Surface Finishing
Surface finishing covers anodizing, powder coating, plating, polishing, painting, and passivation applied after machining, forming, or molding to protect against corrosion, hide tool marks, match color specs, or improve wear resistance. Coating thickness ranges from 0.25μm (chrome plating) to 100μm (powder coating), and affects every dimension on the part, masking and post-finish machining are part of the design, not afterthoughts. For material compatibility, see our Materials & Properties guide.
Surface Finishing Capabilities
| Feature | Description |
| Maximum Part Size | Anodizing tank: 3000×1500×800mm／Powder coat oven: 4000×2000×1500mm／ Plating tank: 2000×1000×800mm |
| Coating Thickness | Anodizing Type II: 5–25μm／Type III: 25–75μm／Powder coat: 60–100μm／Zinc plating: 5–15μm／Chrome plating: 0.25–2.5μm |
| Surface Roughness | Mirror polish: Ra 0.05–0.1μm／Brushed: Ra 0.4–0.8μm／Bead blast: Ra 1.6–3.2μm |
| Corrosion Resistance | Anodized aluminum: 336+ hours／Zinc-plated steel: 96–240 hours／ Powder coat on phosphated steel: 500+ hours |
| Standard Lead Time | Standard finishes: 3–7 business days／Multi-step finishes: 7–14 days |
| Processes | Anodizing, Powder Coating, Plating, Bead Blasting, Brushing, Polishing, Painting, Passivation |
Materials Supported
Common Metal Materials
Aluminum takes the widest range of surface finishes. Anodizing is the most common: Type II for color and basic corrosion resistance, Type III (hard anodize) for wear surfaces. Powder coating, painting, and polishing also work. 6061 and 6063 anodize evenly; 7075 contains higher zinc and tends to show grain patterns through the anodize layer.
Stainless steel finishes are about surface texture, not corrosion protection, the metal handles corrosion on its own. Brushed (#4 finish), bead blasted, mirror polished (#8 finish), and passivated are the standard options. Electropolishing for medical and food-grade parts where bacterial adhesion matters.
Carbon steel rusts without surface protection. Powder coating (60–100μm thickness) and zinc plating are the defaults for structural parts. Black oxide adds a thin corrosion barrier on tools and fasteners without changing dimensions. E-coating (electrodeposition) covers complex geometries evenly where spray painting can’t reach
Brass surfaces patinate over time without protection. Lacquering preserves the original gold color; antique-style chemical patina darkens it intentionally. Polishing to mirror finish is common on decorative parts. Brass doesn’t accept anodizing or powder coating well, paint and lacquer are the working options
Copper patinates faster than brass. Clear lacquer locks in the bright finish; chemical patina (statuary bronze, verdigris) for decorative applications. Tin plating and silver plating for electrical contacts where the underlying copper would oxidize and lose conductivity. Polishing brings copper to a mirror state but the finish dulls within weeks without protection
Common Plastic Materials
POM has a waxy surface that resists paint adhesion. Surface treatment (flame, plasma, or chemical etch) is needed before painting. Pad printing works after surface activation. POM doesn’t accept most coatings without pre-treatment, design for in-resin color when possible instead of post-paint finishing
Nylon dyes well, heated dye bath penetrates 0.5mm deep, color goes through the surface layer instead of sitting on top. Painting works after primer; sanding before primer improves adhesion. Nylon’s moisture absorption causes dimensional shifts that affect paint thickness consistency,condition parts before finishing
ABS is the easiest plastic for surface finishing. Takes paint, primer, vapor smoothing (acetone), and plating well. Chrome plating on ABS is the standard process for automotive trim and decorative parts. Pad printing, hot stamping, and laser marking all work directly on ABS without pre-treatment
PC scratches easily, protective hard coatings extend service life on optical and display parts. Paint adheres directly without primer in most cases. Avoid solvent-based finishes on stressed areas; PC cracks under solvent attack on bent or molded-in stress zones. Anti-fog and anti-reflective coatings are common on PC lens components
Finish Selection Guidance
Pick the finish based on what the part needs to survive. Anodized aluminum holds up outdoors for 5–10 years. Powder-coated steel handles abrasion better than wet paint but adds 60-100μm to every dimension. Brushed stainless hides fingerprints; mirror-polished stainless shows every fingerprint. Plating adds corrosion resistance plus conductivity for electrical parts. Order matters. Surface finish always comes after machining, forming, and welding, never before. Heat-affected zones from welding burn off most coatings. Threaded holes and bearing surfaces get masked before finishing, or machined again after. Call out which features get protected on the drawing.
Specifications & Standards
Surface finish specifications cover thickness, color, gloss, and durability. Coating thickness affects every dimension, anodizing adds 5–25μm per surface, powder coating adds 60–100μm, plating varies 5–50μm depending on type. Tight-tolerance features need to be masked or machined after coating.
| Coating Thickness | Anodizing Type II: 5–25μm Type III: 25–75μm Powder coat: 60–100μm Zinc plating: 5–15μm Chrome plating: 0.25–2.5μm |
| Color Standards | RAL, Pantone, NCS, or custom color match. Anodizing limited to standard dye colors; powder coat covers full RAL range. Color consistency batch-to-batch held to ΔE ≤ 2 |
| Gloss Levels | Matte (5–10 GU), Satin (20–40 GU), Semi-gloss (50–70 GU), High gloss (85+ GU). Measured at 60° per ASTM D523 |
| Surface Roughness | Mirror polish: Ra 0.05–0.1μm Brushed: Ra 0.4–0.8μm Bead blast: Ra 1.6–3.2μm As-machined: Ra 1.6–3.2μm typical (up to Ra 6.3μm on deep pockets, long-reach features, and turned surfaces) |
| Adhesion Standards | Cross-hatch test per ASTM D3359, minimum 4B rating. Pull-off adhesion per ASTM D4541 for structural coatings |
| Corrosion Resistance | Salt spray test per ASTM B117. Anodized aluminum: 336+ hours / Zinc-plated steel: 96–240 hours / Powder coat on phosphated steel: 500+ hours |
| Maximum Part Size | Anodizing tank: 3000×1500×800mm Powder coat oven: 4000×2000×1500mm Plating tank: 2000×1000×800mm |
| Lead Time | Standard finishes: 3–7 business days. Multi-step finishes (e.g., polish + plate): 7–14 days |
Surface Finishing Options
Anodizing
Electrochemical process for aluminum. Type II builds 5–25μm color layer in dyed bath. Type III hard anodize builds 25–75μm wear-resistant layer. Standard colors: black, clear, red, blue, gold. Type III stays natural gray or black
Powder Coating
Dry powder applied electrostatically, then cured at 180–200°C. Builds 60–100μm thickness. Full RAL color range, matte to high-gloss finish options. Standard finish on steel parts going outdoors or into abrasive environments.
Plating
Zinc plating for low cost corrosion protection on steel parts, often followed by yellow or clear chromate seal. Nickel plating for harder, more decorative surfaces. Chrome plating for wear surfaces and bright cosmetic finishes.
Bead Blasting
Glass bead or aluminum oxide media blasted at the surface under pressure. Creates uniform matte texture, hides machining marks. Standard pre-treatment before painting or anodizing, the rough surface improves coating adhesion.
Brushing
Abrasive belt or wheel drawn across the surface in one direction. Creates linear grain pattern. Common on stainless steel panels, aluminum trim, and decorative parts. Grit 120–240 produces #4 architectural finish
Polishing
Progressive grit sanding (240 → 400 → 800 → 1500 → 3000) followed by polishing compound on a buffing wheel. Mirror finish (#8) reflects clearly. Time-intensive, labor cost scales with surface area and finish target.
Painting
Liquid paint applied by spray gun, air-dried or oven-cured. Lower thickness than powder coat (typically 30–60μm). Covers complex geometries and small batch runs more economically than powder.
Passivation
Chemical process for stainless steel that removes free iron from the surface. Improves corrosion resistance without changing appearance or adding measurable thickness. Required on medical parts.
Design Guidelines
A part can be coated technically and still come back with runs, masking errors, or color mismatch. Design for finishing means knowing how the coating builds on edges, how masking lines fall, and how the finish thickness affects mating features before the part goes to the finishing line
| Core DFM Principles | Better design for finishing means: – masking specified on the drawing for critical features – mounting points identified for hanging in plating/coating tanks – dimensions account for coating buildup on tight tolerances – edges broken to prevent thin coating on sharp corners – material and finish compatible (e.g., not specifying powder coat on heat-sensitive substrates) |
| Edge Treatment | Sharp edges hold less coating than flat surfaces, 80% buildup on sharp corners vs 100% on flat faces. Specify edge break (0.3–0.5mm chamfer) for parts going through corrosive environments |
| Masking Areas | Threaded holes, bearing surfaces, electrical contacts, and grounding points need to be masked. Call out masking on the drawing with notes or separate detail views. Plug masking on threads adds cost per part |
| Coating Buildup | Anodizing adds 5–25μm per surface (10–50μm on enclosed features). Powder coat adds 60–100μm. Plating varies. Mating features with H7/g6 fits need post-finish reaming or pre-undersizing |
| Color and Batch Consistency | Anodizing color varies batch-to-batch,parts from different runs may not match exactly. Critical color-matched assemblies run together in one batch. Specify ΔE tolerance on the drawing if matching matters |
| Avoid Unnecessary Finish | Internal surfaces, hidden faces, and non-functional areas don’t need full cosmetic finishing. Specify which surfaces need full finish, which need basic protection, and which can stay bare to control cost. |
Typical Applications
Concept Models
Early visual and tactile models that lock in form, proportion, and styling before any tooling is committed.
Functional Prototypes
Working parts in production-intent materials, built to verify fit, function, and mechanical performance under real loads.
Engineering Validation
Rigorous testing of strength, durability, and environmental resistance to confirm the design meets performance and safety targets.
Fit & assembly testing
Dimensional and mating checks across components to verify tolerances, clearances, and assembly before scale-up.
Market testing samples
Near-final, cosmetically finished units in small batches for customer, retailer, and certification feedback.
Bridge production
Limited pre-mass runs on near-final tooling that keep you shipping while hard tooling and full production ramp up.
Equipment & Capacity
Surface finishing capacity comes down to tank size, oven dimensions, and line throughput. Anodizing and plating run in tanks; powder coating runs through ovens; painting can be done in booths or automated lines. Mixing finishes on one part (e.g., zinc plate plus powder coat) means routing the part through multiple lines and adds setup time per step
Quality Control Flow
Incoming inspection
Bare parts checked for substrate condition before finishing starts, pre-existing scratches, burrs, weld discoloration, and oil residue all transfer through anodizing and show under powder coat. Aluminum parts checked for alloy grade (6061 anodizes evenly, 7075 shows grain pattern). Stainless verified for grade passivation works on 304/316 but not on 303 free-machining grade. Masking instructions cross-checked against the drawing before parts hit the line.
In-process inspection
First-article check on the first part off each finishing batch, color match against approved sample, coating thickness with eddy current gauge, coverage on edges and recessed features. Anodizing tank chemistry monitored every shift (sulfuric acid concentration, temperature, current density). Powder coat oven temperature logged at 180–200°C; under-cure causes adhesion failure visible only after weeks in service.
Final inspection
Coating thickness verified at multiple points (anodizing 5–25μm Type II, 25–75μm Type III; powder coat 60–100μm; zinc plating 5–15μm). Adhesion tested with cross-hatch tape pull per ASTM D3359, minimum 4B rating. Color matched to RAL or Pantone reference under controlled D65 lighting; ΔE ≤ 2 on critical batches. Visual inspection for runs, drips, orange peel, blistering, and masking errors on threads and bearing surfaces.
Documentation and traceability
Substrate material records, finishing line parameters, batch numbers, and inspection data archived per lot. Parts trace back to specific anodizing tank run, powder batch, or plating line cycle. Salt spray test reports per ASTM B117 available on request, anodized aluminum 336+ hours, zinc-plated steel 96–240 hours, powder coat on phosphated steel 500+ hours. RoHS and REACH compliance documentation included for parts shipping to EU markets.
Related Solutions
Rapid Prototyping
Low Volume Production
Production Tooling
End-to-End Manufacturing
Surface Finishing: Common Questions
Which surface finishes do you offer?
Anodizing (Type II and Type III hard anodize for aluminum), powder coating (full RAL range, steel and aluminum), zinc plating, nickel plating, chrome plating, bead blasting, brushing, polishing (up to mirror #8 finish), spray painting, passivation (stainless steel), e-coat, and black oxide. Specific finishes depend on material. Include the part material and finish requirement in the RFQ and we will confirm compatibility.
Does surface finishing change part dimensions?
Yes. Every coating adds thickness to the part surface. Anodizing Type II adds 5 to 25μm per surface. Type III hard anodize adds 25 to 75μm. Powder coating adds 60 to 100μm. Zinc plating adds 5 to 15μm. Chrome plating adds 0.25 to 2.5μm for decorative chrome, up to 25μm for hard industrial chrome. Mating features with tight fits (H7/g6 and similar) need to be pre-undersized before finishing or reamed after. Call out which features are critical on the drawing.
Which finishes are available for aluminum?
Anodizing (Type II in black, clear, red, blue, gold; Type III in natural gray or black), powder coating, bead blast, brushing, polishing, and spray paint. 6061 and 6063 anodize evenly. 7075 contains higher zinc content and tends to show grain patterns through the anodize layer; confirm finish expectations before ordering on 7075. Hard anodize (Type III) is standard for wear surfaces, sliding contacts, and hydraulic components.
Which finishes are available for steel?
Carbon steel and cold-rolled steel: powder coating (60 to 100μm, full RAL range), zinc plating (often followed by yellow or clear chromate seal), e-coat, black oxide, and spray paint. Stainless steel: brushed (#4 finish), bead blast, mirror polish (#8 finish), passivation, and electropolishing for medical or food-grade parts. Stainless does not require corrosion protection coatings; finishing is about surface texture and cleanliness.
How do I specify color for powder coating or painting?
Provide a RAL number, Pantone reference, or NCS code in the drawing or RFQ. Powder coat covers the full RAL range at any gloss level from matte (5 to 10 GU) to high gloss (85+ GU). Color consistency batch-to-batch is held to ΔE 2 or better. For anodizing, color options are limited to standard dye colors; custom color match on anodized parts is not available. If you need a physical color chip approved before production, request a pre-production sample in the RFQ.
Which areas need masking, and how do I specify them?
Threaded holes, bearing surfaces, electrical contacts, grounding points, and any feature with a tight dimensional tolerance need masking before finishing. Mark masking areas on the drawing with notes or separate detail views. Plug masking on threaded holes adds cost per part; group masked features on one side of the part where possible to reduce setup. Features not called out on the drawing are assumed to receive full finish coverage.
What is the lead time for surface finishing?
Standard single-step finishes (bead blast, Type II anodize, powder coat, zinc plate) run 3 to 7 business days after parts are received. Multi-step finishes such as polish plus plate, or bead blast plus hard anodize plus paint, run 7 to 14 days. Passivation on stainless runs 1 to 3 days. Lead time includes pre-treatment, coating, inspection, and packing. Rush options are available on request for single-step finishes.
Can you finish parts made by another supplier?
Yes. Send the parts with a drawing that specifies the finish, masking requirements, color reference, and any applicable standard (ASTM B117 salt spray hours, MIL-A-8625 for anodize, etc.). We inspect parts on arrival for surface defects before finishing. Scratches, weld spatter, or tool marks present before coating will show through or under most finishes; incoming part condition affects the final result.
Do you sign NDAs before reviewing part files?
Yes. Send an NDA request to [email protected] before uploading files. We return a signed copy within 24 hours on business days. Files can also be uploaded through our secure RFQ portal.
What corrosion resistance can I expect from different finishes?
Per ASTM B117 salt spray test: anodized aluminum holds 336 hours or more. Zinc-plated steel runs 96 to 240 hours depending on chromate seal type. Powder-coated steel on phosphated substrate runs 500 hours or more. Hard chrome on steel varies by base metal preparation. Passivated stainless does not have a salt spray rating in the same sense; it removes free iron that would cause tea staining and surface rust. If your part has a specific corrosion resistance requirement, include the test standard and hours in the RFQ.
Ready to Finish Your Parts?
Include your finish spec in the RFQ and get a quote within 12 hours. Standard finishes in 3 to 7 business days.
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