A Kinetic Model for the Electrolytic Codeposition of α-Al ₂O₃ Particles with Co-Ni Alloy

A new kinetic model for the electrolytic codeposition of α-Al ₂O₃ particles with Co-Ni alloys on a rotation disk electrode is presented, which is based on the balance of force acting on a particle near the electrode surface. Adsorption strength of particles on the electrode was used to describe the force intensity of the interaction between the particles and the electrode. The critical adsorption strength was used to classify the adsorption into effective adsorption and non-effective adsorption. Only when the adsorption strength of a particle is above the critical value, the adsorption becomes effective and may be incorporated into the deposit. The probability of the particles being effective adsorption dependends on the average adsorption strength, which is effected by the force acting on the particle. A kinetic mathematical model relating the content of embedded particles to suspension concentration was deduced. This relationship was verified experimentally by the codeposition systems of α-Al ₂O₃/Co-Ni at the current density ranged from 1 to 20 A · dm^-2. The variation of the content of particles in deposits with current density is an overall balance of two opposing effects, which leads to a maximum on the particle content against current density curves. Some model parameters were determined also by comparing theory and experimental data.