Type II

Type II sulfuric acid anodizing forms a controlled aluminum oxide layer for corrosion resistance and dyeable color, with moderate thickness and good cosmetic finish.

Overview

Type II (sulfuric acid) anodizing grows an aluminum oxide layer on the surface to improve corrosion resistance, wear performance, and appearance. It’s the common “decorative anodize” used when you need black or colored parts, consistent cosmetics, and better durability than bare aluminum. The coating is integral to the base metal and can be sealed for improved corrosion performance.

Specify Type II for machined or sheet aluminum parts where color, light abrasion resistance, and a clean finish matter, and where tight post-finish dimensions aren’t driven by the coating itself. Key tradeoffs: anodize builds thickness (partly into the surface, partly outward), can shift critical dimensions, and may show alloy/heat-treat variation as color mismatch. Sharp edges, thread flanks, and electrical contact areas are common problem spots; mask them or plan secondary operations.

Common Materials

  • Aluminum 6061
  • Aluminum 7075
  • Aluminum 5052
  • Aluminum 2024
  • Aluminum 6063

Tolerances

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Applications

  • Black anodized instrument housings
  • Colored consumer electronics enclosures
  • Camera and sensor mounts
  • Aluminum brackets and panels
  • Knobs, levers, and handles
  • Optical and test equipment chassis

When to Choose Type II

Choose Type II when you need corrosion resistance plus a cosmetic, dyeable finish on aluminum at prototype through production volumes. It fits parts with moderate wear exposure and typical machined/sheet features where small dimensional shift from coating build is acceptable. Plan it early if you need masking, racking control, or color consistency across mixed alloys.

vs Type I

Pick Type II when you need dyed colors (especially black) and a more common, widely available anodize line with straightforward specs. Type II also tends to give a more uniform cosmetic finish on many commercial aluminum alloys when color matching is required.

vs Type III

Pick Type II when you don’t need hardcoat-level wear resistance or the thicker coating build that comes with it. Type II is usually better for cosmetic color, lower risk of dimensional shift on tight fits, and lower overall cost and lead time for general-purpose parts.

vs Powder coating

Pick Type II when you need a thin, metallic-looking finish that won’t chip like an applied film and can preserve fine features and markings. It’s also a good choice when you need the coating to follow edges and internal features without the orange-peel texture common in thicker organic coatings.

vs Electroless nickel plating

Pick Type II when you want a lightweight, aluminum-native finish with dye options and no added metal layer that can affect galvanic behavior or weight. Type II is often preferred for cosmetic parts where moderate protection is enough and you want a true anodized aluminum appearance.

Design Considerations

  • Call out anodize spec details: Type II class (dyed or clear), color, sealing requirement, and any cosmetic standard for visible faces
  • Identify and dimension critical fits with coating build in mind; avoid making anodized surfaces the only datum for tight assemblies
  • Avoid razor-sharp edges; add small chamfers/radii to reduce burn marks and color variation at edges
  • Specify masking for threads, press-fit bores, electrical contact pads, and grounding points; note acceptable mask lines
  • Keep mixed alloys on the same visible assembly to a minimum; if unavoidable, provide color targets and allow reasonable variation
  • Add non-cosmetic rack/hold points or designate hidden areas for contact marks to control appearance on show surfaces