Surface Treatments for 6061 Aluminum Profiles

Published Time:

2026-08-14

Author:

Guantian Aluminum

6061 aluminum alloy is a heat-treatable strengthened alloy. It features excellent formability, weldability and machinability with moderate strength, and retains favorable workability after annealing. Its main alloying elements are magnesium and silicon, which form Mg₂Si precipitates. Appropriate manganese and chromium can offset the adverse effects of iron. Small amounts of copper or zinc may be added to boost strength without obvious deterioration of corrosion resistance. Minor copper is used in conductive grades to counteract negative impacts of titanium and iron on electrical conductivity. Zirconium or titanium serves to refine grains and control recrystallization structure. Lead and bismuth can be added to improve machinability. The solid solution of Mg₂Si in aluminum enables artificial age hardening. Overall, 6061 aluminum delivers moderate strength, good corrosion resistance, reliable weldability and satisfactory anodizing performance.

Sand blasting is primarily applied for surface cleaning. Before painting or powder coating, sand blasting increases surface roughness to improve coating adhesion, though its effect is limited compared with chemical pretreatment.

Two mainstream coloring processes are available for aluminum: anodizing coloring and electrophoretic coloring. Various colors can be formed on the oxide film to meet practical requirements. For instance, black finish is commonly adopted for optical instrument parts, and golden color for commemorative badges.

Conductive oxidation (chromate conversion coating) is suitable for applications requiring both corrosion protection and electrical conductivity.

Chemical oxidation generates a relatively thin oxide film ranging from 0.5 to 4 micrometers. The porous and soft film possesses good adsorption capacity and can act as the base layer for organic coatings. Nevertheless, its wear resistance and corrosion resistance are inferior to anodized films. Based on solution properties, chemical oxidation of aluminum alloys can be divided into alkaline oxidation and acidic oxidation. According to film characteristics, the coatings include oxide films, phosphate films, chromate films and chromate-phosphate films.

Electrochemical anodizing requires simple equipment and easy operation, with high production efficiency and no power consumption. It is applicable to workpieces of various sizes and shapes. The conventional anodic oxide film thickness ranges from 5 to 20 micrometers, while hard anodized films can reach 60 to 200 micrometers. The film boasts high hardness, outstanding heat resistance and insulation performance, superior corrosion resistance compared with chemical oxidation films, as well as porous structure with strong adsorption capacity.

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