CNC Surface Finishes
Anodizing Type II/III, plating, passivation, black oxide, powder coat — quoted with your machining, shipped as one lot.
One PO, Finished Parts — No Finish Broker Required
The right CNC surface finish does three jobs: protects against corrosion, controls appearance, and in some cases improves wear or electrical performance. Getting it wrong — or managing a separate finishing vendor — adds weeks and quality risk. IsoCNC manages finishing as part of your machining order: parts are machined, finished through our vetted local partners, then inspected and shipped as one lot with one point of accountability.
As-Machined and Mechanical Finishes
- As-machined — the default and the cheapest. Visible tool paths; standard finish Ra 3.2 µm (125 µin), tighter on request
- Bead blast — glass-bead blasting for a uniform matte texture that hides tool marks. Our most-requested cosmetic finish on aluminum housings; standard texture unless you specify otherwise
- Brushed — directional satin grain for cosmetic panels and faceplates
- Polished — mechanical polishing from satin to mirror on metals; time-consuming, so reserve it for cosmetic surfaces
- Tumbling / vibratory finish — deburring and edge-break in bulk for small parts
As-Machined Surface Roughness Reference
| Finish Callout | Ra (µm) | Ra (µin) | Typical Use |
|---|---|---|---|
| Rough machined | 6.3 | 250 | Non-critical, hidden faces |
| Standard machined | 3.2 | 125 | Default on all IsoCNC parts |
| Fine machined | 1.6 | 63 | Mating and visible faces |
| Precision ground/lapped | 0.8–0.4 | 32–16 | Sealing, bearing, and optical surfaces |
Anodizing (Aluminum)
- Type II anodizing — sulfuric-acid anodize, clear or dyed (black, red, blue, and custom colors). Builds ~0.0002–0.001 in (5–25 µm) of corrosion- and wear-resistant oxide. The standard cosmetic and protective finish for aluminum parts
- Type III hard coat anodizing — thicker (~0.002 in / 50 µm), much harder oxide layer for wear surfaces, sliding parts, and abrasive environments. Adds measurable thickness — flag critical dimensions so we machine pre-anodize compensation
- Chem film (Alodine / chromate conversion) — thin conductive conversion coating; corrosion protection while keeping electrical conductivity, and an excellent paint primer base
Plating and Conversion Coatings
- Zinc plating — economical corrosion protection for steel, clear or yellow chromate; the default for steel hardware
- Nickel plating (electroless or electrolytic) — uniform hard, corrosion-resistant layer on steel, brass, and copper; electroless nickel plates evenly into bores and threads
- Tin plating — solderable, conductive finish for electrical parts
- Black oxide — mild corrosion protection with zero dimensional change; good for steel parts that must hold tight tolerance
- Passivation — citric or nitric acid treatment for stainless steel that removes free iron and restores the corrosion-resistant chromium oxide layer; standard for medical and food-contact parts
- Electropolishing — electrochemical micro-polish for stainless steel: smoother surface (typically improves Ra by 10–50%), brighter appearance, and better cleanability than passivation alone
Coatings and Paints
- Powder coat — durable, thick polymer coating in any RAL color; excellent for enclosures, brackets, and outdoor parts on aluminum and steel
- Wet paint / priming — for cosmetic prototypes and plastics; machined ABS parts take primer and paint directly
Choosing a Finish by Material
- Aluminum → Type II anodize for most parts; Type III for wear; chem film where conductivity or tight dimensions matter; powder coat for outdoor color
- Stainless steel → passivation as standard practice; electropolish for medical, food, or cosmetic parts; bead blast for uniform appearance
- Carbon steel → zinc or nickel plating, black oxide, or powder coat — bare steel will rust in transit, so always call out something
- Brass and copper → as-machined or nickel/tin plating; clear coat to prevent tarnish on decorative brass parts
- Plastics (Delrin, PEEK, ABS) → typically as-machined or bead blast; no plating or anodizing. See Delrin and PEEK notes
How We Control Finish Quality
Finish callouts from your drawing are captured at quote stage, masked and processed per spec, then verified before shipment: coating thickness checks on anodize and plating, visual inspection under controlled lighting, and final dimensional verification by CMM inspection where tolerances are finish-sensitive. Mixed-finish parts (e.g. anodize + masked threads) are routine — just call out the masking on your drawing.
Get Finished Parts, Quoted Together
Upload STEP files and drawings with your finish callouts — we'll quote machining and finishing together with realistic lead times, typically adding 3–7 days for most finishes. See the full range of what we cut on our materials page.
Get Finished Parts, Quoted Together
Upload STEP files and drawings with your finish callouts — we'll quote machining and finishing together with realistic lead times, typically adding 3–7 days for most finishes.
Get an Instant Quote →