Is Barrier Layer Responsible for Cellular Structure Of Aluminum Oxide Film Anodized in Sulfuric Acid?

摘要

Increasing AC voltage in DC+AC process can reduce DC voltage to ～7 VDC that creates a strong enough electric field, forming a barrier layer with three areas. The closest to aluminum area has composition Al{sub}(2+q)O{sub}3 with higher concentration of aluminum ions. Above it there is pure dielectric: Al{sub}2O{sub}3-area. Area Al{sub}2O{sub}(3+p) close to electrolyte has higher concentration of oxygen ions. A weak (for example, boric) acid does not dissolve barrier layer. A strong (for example, sulfuric) acid finds a spot and dissolves barrier layer until the lowest area Al{sub}(2+q)O{sub}3 surrounding the spot is reached and flooded with oxygen ions. These ions transform Al{sub}(2+q)O{sub}3 into Al{sub}2O{sub}3 that builds up wall around the spot, forming a pore. Each spot is complemented equidistantly with six spots, building hexagonal cells with a pore in the center of each cell.