The advanced coating material TiAlN has higher corrosion resistance than TiN without Al content. TiAlN films are conventionally prepared by sputtering using a target with fixed Ti and Al composition. We prepared Ti_1-xAl_xN films using a dynamic ion mixing apparatus with two electron-beam evaporation sources for Ti and Al deposition. Ti and Al contents of films were changed by independently controlling the evaporation rate of the two sources at a constant N concentration of 30%. This system controls the film Ti and Al composition ratio (value x) precisely.
Electrochemical film properties were measured using AC impedance and a fast Fourie transform analyzer. The measurement cell was constructed from two Ti_1-xAl_xN film samples coated on stainless steel used as electrodes in an HCl solution of 1mol/dm³. The equivalent circuit of the cell based on a typical parallel circuit, took film resistance R_f and capacity C_f into consideration and was determined by P-Spice simulation. Electrochemical properties were evaluated using interfacial resistance R_t, electrical double-layer capacity C_d and time constant R_t×C_d parameters. The Ti and Al composition ratio for optimum corrosion resistance was x=03.