Gas turbines are widely used for energy production. One of the critical points limiting their service life and performances is represented by hot corrosion taking place on the turbine blades. Nowadays, most of the research effort aims to extend the service life and operating temperature by means of enhanced corrosion resistant blades. That is based on the development of better thermal barrier coatings (TBC) and bond coats (BC). In particular, the bond coat, acting as a intermediate layer between the substrate and the TBC, is the most prone to thermal stress and corrosion; it is commonly made by aluminium (and its alloys) deposited by means of vacuum-based techniques (mainly PVD and pack cementation). These deposition methods are costly, energy consuming and does not allow the deposition of thick aluminum layers. On the contrary, aluminium can be electrodeposited from ionic liquids (ILs) leading to achieve thick, homogenelus and adhering coating at nearly room temperature saving time, energy and raw materials.. For such reasons, since their discovery, ILs have attracted a wide interest for their potential use as electrolytes, allowing the electrodeposition of metals that are impossible to reduce in aqueous media. In particular chloroaluminated ILs have been extensively and successfully investigated for the deposition of Aluminium and the process is under study for industrialization [http://scailup.eu]. Despite the discovery of this process in the nineties, nowadays aluminium electrodeposition from chloroaluminate ILs still maintains a number of open issues both on the side of fundamental science and technological aspects. The present communication aims both to assess the feasibility of the electrodeposition of aluminium from ionic liquids for an industrial application, and to shed some light on the aluminium electrodeposition process as concerning the effect of deposition parameters.
Thick Al-coatings (20 µm) were deposited on brass substrates at different temperature, potentials and stirring conditions. Then, the coatings morphology and phase composition was investigated by means of optical and scanning electron (SEM) microscopies, energy dispersive x-ray analysis (EDX), rugosimetry and X-ray diffraction.
Finally, electrochemical corrosion investigations (Open Circuit Potential recording and Potentiodynamic Polarization) were performed in order to correlate the coating structure and morphology with their anticorrosion performances.