Coating Selection Guide

Anodize. Plating.
PVD. Powder.
Right coating, right job.

Coatings add wear resistance, corrosion protection, or cosmetic finish. Each coating has specific capabilities and costs — matching coating to application is essential for cost-effective results.

Free DFM Review Surface finishes

01 · By category

Coating categories.

Anodizing (aluminum only)

Type II / Type III

Type II (decorative): 5-25 µm thick, 200-250 HV, color available. Type III (hardcoat): 25-75 µm, 300-500 HV, wear-resistant, limited colors. Both increase corrosion resistance of aluminum.

Plating

Chrome / Nickel / Zinc

Hard chrome: wear + corrosion, 25-50 µm. Electroless nickel: uniform coating, 5-25 µm, 500+ HV. Zinc: corrosion protection for steel, sacrificial. Cadmium: aerospace spec (declining use).

PVD coatings

TiN / AlTiN / DLC

Thin (2-5 µm) dense ceramic coatings applied by vapor deposition. 2000-3000+ HV hardness. Low friction. For cutting tools, wear surfaces, premium cosmetic.

Organic coatings

Powder / E-coat / Paint

Powder coat: 50-150 µm thick, colors, decorative + corrosion. E-coat: 15-35 µm, cathodic, automotive standard. Wet paint: 10-50 µm, variable quality.

Chemical conversion

Alodine / Phosphate

Chromate conversion (Alodine): 0.5-2 µm, clear to yellow, paint prep. Phosphate: 5-25 µm, paint prep + mild corrosion resistance.

Specialty coatings

Teflon / Ceramic / Dry film

PTFE coating: low friction, release. Ceramic thermal barrier: turbine engines. Dry film lubricant: MoS2 for aerospace bearings.

02 · By application

Application → coating.

Wear resistance

• Hard chrome plating — proven, thick (25-50 µm), 60+ HRC
• Electroless nickel with PTFE — low friction + wear
• PVD TiN/AlTiN/CrN — cutting tools, 2000+ HV, thin
• DLC (Diamond-Like Carbon) — ultra-low friction, 3000+ HV
• Hardcoat anodize Type III — aluminum parts, 500 HV
• Thermal spray — thick (100-500 µm), for severe wear

Corrosion protection

• Zinc plating — steel sacrificial protection, 5-25 µm
• Galvanizing — steel immersion in molten zinc, thick
• Powder coat — polymer barrier + UV stability
• Electroless nickel — uniform coverage, chemical resistance
• Anodize Type II — aluminum corrosion + decorative
• Chromate conversion — paint prep + mild barrier

Cosmetic appearance

• Anodize Type II — aluminum color options, durable
• Powder coat — wide color range, textured options
• PVD — premium gold, rose gold, dark finishes
• Polishing + clear coat — mirror finish preservation
• Chrome plating — bright metallic appearance
• E-coat — automotive undercoat black

Electrical

• Silver plating — lowest electrical resistance, contacts
• Gold plating — corrosion + conductivity, connectors
• Tin plating — solderable surface, economical
• Anodize Type III — insulating aluminum surface
• Conductive anodize — preserves surface conductivity
• Nickel plating — EMI shielding substrate

03 · Thickness guidance

Coating thickness by type.

Coating	Typical thickness	Growth / part tolerance	Life estimate
Anodize Type II	5-25 µm	Half grows out, half grows in	10-20 years
Anodize Type III	25-75 µm	Significant dimensional change	20+ years
Hard chrome	25-50 µm	All growth outward	10-20 years wear
Electroless nickel	5-25 µm	Uniform outward	10 years + corrosion
Zinc plating	5-25 µm	Outward	2-5 years outdoor
PVD TiN	2-5 µm	Negligible	Cutting tool dependent
DLC	1-5 µm	Negligible	Application dependent
Powder coat	50-150 µm	Outward	10-20 years outdoor
E-coat	15-35 µm	Outward	Automotive 10+ year
Chromate	0.5-2 µm	Negligible	Primer only, not standalone

04 · DFM for coatings

Design considerations.

Masking: Most coatings go everywhere unless masked. For internal threads, bearing bores, electrical contact surfaces that must not be coated, masking is required — added cost and potential for masking errors. Design: allow for masking access, consider tolerance implications if masking line isn't perfect.

Dimensional growth: Coatings add thickness. Anodize Type III adds 25-50 µm per surface — tight tolerance bores may go out of spec. For anodized parts, account for growth in dimensional tolerance. Sometimes masking is preferred over dimensional accommodation.

Drain holes: For plating and anodizing, parts are immersed — need drain holes to remove solution from interior cavities. Lack of drain holes causes: trapped plating solution, corrosion from retained chemistry, uneven coating due to air pockets. Specify drain holes in all interior cavities before sending for coating.

Electrical contact: For plating and anodizing, electrical contact required with the part. Hanging points or contact marks show on finished surface. For cosmetic parts, specify contact location (in non-visible area) or design with non-critical hanging points.

Hydrogen embrittlement: High-strength steel (60+ HRC) plating: hydrogen absorbs into metal during plating, causes delayed brittle fracture. Bake-out post-plating (at 190°C for 8-24 hours) drives hydrogen back out. Required for aerospace plating. Specify bake-out for hardened steel plating.

FAQ

Anodize Type II vs Type III — when each?

Type II: decorative, thinner (5-25 µm), wider color range, lower cost. Good for: consumer electronics, architectural aluminum, general aluminum. Type III (hardcoat): functional, thicker (25-75 µm), limited colors (black, dark gray, bronze), higher cost. Good for: firearms, military, wear surfaces, premium consumer. For aluminum housings, Type II usually adequate. For wear-prone aluminum surfaces, Type III worth the premium.

Plating selection for steel?

Zinc: cheapest, sacrificial, 5-10 year outdoor protection. Cadmium: aerospace historical (declining due to toxicity), high corrosion resistance. Nickel: electroless for uniform coverage, chemical resistance. Chrome: wear + corrosion, thickness range 25-50 µm, most durable. For new designs, avoid cadmium. Zinc for economic, chrome for wear-critical.

PVD coating economics?

PVD coatings: $20-200 per part depending on coating type and size. Premium over bare material 50-500%. Justified for: cutting tools (2-5× life), wear components (longer service), premium consumer products (aesthetic value), medical implants (biocompatibility). Not economical for: general industrial parts, parts where wear isn't primary failure mode, cost-sensitive applications.

Powder coat vs wet paint?

Powder coat: no VOC (environmental), uniform coverage including corners, durable finish, wide color range, limited to items that can handle 180°C curing. Wet paint: can be applied to heat-sensitive substrates, faster for small batches, wider color and effect range, less durable. For most industrial applications, powder coat preferred. For specialty or small-batch work, wet paint still viable.

Can I mix coatings?

Yes, sometimes. Common combinations: (1) Electroless nickel + hard chrome — nickel for corrosion, chrome for wear. (2) Zinc plating + powder coat — zinc for galvanic protection, powder for UV and appearance. (3) Anodize + PTFE impregnation — anodize for wear, PTFE for low friction. Each combination has specific processing requirements. Specify coating sequence carefully.

Lead times for coating?

Anodize: 3-5 days. Zinc plating: 2-3 days. Hard chrome: 5-7 days. Powder coat: 2-4 days. PVD: 5-10 days (specialty process). Heat treatment + coating (like stainless passivation): 7-10 days total. For tight schedules, these add significantly to delivery. Plan coatings into project timeline early.