Aluminum and its alloys have a wide range of applications due to their excellent properties, such as low density and high corrosion resistance. The electrochemical deposition of Al-based materials is not possible from aqueous solutions due to their rather negative Nernst potential (-1,66 V vs. SHE). There are few industrial processes for plating of aluminum, e.g. the SIGAL process. However, those processes usually are based on expensive, highly flammable and/or volatile substances, leading to high requirements regarding the technical equipment.

The deposition from ionic liquids (ILs) opens new possibilities for industrial processes. The ILs have large electrochemical windows (> 3 V) and permit high solubility for metal salts, allowing the electrochemical deposition of base metals, like aluminum, and a considerable number of its alloys. Furthermore, there is no hydrogen embrittlement of steel substrates in ILs due to their aprotic character, and the deposition of Al-based films is possible at room temperature.

Al-based materials are promising candidates for corrosion protection of steel and could replace environmentally harmful coatings, such as cadmium. ILs are still quite expensive, but their price continuously decreased during the last years, making an industrial process more interesting.

This paper will discuss recent results from the authors’ lab on the deposition of aluminum alloys from imidazolium based ILs. Binary alloys of aluminum with Zn, Sn and Cr were deposited and investigated. The deposition process regarding precursor concentration, process parameters, properties of the deposits (composition, structure, morphology) and corrosion behaviour in aqueous sodium chloride solution will be discussed. Furthermore, it will be shown that the pre-treatment of the used steel substrates plays a crucial role to obtain well adhering layers.