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How is the anodizing treatment of standard aluminum profiles carried out?
1. Pretreatment stage
Degreasing and cleaning
Use alkaline solution (such as NaOH or special degreasing agent) to remove surface oil stains, temperature 50-60℃, time 5-10 minutes.
Alkaline etching treatment
Immerse in 10% NaOH solution (60℃) to corrode the surface and remove the natural oxide layer for 30-120 seconds.
Neutralization and lightening
Nitric acid (10-30%) or mixed acid solution neutralizes the residual alkali solution and restores the metallic luster for 1-3 minutes.
2. Anodizing stage
Electrolytic cell configuration
Electrolyte: sulfuric acid (15-20%), oxalic acid or chromic acid solution (select according to needs).
Temperature: 18-22℃ (sulfuric acid system), voltage 12-20V DC.
Electrode: aluminum profile as anode (+), lead plate/stainless steel as cathode (-).
Oxidation reaction
Anodic reaction after power on: 2Al + 3H₂O → Al₂O₃ + 6H⁺ + 6e⁻
Oxide layer growth rate: 0.5-2μm/minute, thickness is usually 5-25μm (industrial profiles are mostly 10-15μm).
3. Post-processing stage
Sealing treatment
Hot water sealing: Soak in 90-100℃ deionized water for 20-30 minutes, alumina hydrates to boehmite (AlOOH), and seals the micropores.
Cold sealing: Nickel salt solution (containing NiF₂) is sealed at room temperature, suitable for dyeing post-processing.
Dyeing/electrolytic coloring (optional)
Adsorption dyeing: Immerse the oxidized porous layer in organic dyes (such as black, gold).
Electrolytic coloring: Secondary electrolysis in a metal salt solution (such as SnSO₄) to generate a more weather-resistant colored oxide layer.
Surface treatment and color
Processing technology: fluorocarbon spraying, polyester powder spraying, wood grain transfer, anodizing, frosting, electroplating, etc.
Color options: white, black, gray, imitation wood grain, stone grain, gold, champagne gold, etc., support customized patterns.
