// FINISHING — ANODIZING
Anodizing Type II & III
Electrochemical surface conversion for aluminum — corrosion resistance, increased hardness, and a consistent finish in clear or black, with post-anodize Teflon/PTFE available.
Anodizing converts the surface of aluminum into a hard, integral oxide layer that is part of the metal itself, not a coating on top of it. The result is a surface that resists corrosion, accepts dye for consistent color, and adds meaningful hardness without building up significant thickness on critical features. Rigid Concepts coordinates anodizing through our trusted finishing partner NorTex Metal Finishing so your machined parts arrive complete and ready to assemble.
Type II vs. Type III anodizing
Type II (sulfuric acid anodize) is the standard architectural and commercial process, producing a thinner oxide layer that accepts dye and paint well. It is the right choice when color consistency, paint adhesion, or moderate corrosion protection is the goal. Type III (hard anodize) is thicker, denser, and significantly harder — built for parts that face abrasion, wear, or aggressive environments. Both processes are available in clear (natural aluminum gray) and black.
- Type II — commercial anodize, excellent color and paint-adhesion properties
- Type III — hard anodize, exceptional abrasion and wear resistance
- Clear (natural) and black color options
- Post-anodize Teflon / PTFE impregnation for added lubricity and corrosion resistance
Material and size capability
Anodizing is an aluminum-only process. The oxide is grown from the aluminum itself, so the alloy and heat treatment affect the result — 6061 and 7075 both anodize reliably, and we can discuss expectations for less common alloys. Our partner NorTex can handle parts up to 84" × 20", accommodating the large structural components common in aerospace and defense work.
| Process types | Type II (commercial) · Type III (hard anodize) |
|---|---|
| Colors | Clear (natural) · Black |
| Post-treatment | Teflon / PTFE impregnation available |
| Max part size | 84" × 20" |
| Substrate | Aluminum alloys |
| Standard | MIL-A-8625 |
When to anodize
Anodizing is the default finishing call for aluminum parts that live in corrosive environments, see repeated handling, or need a dimensionally stable color. Because the oxide layer grows into the surface rather than building up on it, the dimensional impact is predictable — roughly 0.0001" per side for Type II and up to 0.001" per side for Type III — making it compatible with tight-tolerance bores and mating surfaces when pre-anodize dimensions are planned correctly.
Parts that need lubricity on top of corrosion resistance (sliding mechanisms, threaded interfaces) benefit from post-anodize PTFE impregnation, which fills the oxide’s porous structure and reduces friction without adding measurable thickness.
Anodizing pairs naturally with our aluminum CNC machining. For aluminum parts that also serve as electrical grounds or need paint adhesion without a hard oxide, see our chem film / chemical conversion coating page.
// FAQ
Frequently asked questions
Type II (sulfuric anodize) produces a thinner, more ductile oxide layer suited for color, paint prep, and moderate corrosion protection. Type III (hard anodize) is thicker and much denser, offering significantly higher surface hardness and wear resistance. Type III is the right call for parts exposed to abrasion or aggressive environments.
Yes, but predictably. Type II adds roughly 0.0001" per side; Type III adds up to 0.001" per side. When tight-tolerance bores or mating features need to be held after anodize, we factor this in at the machining stage — send us the drawing and we’ll coordinate.
Our standard colors through NorTex are clear and black. Other dye colors may be available — contact us to discuss your requirement.
PTFE impregnation seals the porous anodize oxide layer, reducing friction and improving corrosion resistance. It is a good choice for sliding surfaces, threaded fasteners, and assemblies where lubricity matters. It does not add meaningful thickness to the part.
MIL-A-8625, the standard military specification for anodic coatings on aluminum and aluminum alloys. Type I, II, and III call-outs in the spec map to the commercial processes we offer.
Send us the hard one.
Upload your drawing or STEP file and we'll come back with pricing and lead time — from a single high-mix part to full production runs, held to exacting tolerances.