Fabrication and Mechanism Investigation of High-Porosity Micro-Arc Oxidation Functional Coating on Aluminum Foam Substrate

A high-porosity micro-arc oxidation (MAO) functional coating was fabricated on aluminum foam substrate through micro-arc oxidation technology, developing a structurally and functionally integrated bulk catalyst support material. Orthogonal experiments were employed to determine the optimal electrical parameters for achieving maximum coating porosity, with systematic investigations into the effects of electrolyte temperature and sodium tetraborate additives on pore characteristics. The phase composition, surface morphology, and elemental distribution of the porous coating were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Mercury intrusion porosimetry was applied to quantify the total pore area and pore size distribution. By means of secondary micro-arc oxidation, the catalyst was distributed in a gradient on the coating cross-section, which greatly improved the utilization rate of the catalyst. The formation mechanism of the porous coating was discussed, and the specific surface area of the fabricated catalyst-loaded materials was as high as (1.4~6.3) × 104 m2/m3, which provided a large number of attachment sites for catalyst particles.