We used 60 strip-shaped samples of tantalum with the following dimensions: 7 mm wide, 11 mm long, and 0.01 mm thick (Kurt J. Lesker Company—USA, 99.95 % purity). The samples were washed in distilled water and placed in an ultrasonic tank containing acetone (Ultra Sonic-1440 Plus—Odontobrás, Ribeirão Preto/SP, Brazil) to remove residues. Then, they were divided into four groups: in group 1 (control), tantalum received no treatment; in group 2, strips of tantalum were treated using PEO for 1 min; in group 3, tantalum strips were treated using PEO for a 3-min exposure; and in group 4, tantalum strips were treated using PEO for a 5-min exposure. This is shown in Table 1.

Then, the samples were washed with anhydrous ethyl alcohol (99.3° INPM, BM Anhydrous Alcohol Cycle, Serrana/SP).

A self-organized porous surface of tantalum (Ta) was obtained through oxide formation of Ta using the PEO process. The anodizing process was conducted using an electrolytic solution containing 0.2 mol calcium acetate Ca (CH₃CO₂)₂ H₂O and 0.02 mol sodium glycerophosphate (hydrated salt) C₃H₇Na₂O₆P diluted in 1-L deionized water [10–13].

Following Yerokhin [14], in order to perform the anodizing process, Ta sample surfaces were previously cleaned in ethanol and distilled water and then air-jet dried. Then, the samples were immersed in the electrolyte solution and connected to an open circuit, where Ta was the anode (connected to the positive pole), and to a platinum plate functioning as a cathode (connected to the negative pole). Samples were treated in a reactor, driven by an electric system consisting of the following components: AC power source with variable output voltage, a transformer, a rectifying circuit, a circuit breaker, an ammeter, and a voltmeter. An oscilloscope was used to verify the waveform after rectification [12]. The processing system is composed of the electrode support and the electrolyte tank [12]. During treatment, the temperature of the electrolytic solution was measured by a portable thermometer.