different agitation modes were used and compared, magnetic stirring and ultrasound-assisted stirring (US). The influence of magnetic stirring on the stability of the related plating baths was evaluated via a dynamic scattering method. The results pointed to better stability of the prepared ceria sol. The morphology of the composite coatings was examined by scanning electron microscopy (SEM), and particle content was determined by energy-dispersive X-ray spectroscopy (EDS). The results showed that the increase in the deposition current density was not beneficial to the coating morphology and particle content. The corrosion behavior of the Zn-Co-CeO2 composite coatings was analyzed and compared by electrochemical impedance spectroscopy and polarization resistance. The ultrasound-assisted electrodeposition at small current densities was favorable for obtaining composite coatings with enhanced corrosion stability. The protection was more effective when US was applied and, additionally, upon utilization of ceria sol as a particle source, which was revealed by higher polarization resistance and greater low-frequency impedance modulus values for sol-derived composite coatings deposited under ultrasound.

Full Optimization of an Electroless Nickel Solution: Boosting the Performance of Low-Phosphorous Coatings.

Univariate and multivariate optimizations of a novel electroless nickel formulation have been carried out by means of the Taguchi method. From the compositional point of view, adjustment of the complexing agent concentration in solution is crucial for fine-tuning free Ni2+ ions concentration and, in turn, the mechanical properties of the resulting coatings. The Ni (II) concentration and the pH are the main parameters which help restrict the incorporation of phosphorous into the Ni layers. On the other hand, the stirring rate, the pH and the reducing agent concentration are the most influential parameters for the corrosion resistance of the coatings. Multivariate optimization of the electrolyte leads to a set of optimized parameters in which the mechanical properties (hardness and worn volume) of the layers are similar to the optimal values achieved in the univariate optimization, but the corrosion rate is decreased by one order of magnitude.

Electroless Palladium-Coated Polymer Scaffolds for Electrical Stimulation of Osteoblast-Like Saos-2 Cells.

Three-dimensional porous scaffolds offer some advantages over conventional treatments for bone tissue engineering. Amongst all non-bioresorbable scaffolds, biocompatible metallic scaffolds are preferred over ceramic and polymeric scaffolds, as they can be used as electrodes with different electric field intensities (or voltages) for electric stimulation (ES). In the present work we have used a palladium-coated polymeric scaffold, generated by electroless deposition, as a bipolar electrode to electrically stimulate human osteoblast-like Saos-2 cells. Cells grown on palladium-coated polyurethane foams under ES presented higher proliferation than cells grown on foams without ES for up to 14 days. In addition, cells grown in both conditions were well adhered, with a flat appearance and a typical actin cytoskeleton distribution. However, after 28 days in culture, cells without ES were filling the entire structure, while cells under ES appeared rounded and not well adhered, a sign of cell death onset. Regarding osteoblast differentiation, ES seems to enhance the expression of early expressed genes. The results suggest that palladium-coated polyurethane foams may be good candidates for osteoblast scaffolds and demonstrate that ES enhances osteoblast proliferation up to 14 days and upregulate expression genes related to extracellular matrix formation.

Robust Aluminum Electrodeposition from Iionic Liquid Electrolytes Containing Light Aromatic Naphta as Additive.

Aluminum electrodeposition can be carried out from several ionic liquid electrolyte formulations. Nevertheless, this plating process has not been industrialized so far because of the durability of the electrolytes and because the Al coatings obtained are non-fully homogeneous in terms of coating morphology and thickness distribution. In this work we electrodeposited Al coatings from a 3-butyl-1-ethylimidazolium tetrachloroaluminate electrolyte additivated with increasing concentrations of a new cost-effective additive: light aromatic naphtha solvent. Firstly, electrolytes were characterized by cyclic voltammetry, where changes in the electrochemistry of the process were identified. Then, surface characterization showed that Al coatings morphology turned out to be smoother, more homogeneous and more compact with increasing additive concentration. Furthermore, the process was scaled up to flat plates of 18 cm2 area and also on 25 cm2 parts designed with straight corners to demonstrate both the optimization of the electrolytic bath performance and its throwing power enhancement.