Effects of current density on commercially pure aluminum surfaces treated by PEO

Full text: Commercially pure aluminum surfaces were treated using electrolytic plasma (PEO) oxidation. A pulsed current source, applying a duty cycle of 50%, with a pulse width of 50μs was used. 30 mm x 2 mm (diameter x thickness) discs were anodically polarized on sodium silicate electrolyte for 12 minutes using current density at 9, 12 or 15A / dm². During each treatment, the voltage was monitored to determine the start of the rupture of the passive oxide layer. Microstructural, topographic and tribo mechanical characterizations were performed by X-ray diffraction, scanning electron microscopy (SEM), nanohardness and calotest. The main presence of the g-Al₂O₃ phase was observed, whose thickness was proportional to the current density used. While the porosity varied inversely with the current density, the same did not happen with the average pore size. In the latter, the mean diameter was 1.8 ± 0.5 μm, except for sample treated with 15 A / dm², whose value was 3.8 μm. These results are discussed in the light of PEO oxidation kinetics. (author)