A Novel Polishing Process for Ultra-Smooth Aluminum Surfaces via Anodizing in Sodium Metaborate

A novel ultra-smoothing process for aluminum surfaces was developed using porous alumina formation and subsequent oxide dissolution. submicron-scale periodic dimpled surface with an arithmetic mean roughness of 31.5 nm prepared by anodizing in etidronic acid solution. This specimen then anodized a sodium metaborate (NaBO 2 ) solution to form unique film extremely flat barrier layer, which differs from the typical hemispherical layer. The outer layer became thicker time during anodizing, whereas thickness smoothness inner were maintained without breakdown. As chemically removed CrO 3 /H PO 4 solution, smooth exposed. drastically decreased 0.5 short-term 15 min slightly further anodizing. result, ultra-smooth measuring 0.4 roughness, is much smaller than that electropolished (1.3 nm), successfully obtained via NaBO Our smoothing compared conventional processes such as electropolishing formation.