Alternating current oxidation of Ti–6Al–4V alloy in oxalic acid for corrosion resistant surface finishing

• Published in: SN applied sciences Vol. 2; no. 6; p. 1092
• Main Authors: Bandeira, Rafael Marinho, Rêgo, Galtiere Corrêa, Picone, Carlos Alberto, van Drunen, Julia, Correr, Wagner Rafael, Casteletti, Luiz Carlos, Machado, Sergio A. Spinola, Tremiliosi-Filho, Germano
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2020; Springer Nature B.V
• Subjects: Acid resistance; Acids; Alternating current; Applied and Technical Physics; Biocompatibility; Chemistry/Food Science; Corrosion; Corrosion resistance; Earth Sciences; Electrochemical impedance spectroscopy; Electrochemistry; Electrolytes; Engineering; Environment; Fluorides; Impedance; Materials Science; Materials Science: Materials for Modern Applications; Orthopedics; Oxalic acid; Oxidation; Oxide coatings; Research Article; Scanning electron microscopy; Spectroscopy; Surface finishing; Surface roughness; Thickness; Titanium alloys; Titanium base alloys; Toxicity; Transplants & implants; Ti–6Al–4V alloy; Corrosion; AC anodization; Oxide film
• ISSN: 2523-3963; 2523-3971
• DOI: 10.1007/s42452-020-2905-y

In this work, alternating current (AC) voltage ( V AC ) is applied to Ti–6Al–4V alloy in aqueous oxalic acid dihydrate solution to grow passive oxide films. The oxide layers are formed with V AC values in the range of 10–80 V. The resulting surface oxide layers have estimated thicknesses in the 100–500 nm range and are expected to have a two-layer structure consisting of a porous outer layer and a compact inner layer. The AC anodization process is demonstrated to have a slight effect on the surface roughness. Porous regions are observed on the films formed at lower and high AC voltages (i.e., V AC 10–30 and 80 V). The corrosion behavior in Ringer’s solution over 48 h of exposure is studied with electrochemical impedance spectroscopy. The AC anodized samples have higher impedance values than the untreated alloy by more than an order of magnitude. The oxides formed at V AC  = 40 − 70 V exhibit optimal resistance to corrosion as demonstrated by the overall impedance values, the polarization resistance values, and the capacitive behavior.