Type II clear anodize

Clear Anodized Aluminum

Clear anodize is the default protective finish for machined aluminum: a Type II sulfuric-acid film, 8–15 µm thick, that locks in the metallic look while making the surface hard, corrosion-resistant, and wipeable.

If a part needs to survive handling and humidity without changing how it looks or measures, this is the finish that does it for the least money.

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What this finish is

Grown from the part, not painted on

Anodizing converts the aluminum surface itself into aluminum oxide by passing current through the part in a sulfuric acid bath. The film grows both into and out of the metal — roughly half in, half out — which is why it can't peel like paint and why it slightly changes dimensions.

'Clear' means no dye is added before the pores are sealed: the film is transparent, and the part keeps its metallic silver tone with a subtle satin shift. Sealing in hot water or nickel acetate closes the porous structure, locking in the corrosion resistance.

Process & spec
Type II sulfuric anodize per MIL-A-8625; specify class and thickness on the drawing.
Film thickness
8–15 µm typical — dimensional growth ~half the film per surface, usually inside ±0.02 mm budgets.
Hardness
Substantially harder than bare aluminum; resists scratches and wipe-wear, not gouging.
Electrical behavior
Dielectric — grounding points must be masked or chem-filmed.
Appearance
Transparent satin-silver; final look tracks the surface prep (machined vs. bead blasted) and the alloy.

Benefits

Why clear anodize is the default

It solves the three failure modes of bare aluminum — corrosion, fingerprints, and handling wear — at the lowest finishing cost.

Corrosion protection

Sealed Type II film survives humidity, handling, and cleaning agents that stain bare aluminum within weeks.

Keeps the machined look

The only protective finish that preserves the metallic aluminum aesthetic engineers usually want to keep.

Scratch and wipe resistance

Hard oxide shrugs off the daily contact that polishes and mars bright bare surfaces.

Minimal dimensional impact

At 8–15 µm, most toleranced features need no compensation — confirm only on precision fits.

Stable base for marking

Laser marking on clear anodize produces crisp dark contrast for part numbers and legends.

Electrical insulation where useful

The dielectric film isolates mounting faces — an asset or a trap, depending on your grounding plan.

Typical applications

Where clear anodized parts are specified

Essentially everywhere machined aluminum meets people, humidity, or paying customers — clear anodize is the volume finish of precision machining.

Instrument and equipment housings

The standard protective finish for machined enclosures in test, measurement, and industrial equipment.

Machine and automation hardware

Brackets, plates, and guards handled with coolant-wet gloves through years of service.

Medical and lab equipment

Sealed film withstands disinfectant wipe-downs — the baseline finish for clinical hardware.

Robotics structures

Arm hardware and cell components protected without hiding their machined character.

Aerospace tooling

General protection on tools and GSE where hardcoat's thickness isn't needed.

Consumer-adjacent hardware

Bead blasted plus clear anodize — the recipe behind the 'premium aluminum' look.

Design considerations

Designing for clear anodize

Clear anodize is forgiving, but these callouts prevent the handful of surprises it can spring.

State thickness and class

Write 'Type II clear, 10–15 µm' rather than 'anodize'. Thickness drives protection, fit change, and price — make it a number.

Decide pre- or post-coat dimensions

One drawing note — 'dimensions apply after anodize' — resolves every fit question. It's usually the right answer.

Mask grounding and bonding points

The film is an insulator. EMI lands, ground pads, and bonding faces get masked bare or chem-filmed after — mark them in CAD.

Threads: coat or mask, but say which

Type II over threads slightly tightens fit; usually acceptable at 6H/6g but state your preference so gauging matches.

Plan the racking point

Every part hangs on a rack that leaves a small bare witness mark. Approve a location — inside a bore, under a label — before the first batch.

Match alloys on visible sets

Clear film shows the metal's own tone: 6061 bright, 7075 darker. Parts that sit together should share an alloy and an anodizing lot.

Compatible aluminum grades

Alloy compatibility with clear anodize

All the common grades take Type II — what changes is the color you get.

Alloy	Suitability	Engineering notes
6061-T6	Excellent	The reference: bright, uniform, repeatable silver — design cosmetic sets around it
5052-H32	Very good	Slightly warmer tone than 6061; great added protection for wet service
7075-T6	Good	Yellow-grey cast from zinc content — fine alone, mismatched next to 6061
2024-T351	Fair	Thinner, greyer film — treat as protection; use black anodize for cosmetics
MIC-6	Fair	Mottled matte result on cast structure — acceptable on tooling, not on show faces

Comparing coatings instead? Return to the aluminum surface finishes hub or read the full anodized aluminum CNC machining guide.

Quote your clear anodized parts

Upload CAD with film thickness, masked features, and the pre/post-coat dimension note. An engineer confirms fit compensation and racking before machining starts — quote within one business day.