Type II

Type II sulfuric acid anodizing forms a thin, dyeable oxide layer on aluminum for decorative finish, moderate corrosion resistance, and improved wear at low cost.

Overview

Type II sulfuric acid anodizing creates a controlled aluminum oxide layer, typically 0.0002–0.001" thick, on aluminum parts. It improves corrosion resistance, provides an excellent base for dyes, and delivers a consistent, cosmetic finish. It’s common for clear and black anodize on machined, extruded, or fabricated aluminum components.

Use Type II when you need a decorative, uniform finish with moderate wear resistance and reliable corrosion protection in normal environments. It suits most commercial, consumer, and light industrial parts, especially where color and appearance matter. Thickness is limited compared to hardcoat, so it’s not ideal for high-abrasion or heavy load-bearing surfaces. The process slightly changes dimensions and can highlight machining marks, so surface prep and dimensional allowances matter. Cost is generally low per part, especially for batch runs, but masking, tight color control, and complex racking drive cost up.

Common Materials

  • Aluminum 6061
  • Aluminum 5052
  • Aluminum 7075
  • Aluminum 2024
  • Aluminum 6082

Tolerances

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Applications

  • Electronics enclosures and housings
  • Camera and optical equipment bodies
  • Heat sink extrusions
  • Consumer hardware and appliance trim
  • Motorcycle and bicycle components
  • Hydraulic and pneumatic valve bodies

When to Choose Type II

Choose Type II anodizing when you need cosmetic aluminum finishes with consistent color, branding dyes, and good corrosion resistance in standard service environments. It fits small to large batch volumes where appearance and moderate wear resistance matter more than extreme durability. It works best for machined or extruded aluminum parts with stable alloys and non-critical dimensional changes on anodized surfaces.

vs Type I

Choose Type II instead of Type I when you need stronger corrosion resistance, thicker coatings, or dyed/color finishes on aluminum. Type II also gives more consistent appearance and durability for consumer and industrial parts that see regular handling or mild abrasion.

vs Type III

Choose Type II instead of Type III when cosmetic finish, color options, and lower cost matter more than maximum wear or thickness. Type II is better for decorative parts, general housings, and components that don’t see heavy sliding contact or high pressures but still need a clean, protective finish.

vs Powder coating

Choose Type II anodizing over powder coating when you need a thin, dimensionally tight finish that preserves fine features, threads, and heat transfer surfaces. Type II also bonds directly to the aluminum substrate, so it will not chip or flake like thicker organic coatings in edge or sharp-corner areas.

vs Chromate conversion coating

Choose Type II instead of chromate conversion when you need a harder, more abrasion-resistant surface and a fully finished cosmetic look. Type II is better for visible parts and surfaces where scratch resistance and clean appearance are more important than ultra-low thickness or maximum electrical conductivity.

vs Painting

Choose Type II anodizing over painting when you want a durable, integrated oxide layer that resists scratching and won’t peel. Type II delivers more consistent metallic appearance, better UV stability for many colors, and thinner buildup that preserves precise machined features and fits.

Design Considerations

  • Specify coating thickness (e.g., 0.0004–0.0008" total) and whether dimensions are before or after anodize so shops can adjust machining allowances
  • Call out masking requirements only where functionally necessary; masking small features, sealing surfaces, and threaded areas adds setup cost and risk
  • Avoid extremely tight tolerances on anodized fits; allow clearance for coating growth or leave critical bores and threads un-anodized and post-machined if needed
  • Choose alloys with good anodizing behavior (e.g., 5xxx/6xxx); high-copper or high-silicon alloys can streak, pit, or give uneven color
  • Define color (Pantone/RAL or sample) and gloss level, and accept realistic batch-to-batch variation, especially across different alloys or thicknesses
  • Provide clear racking and contact-area guidance on non-cosmetic surfaces so the shop can fixture parts without affecting critical or visible areas