Graining technology by electrolytic etching on the surface of aluminum alloys

Abstract

The electrolytic etching solution of an aluminum alloy is comprised of the species forming a barrier layer on the surface of the aluminum alloy and the species etching the barrier layer. The experiments showed that in the sodium metaboricate—boric acid electrolysis system with sodium metaboricate as the main component, sodium carbonate as the etchant and sodium phosphate as the enhancing bond-agent—the electrolytically etched graining on the surface of the aluminum alloy are true to life, the depth of the mark is moderate. After the electrolytically etched graining is anodized and is then submitted to electrolytic coloring, the color comparison is obvious, and extremely similar to wood graining. The XRD diagrams show that the electrolytically etched surface of the aluminum alloy consists of aluminum and alumina, which mainly localized in the graining zone and exists in α-Al 2O 3 and γ-Al 2O 3. Having been anodized, SO 4 2− is introduced into the oxidized film; the pore density and the pore diameter of the multi-porous layer of the oxidized film in the graining zone are bigger than those in the grainless zone. Thus the inner depositing amounts in the micro-pores of the oxidized film in the graining zone are big, which would show dark color.