Experimental characterization and theoretical treatment of alloys and composites that undergo anomalous codeposition.

摘要

Experimental and theoretical studies were carried to determine the electrodeposition characteristics of iron-nickel (Fe-Ni) and zinc-nickel (Zn-Ni) alloys and their SiO{dollar}sb2{dollar} composites. The effect of various experimental parameters such as the solution agitation, electrode polarization, and electrolyte concentration on the composition and quality of the deposit was determined. The corrosion rates of the resultant Fe-Ni-SiO{dollar}sb2{dollar} composites were obtained as a function of the SiO{dollar}sb2{dollar} composition in the deposit. A mathematical model was developed to describe the anomalous codeposition of Fe-Ni alloys and Fe-Ni-SiO{dollar}sb2{dollar} composites under potentiostatic conditions. The model took into account the solution chemistry, mass transport in the diffusion layer, surface electrochemical reactions, and a two-step potential assisted adsorption-inclusion mechanism for the inclusion of inert particles. This model can be used to predict the polarization behavior, partial current densities, concentration profiles at steady state, and alloy composition as a function of the applied electrode potential.; Hydrogen permeation studies were carried out on Zn-Ni alloys and Zn-Ni-SiO{dollar}sb2{dollar} composites under applied polarization and corroding conditions in order to determine the feasibility of using these coatings as hydrogen permeation inhibitors. A mathematical model was developed for the characterization of hydrogen permeation into metals and alloys under corroding conditions. The model requires a knowledge of the corrosion rate of the given metal or alloy in solutions of various H{dollar}sp{lcub}+{rcub}{dollar} concentrations. It provides quantitative values of rate constants of the hydrogen discharge, recombination and adsorption reactions. This model can serve as a diagnostic criterion for determining the effectiveness of various metals and alloys as hydrogen permeation inhibitors and can be used for evaluation of hydrogen entry inhibition efficiency. The experimental hydrogen permeation data obtained for Zn-Ni coated iron were analyzed using the model and the results were compared with the hydrogen permeation characteristics of bare iron.