Type II sulfuric anodizing
Common for corrosion protection and decorative clear or dyed finishes. Quote the required appearance together with alloy, visible surfaces, masking, sealing, and sample approval.
Engineering color reference
Aluminum Anodizing Color Chart
Compare common Type II and Type III appearances, then define the alloy, visible surfaces, sample approval, masking, and inspection method that make a color requirement quotable.
Sample approval matters more than a screen color
Short answer: an online color chart is a planning aid, not a color guarantee. Aluminum alloy, temper, machined texture, pretreatment, coating thickness, dye bath, sealing, rack position, lighting, and batch conditions can all change the visible result. For cosmetic work, approve a physical coupon and record the viewing or measurement method before production.
Color planning table
Common aluminum anodizing appearances
Availability and repeatability depend on the approved supplier route. The swatches below are labels only; they are not digital acceptance standards.
| Appearance | Typical route | Engineering notes | Approval focus |
|---|---|---|---|
| Clear / natural | Type II clear | Alloy and pretreatment can shift the finish from bright silver to a muted natural tone. | Alloy, texture, gloss, visible surfaces |
| Black | Type II dyed or Type III dark finish | Deep black and uniformity depend on alloy, coating, dye, sealing, and geometry. | Physical coupon, lighting, rack marks |
| Red | Type II dyed | Decorative red can vary between orange-red, neutral red, and darker shades. | Approved range, fading and batch boundary |
| Blue | Type II dyed | Machined texture and coating thickness influence brightness and saturation. | Gloss, texture and sample comparison |
| Gold | Type II dyed | Gold labels cover a wide range from pale champagne to deep yellow-brown. | Physical master sample, alloy consistency |
| Green | Type II dyed | Dye availability and achievable shade are supplier-specific. | Sample availability and acceptance range |
| Gray / bronze / olive | Type III natural | Natural hard-anodize color is driven by alloy and process, not selected like a paint code. | Functional coating first, appearance boundary second |
Type II vs. Type III: decide by function first
Type III hard anodizing
Selected when wear-oriented coating performance is more important. Natural color often trends gray, bronze, olive, or dark; dimensional buildup and post-machining strategy must be reviewed.
What changes the final color?
Alloy and temper
Different aluminum chemistries respond differently. Keep alloy and temper consistent between sample and production.
Machined texture
Tool paths, blasting, brushing, polishing, and chemical pretreatment change reflectivity and perceived color.
Coating and dye
Coating thickness, dye route, bath control, and sealing influence saturation and uniformity.
Geometry and racking
Recesses, edges, threaded areas, electrical contact, and rack marks need drawing-level planning.
Lighting and measurement
Agree whether acceptance is visual, based on a master coupon, or uses an agreed color-measurement method.
Batch control
Define whether different lots may be mixed in one assembly and how replacement parts will be approved.
RFQ checklist
Make the finish requirement quotable
- 1. Alloy, temper, CAD, drawing, quantity, and delivery country.
- 2. Type II or Type III objective and functional coating requirement.
- 3. Visible surfaces, target color, texture, gloss, masking, and rack-mark zones.
- 4. Physical master, sample coupon, viewing condition, or agreed measurement method.
- 5. Inspection documents, protective packaging, and batch-matching requirement.
Related engineering evidence
Aluminum anodizing FAQ
Can this chart guarantee the final anodized color?
No. Use it to scope options, then approve a physical sample and acceptance method for cosmetic parts.
Can Type III hard anodize match a decorative color?
Type III is selected primarily for coating performance. Its natural color depends on alloy and process, so decorative matching must be evaluated separately.
What should be marked on the drawing?
Mark visible surfaces, masked zones, threaded or fitted features, rack-mark limits, coating type, and any sample or inspection requirement.