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Paint treatment

Table of Contents

Definition

Anodizing is an electrochemical surface finishing process exclusively for aluminum and its alloys. By placing aluminum workpieces as the anode in an electrolyte solution with applied direct current, a hard, dense, self-adherent aluminum oxide film grows on the metal surface. This protective oxide layer cannot peel off like paint or powder coating.

Core Working Principle

When electric current passes through the electrolyte, oxygen ions combine with aluminum atoms on the part’s surface to form aluminum oxide (Al₂O₃). The generated oxide film has two layers: a porous outer layer for dye absorption and a compact inner barrier layer for corrosion resistance. After anodization, sealing treatment closes the micropores to lock in color and boost protection.

Main Anodizing Types

Type I: Chromic Acid Anodizing

Thin, ultra-light oxide film. Primarily used for aerospace precision parts, rarely for decorative appearance due to dull gray tone.

Type II: Sulfuric Acid Decorative Anodizing

The most widely used standard anodizing. Medium film thickness (8–25μm), supports full color dyeing (black, silver, gold, blue, red, custom tones). Ideal for consumer electronics, logo plaques, hardware and decorative prototypes.

Type III: Hardcoat / Hard Anodizing

Extra thick, ultra-hard oxide layer (25–100μm). Outstanding wear, abrasion and corrosion resistance. Applied to mechanical moving parts, molds, automotive components and industrial equipment.

Standard Production Workflow

CNC Machining / Die Casting → Pre-treatment (Grinding / Sandblasting / Brushing / Polishing) → Degreasing & Etching → Sulfuric Acid Anodizing → Dyeing (optional) → Sealing → Finished Parts

Key Advantages

  1. Exceptional Corrosion Resistance The continuous aluminum oxide film isolates the substrate from air and moisture, far superior to bare aluminum.
  2. Superior Hardness & Wear Resistance Hard anodized surfaces outperform most painted or powder-coated finishes, resisting scratches and abrasion in long-term use.
  3. Rich Customizable Decorative Effects Compatible with pre-finishes including brushing, mirror polishing and sandblasting; can be dyed into various solid colors for premium metallic aesthetic.
  4. Non-Peeling, Eco-Friendly Finish The oxide layer chemically bonds with the base aluminum, never chips or delaminates. No toxic solvent emissions during processing.
  5. Electrical Insulation The dense oxide film blocks electric conduction, suitable for electronic component housings.

Applicable Materials

Only aluminum, aluminum alloy and die-cast aluminum parts. Not compatible with steel, stainless steel, copper or plastics.

Limitations

  1. Exclusive to aluminum materials; cannot be applied to other metals or plastics.
  2. Hard anodizing slightly increases part dimensions, requiring tolerance adjustment during machining.
  3. Color options are limited compared to liquid painting and powder coating; metallic pearlescent textures are harder to achieve.

Surface treatment resources

Frequently Asked Questions

  To shorten the delivery cycle of CNC workpieces, we start with the documents submitted by customers. Please provide complete and clear 2D drawings, 3D models, dimensional tolerances, surface requirements, and processing specifications, and specify special materials, surface treatments, and assembly standards. Avoid incomplete drawings, ambiguous markings, and version confusion.
Complete documents enable direct programming, order splitting, and production scheduling, cutting down repeated confirmation and supplementary work. Customers are also advised to finalize order quantity, delivery schedule, and special requirements in advance. Eliminating repeated communication and rework risks at the source accelerates the whole process and effectively shortens the overall lead time.

  With 12 years of expertise in CNC machining, YUEYI stands out from other manufacturers and middlemen. Our factory covers an area of 4,000 mu and is equipped with over 100 processing machines. We achieve a machining precision up to 0.001 mm, capable of producing high-precision components. Backed by standardized production management, our on-time delivery rate reaches 98%. As a direct manufacturer with full in-house production capacity, we control every production link without outsourcing. We deliver consistent quality, outstanding precision and reliable lead time, making us your trustworthy partner for CNC precision machining.

  Fast delivery is one of our key strengths. For 3D printing orders, we support delivery within 3 days, ideal for rapid prototyping and urgent sample requests. For regular CNC machining projects, the standard lead time is around 3 weeks.
We manage the whole process in-house, from drawing review and process planning to production, quality inspection, and shipment, with no intermediate links. Equipped with complete facilities and an experienced team, we reliably fulfill both urgent sample orders and mass production. We guarantee stable lead time and consistent quality to keep your projects on track.

  We offer a full range of surface treatments with rich color options. Our services include anodizing, powder coating, spray painting, electroplating, wire drawing, sandblasting, and polishing. Anodizing features various colors and strong anti-corrosion performance for aluminum parts. Powder coating and spray painting come with extensive color selections and durable coatings. Electroplating enhances luster and rust resistance. Wire drawing creates fine linear textures, while sandblasting delivers a matte finish. Polishing achieves a bright and smooth surface. All finishes can be customized in colors and styles to match your application needs.

  Yes, we fully provide complete material certificates and relevant test reports for all CNC-machined parts. All raw materials are sourced from qualified suppliers with authentic documentation. We can offer material certifications, dimension inspection reports, and quality test records upon request. Every product is strictly inspected before delivery. These official documents fully guarantee material compliance and product quality, supporting your quality audit and project requirements.

  We take strict quality control measures in advance to prevent non-conforming products. Every workpiece is fully inspected dimensionally and visually during and after production to ensure full compliance with design drawings and specifications.
In the rare case of non-compliant items, we will take immediate responsibility. We will promptly confirm the issues with you, then arrange free rework or remanufacturing as required. All related costs will be borne by us. We will also analyze the root cause to optimize our processes and avoid similar problems recurring. Our goal is to deliver qualified products steadily and safeguard your project progress.

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