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Anodizing Technology

How anodizing works and how our process runs.

EF Technology provides aluminum anodizing surface treatment.

Anodizing is a surface treatment that converts the aluminum surface into an oxide coating by an electrochemical reaction. The coating is integral with the base material, does not peel, and improves corrosion resistance, wear resistance and electrical insulation. EF Technology runs the entire hard and soft anodizing process on its own lines.

The Coating Is a Converted Layer of the Material Surface

Cross-section of anodic coating growth Relative to the original surface line, about half of the coating penetrates into the base metal and about half grows outward. The coating consists of a thin barrier layer and a thick porous layer. Sulfuric acid bath Aluminum base (before) Original surface Growth ≈ t/2 (size increase) Penetration ≈ t/2 (metal consumed) Coating thickness t (Type III ≈ half/half) Porous layer: one pore per hex cell, where dye enters Barrier layer: thin, dense, non-porous Aluminum base (after) Oxidation occurs at the metal/oxide interface and advances downward Anode (part): 2Al + 3H₂O → Al₂O₃ + 6H⁺ + 6e⁻ Cathode: 2H⁺ + 2e⁻ → H₂↑
Coating growth cross-section — from the original surface line, half grows into the material and half grows outward

Plating adds a different metal on top of the material, but an anodic coating is a layer in which the aluminum itself is converted to aluminum oxide. The coating grows half into the material and half outward from the original surface line, so for parts with dimensional tolerances, a dimensional increase of half the coating thickness is accounted for at the design stage. The regular fine pores in the coating are closed in the final sealing step to complete corrosion resistance.

Process Flow

Select a step to see its description and illustration.

01

Racking

Parts are mounted on dedicated racks that fix the current-carrying contact points and the orientation of each part.

Anodizing passes current through the part itself, so the contact points between rack and part form the electrical path. The position, number and layout of contacts determine coating thickness distribution and where contact marks appear. EF Technology designs a dedicated rack for each part and places contacts on non-functional areas of the drawing.

For parts that need selective treatment, the jig sets the contact position and masks the areas to be left untreated. EF Technology holds a registered patent for a plating jig device with a simple marking function.

Contact marks and masking
Contact pointDedicated rack · contact positions and part orientation recorded

Benefits of Anodizing

Corrosion resistanceProtects the material in corrosive environments.
Wear resistanceHard coatings raise surface hardness.
Electrical insulationApplied to parts that require electrical insulation.
AppearanceA uniform, clean surface finish.