*2.1. MAO Process*

Titanium alloy Ti-6Al-4V rectangular specimens (Scope Metals Group Ltd., Bne Ayish, Israel, chemical composition shown in Table 1) with a surface area of 0.2 dm2 were ground using abrasive papers grits #280, #400, #600, #1000, #2400, and #4000, respectively, and then subjected to ultrasonic cleaning in acetone. The surface roughness is maintained to Ra = 3 μm after polishing.

**Table 1.** Chemical composition of the alloy Ti-6Al-4V.


MAO treatment was performed at 280 ◦C in the electrolyte with a eutectic composition of KNO3- NaNO3 (Sigma-Aldrich, St. Louis, MO, USA) with the mass % of 54.3 and 45.7, respectively. The electrolyte was held in a nickel crucible (99.95% Ni), which served as a counter-electrode. The surface ratio of anode-to-cathode was 1:30, the anodic current density was 250 mA/cm2, and the voltage was limited by the galvanostatic mode. The applied power supply had the following parameters: Imax = 35 A, Umax = 1000 V; current and voltage were pulsed with a square-wave sweep at a frequency of 1 Hz (ta = tk = 0.5 s) by a Digit-EL PG-872 pulse generator (Minsk, Belarus). The duration of the MAO treatment was 10 min, with a coating growth rate of 0.25 μm/min. Finally, the obtained specimens were air-cooled, rinsed with distilled water, and dried. The behavior of current vs. time and voltage vs. time was recorded by a Fluke Scope Meter 199C (Eindhoven, The Netherlands) (200 MHz, 2.5 GS s−1). A schematic of the detailed experimental setup is given in Figure 1.

**Figure 1.** Schematic of experimental setup: 1—ceramic stand; 2—heating element; 3—molten salt electrolyte; 4—specimen subjected to MAO treatment; 5—furnace with automatic temperature controller; 6—nickel crucible; 7,8—current connectors; 9—data logger; 10—pulse generator; 11—power supply.
