CNC 部品のための完全な表面仕上げガイド (2026)
正しい表面仕上げを選ぶためのエンジニアガイド：アルマイト、メッキ、研磨、PVD、ブラスト処理など — 外観、保護、コスト、適合性。
間違った表面仕上げは、それ以外は完璧な部品を台無しにします。このガイドは、JLYPT が適用するすべての一般的な仕上げ — 何をするか、コストはいくらか、どの材料で機能するか、いつ指定するか — を解説します。
Why surface finishing matters
A bare CNC-machined surface is rarely the final state of a part. The chosen finish affects three things at once:
- Appearance. Colour, gloss, texture — for consumer products this is often the dominant requirement.
- Protection. Corrosion, wear, UV, chemicals — extends part life, sometimes by 10× or more.
- Function. Electrical conductivity, thermal emissivity, biocompatibility, hardness, friction.
Anodising (aluminium parts)
Anodising electrochemically grows an aluminium-oxide layer into the part surface. It’s harder, more corrosion-resistant, takes dye well, and is integral to the part — it cannot peel like paint.
Type II (decorative)
- Layer thickness 5–25 µm.
- Excellent for colour: clear, black, blue, red, gold, etc.
- Mild abrasion resistance, good corrosion protection.
- Cosmetic standard for consumer electronics, drone frames.
Type III (hard anodising)
- Layer thickness 25–75 µm; hardness ~60 HRC.
- Very high wear and corrosion resistance.
- Limited colours (usually grey-black or natural).
- Used for hydraulic cylinders, military, industrial machinery.
See our aluminium anodising services for capacity, colours and lead times.
Electroplating and electroless plating
Plating deposits a thin metallic layer on the part — typically nickel, chrome, zinc, gold or silver. Used when you need a property the base metal lacks (corrosion, conductivity, lubricity, wear).
| Plating type | Thickness | Best for | Notes |
|---|---|---|---|
| Zinc | 5–25 µm | Cheap corrosion protection on steel | Yellow / blue / black chromate options. Outdoor: 8 µm minimum. |
| Electroless nickel (EN) | 10–50 µm | Uniform corrosion + wear coating | Conformal — ideal for complex geometry, threaded parts. |
| Hard chrome | 25–250 µm | Wear surfaces, hydraulic rods | Hexavalent variant being phased out in EU/US. |
| Decorative chrome | 0.25 µm | Cosmetic shine on plumbing/automotive | Always over a copper + nickel base. |
| Gold | 0.05–5 µm | Electrical contacts, RF connectors | Very expensive; spec only on contact area. |
| Silver | 5–25 µm | Bus bars, high-conductivity contacts | Tarnishes; needs sealing for outdoor use. |
| Tin | 5–15 µm | Solderable surfaces, food-contact (FDA) | Avoid pure-tin in cold environments (whiskers). |
PVD (Physical Vapor Deposition) coatings
PVD evaporates a metal target in a vacuum chamber and deposits a thin (1–5 µm) ceramic-like layer on the part. The result is extremely hard, low-friction and chemically inert.
| Coating | Colour | Hardness (HV) | Best for |
|---|---|---|---|
| TiN (Titanium Nitride) | Gold | 2300 | Cutting tools, dies, decorative gold finish |
| TiCN (Titanium Carbonitride) | Bronze | 3000 | Tougher tools, dies handling abrasive materials |
| TiAlN (Titanium Aluminium Nitride) | Violet/black | 3300 | High-temp cutting (e.g., milling steel dry) |
| CrN (Chromium Nitride) | Silver | 1750 | Plastic injection moulds, food-contact |
| DLC (Diamond-Like Carbon) | Black | 3000 | Wear-resistant + ultra-low friction |
| ZrN (Zirconium Nitride) | Light gold | 2800 | Watches, decorative high-end consumer |
See our PVD coating services for available colours, substrates and lead times.
Mechanical finishes
These don’t add a layer — they alter the existing surface mechanically. They’re cheap, fast and often used as a prep step before anodising or plating.
Bead blasting
Glass beads or aluminium oxide propelled at high pressure, creating a uniform matte texture. Hides minor tool marks. Common pre-treatment for anodising.
Brushing / graining
Linear scratches with a fine wire wheel, producing the “brushed steel” look common on appliances. Directional grain hides scratches.
Polishing
Multi-stage abrasive process down to 1 µm grit, producing a mirror finish. Required before chrome plating; ~Ra 0.05 µm achievable.
Tumbling / vibratory
Parts in a bin of ceramic media. Removes burrs, eases edges, leaves a soft uniform satin. Excellent for small batches and irregular geometry.
Electropolishing
Electrochemical removal of microscopic peaks, leaving a bright corrosion-resistant surface. Standard for medical-grade stainless.
Black oxide and passivation
Black oxide (carbon & tool steels)
- Chemical conversion — does not add measurable thickness.
- Mild corrosion resistance; needs oil seal.
- Cosmetic black on tools, screws, gun parts.
- Cheaper than blueing, faster than painting.
Passivation (stainless steels)
- Removes free iron from machined surfaces.
- Restores the natural chromium-oxide passive layer.
- No visible change but dramatically improves corrosion resistance.
- Required for medical and food-contact stainless parts.
Powder coating and wet painting
Both put a polymer layer on the part, but they differ in process and durability:
| Feature | Powder coating | Wet painting |
|---|---|---|
| Application | Electrostatic powder + bake at 180–200 °C | Spray gun, multiple coats, air-dry or bake |
| Thickness | 60–125 µm | 20–80 µm |
| Durability | Higher — chip and UV resistant | Moderate |
| Surface preparation | Critical (sandblast or phosphate) | Critical (degrease + primer) |
| Substrate | Heat-tolerant materials only | Most materials including plastics |
| Colour matching | Limited to powder library | Unlimited (custom mix) |
| Cost (high volume) | Lower | Higher |
Powder coating wins for industrial enclosures, outdoor furniture and automotive parts. Wet painting wins for low-volume custom colours, plastic parts, and complex multi-tone finishes.
Finish-at-a-glance comparison
| Finish | Hardness | Corrosion | Cost (relative) | Lead time |
|---|---|---|---|---|
| As-machined + deburr | Substrate | Substrate | 1× | 0 days extra |
| Bead blast | Substrate | Substrate | 1.2× | 1 day |
| Anodise Type II | High | Excellent | 1.5× | 3–5 days |
| Anodise Type III hard | Very high | Excellent | 2.5× | 5–7 days |
| Zinc plate | Soft | Good | 1.3× | 3 days |
| Electroless nickel | Hard | Excellent | 2× | 5 days |
| Hard chrome | Very hard | Good | 3× | 7 days |
| PVD (TiN/TiCN/DLC) | Extremely hard | Excellent | 4–6× | 7–14 days |
| Powder coat | Soft | Good | 1.5× | 3 days |
| Black oxide + oil | Substrate | Mild | 1.2× | 2 days |
| Passivation (stainless) | Substrate | Restored | 1.3× | 2 days |
| Electropolish | Substrate | Excellent | 1.8× | 3 days |
How to choose: a practical decision tree
Is the part aluminium and visible?
Yes → Type II anodise (decorative) or Type III (industrial). Done.
Is the part stainless and food/medical?
Passivate at minimum. Add electropolish for surgical/implant parts.
Is the part carbon steel and indoor only?
Black oxide + oil for cosmetic; zinc plate for mild outdoor exposure.
Is the part carbon steel and outdoor / aggressive?
Electroless nickel for general; powder coat for colour; hard chrome for wear.
Does the part need extreme wear or low friction?
PVD coating — TiN for tools, DLC for low-friction sliding surfaces.
Is appearance the only requirement?
Bead blast, brush or polish based on the desired look. Cheapest route.
よくあるご質問
- PVD コーティングは通常 7〜14 日。真空チャンバーを持つ専門業者に部品を送る必要があるため。硬質アルマイトと無電解ニッケルが 5〜7 日で続きます。
- はい、複数の方法で：Type II アルマイト (アルミ)、Type III ナチュラル、黒染め (鋼)、黒色粉体塗装、DLC PVD (最も深い黒、プレミアム価格)。
- メッキと粉体塗装は測定可能な厚みを追加 (5〜125 µm)。アルマイトは部品に ~50% 入り、~50% 上に成長。PVD は 1〜5 µm 追加 — 通常無視できます。
- 同一バッチ = 優れた一致。異なるバッチ = 小さな変動。色重視の作業では「単一バッチ」を指定。
- はい。一般的なスタック：ブラスト → アルマイト、ニッケル → クロム、不動態化 → 電解研磨 (医療用ステンレス)。各層がコストとリードタイムを追加します。
- はい。六価クロムは新規の自動車・電子部品で多くの地域で禁止 (RoHS、REACH)。カドミウムメッキも同様に制限。デフォルトで適合代替案を使用します。
- アルマイト、ブラスト、ブラッシング、研磨は社内。メッキ、PVD、特殊コーティングは完全なトレーサビリティを持つ認定パートナー施設で — 表面仕上げとPVD コーティングを参照。
リードタイムが最も長い仕上げは？
完全な黒色の部品は入手できますか？
仕上げは公差にどう影響しますか？
アルマイトの色はバッチ間で一致しますか？
複数の仕上げを組み合わせることはできますか？
環境規制で制限される仕上げはありますか？
JLYPT はこれらすべての仕上げを社内で行いますか？
著者について
JLYPT Engineering Team
Senior CNC Application Engineers
Our application engineering team brings 15+ years of combined experience producing precision components for aerospace, medical, robotics and industrial automation customers.
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