Study On Performance Of Aluminum Coatings Prepared On NdFeB Surface From Ionic Liquid

Aluminum is called as green metal and widely used as ideal anti-corrosion material because of its high density.It is impossible to deposit aluminum in aqueous system,because the potential of aluminum is much lower than the potential of hydrogen in water.In recent years,with the far research in ionic liquids,aluminum film is deposited become the reality in the ionic liquids system.We will discuss the research in following four parts:?1?Corrosion behavior of magnet NdFeB in the ion liquid [AlCl₃-EMIC] during the electrodeposition of Al film is preliminary studied.Corrosion of magnet in both ion liquid and ethanediol were controlled both by anodic and cathodic reaction.In ion liquid,the open circuit potential of magnet was-0.663 V and the corrosion current density was 2.399×10^-5 A/cm²,which was faster than that in ethanediol.As the immersion time increased,there were obvious “pit” on the surface and some parts of grains fell off.The corrosion products were composed by the metal oxides of Nd and Fe.According to the analysis of SEM and AFM results,the contact time between NdFeB and ion liquid should be as short as possible,preferably not more than 10 min.?2?Deposition of aluminum thin film under the constant voltage.The deposition potential of aluminum is-0.615 V.The mechanism of aluminum thin film depositing on sintered NdFeB is described as instantaneous nucleation.It is proved that when the deposition potential is-0.6 V,the high number of active sites is conducive to the high dense and homogeneous surface.It is observed that the structure of the aluminum film is face-centered cubic structure and the structure doesn't change much with the increasing of over potential.The family of crystal planes of {200},{220} and {311} is dominant.The uniform and fine particles are good for forming the perfect anti-corrosion aluminum thin film.According to the electrochemical polarization curve analysis,we find that the corrosion current density of aluminum thin film preparing under the over potential of-0.6 V is the smallest in the whole series of experiments.?3?Deposition of aluminum thin film under the pulse voltage.The speed of process that ions from the solution diffuse to the cathode slows down with the decrease of pulse frequency.This situation may result in decrease of active sites on sintered NdFeB which will form the void structure film because of the large size of particles.It is observed that the structure of the aluminum film is face-centered cubic structure and the structure doesn't change much with the increasing of pulse voltage.The family of crystal planes of {200},{220} and {311} is dominant.Deposition of aluminum thin film is controlled by the diffusion process.High frequency will provide more time for diffusion process compared with low frequency which will contribute to the forming of smooth and high density aluminum thin film to improve the anti-corrosive function.?4?Preparation of aluminum thin films with different contents of additives.This article adopts the way that adding different contents of 2-chloro acid chloride to obtain various aluminum thin films.The ability of ant-corrosion and sizes of different particles are observed and their relationship has been discussed.This paper shows that the 2-chloro acid chloride can slow down the speed of deposition process which can contribute to form the small size of particles to improve the anti-corrosive function.