1. Field of Invention
This invention relates to an electroplating process for depositing a single crystal metal layer on to a polycrystalline base metal from molten salts electrolyte and to the plated product.
2. Description of Prior Art
The present day electroplating processes deposit either polycrystalline or microcrystalline metal films on polycrystalline base metals.
In these processes, metal atoms produced by the electrochemical reactions during electroplating aggregate into metal clusters on the surface of a base metal, the clusters grow by incorporation of metal atoms into metal crystals, and metal crystals grow by incorporation into metal films.
The processes have two limitations. First, the aggregation or nucleation is rarely sufficient to fully cover the surface of a base metal; and second, the metal crystals that are produced have a tendency to accumulate dislocations or defects. This results in the formation of polycrystalline or microcrystalline metal films. Both these types of films are significantly imperfect.
A polycrystalline film has significant number of grain boundaries, and a microcrystalline film has substantial porosity. This makes them both permeable, and corrosion of base metals proceeds through these pores. Current electroplating processes are unable to avoid grain boundaries and micropores during deposition on polycrystalline base metals and require subsequent annealing.