Surface Finishing for Appearance and Durability

Protective and cosmetic surface treatments engineered for corrosion resistance, wear protection, electrical conductivity, and finish consistency across metals and plastics.

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15+ finishing options across CNC, 3D printing, and sheet metal parts

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Aluminum, stainless steel, carbon steel, titanium, brass, and copper alloys

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Enhanced corrosion resistance, wear resistance, insulation, and durability

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ISO 9001:2015 and RoHS/REACH compliant, with CMM and gloss/roughness testing

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Engineer reviewing surface finish design

Finished metal components ready for assembly

What Is Surface Finishing and Why Does It Matter?

Surface finishing is any post manufacturing process that modifies a part's surface for corrosion protection, wear resistance, electrical conductivity, cosmetic appearance, or regulatory compliance. Sango applies finishes in house, whether the part comes off our CNC machining, sheet metal fabrication, injection molding, or 3D printing lines.

This means your finish specification is controlled by the same team that machined or molded your part, maintaining dimensional accuracy and eliminating the handling damage that often happens during outside transport.

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Surface Roughness and Dimensional Specification Table

Representative roughness levels (Ra) and dimensional tolerances for key finishing processes.

Surface RoughnessFinishing ProcessDimensional Thickness ChangePrimary Application / Benefit

As-Machined (Standard)

Ra 1.6 – 3.2 µm0 µm Standard structural and internal mechanical components

Bead Blasting

Ra 1.6 – 3.2 µmMinimal (<2 µm) Uniform matte cosmetic finish, eliminates tool marks

Anodizing Type II

Ra 0.8 – 1.6 µm+5 to +15 µm
(half penetrates metal)Corrosion resistance, decorative color options

Anodizing Type III (Hardcoat)

Ra 0.8 – 2.0 µm+25 to +50 µm Extreme wear resistance, high hardness for heavy duty parts

Electroless Nickel Plating

Ra 0.4 – 1.2 µm+5 to +25 µm
(completely uniform)Uniform coating for complex internal cavity geometries

Passivation / Chem Film

Unchanged0 µm
(microscopic conversion layer)Corrosion resistance without changing part dimensions

Precision Polishing (SPI A-1)

Ra 0.012 – 0.05 µm-1 to -5 µm removal Mirror surface for optical reflectors and medical molds

Powder Coating

Ra 1.2 – 3.0 µm+50 to +120 µm Heavy impact protection, outdoor weather resistance, custom RAL

The Surface Finishes Sango Applies Most Often

Each finish card includes Ra value, coating thickness, compatible materials, and typical applications.

Brushed Satin Finish

Brushing creates a directional satin finish (Ra 0.4 to 0.8µm) using 120 to 400 grit belts. Available on aluminum, stainless steel, titanium, and brass. Ideal for consumer facing panels and electrical hardware.

Black Oxide Coating

Black oxide coating is a 0.5 to 1.3 micron matte black conversion coating. Provides mild corrosion resistance and improved lubricity for fasteners, gears, and steel tooling components.

Passivation Process

Passivation removes free iron from stainless steel surfaces, forming a chromium rich oxide layer. Enhances corrosion resistance without dimensional or finish changes. Ideal for medical, food grade, and chemical hardware.

Painting

Liquid paint applied by spray gun for custom colors and cosmetic top coats where powder coating is impractical. Typical dry film thickness of 25 to 75µm. Compatible with metal, steel, and most engineering plastics.

Polishing & Buffing

Mechanical or vibratory polishing progressively removes tooling marks to reach a mirror or near mirror finish (Ra down to 0.05µm). Works on aluminum, stainless steel, brass, and copper. Ideal for mold cavities, reflectors, and cosmetic parts.

Alodine / Chem Film

Chromate conversion coating (Alodine / chem film) applied to aluminum, forming a thin conductive layer with minimal dimensional change. Improves corrosion resistance while preserving electrical conductivity.

Surface Finishing Available Across Every Manufacturing Process

Whatever process produces your part, our finishing line can treat it. Select a process below to see compatible finishes and specs.

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3D Printing

±0.008 in.Precision

1 DayFast Lead Time

SLA / MJF / SLS / SLMTechnologies

Functional prototypes and complex end use parts

Industrial nylon, resin, and photopolymer powder material

Complex geometries and internal channels without tooling cost

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How Sango's Surface Finishing Process Works

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Step 1 — Automated DFM Review

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Upload your STEP, STP, STL, or IGES file. Our engineers review your part for finish compatibility, including thread protection, tight tolerance features, and masking requirements.

Step 2 — Select Finish & Confirm Quote

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Choose your finish, texture, and color. We confirm material compatibility and price before your order enters production.

Step 3 — In House Finishing

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Once your order is confirmed, your part is machined or molded and moved directly into our in house finishing line, avoiding the shipping delays and handling damage that come with outsourcing to a third party finisher.

Step 4 — Inspection & Shipment

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Every finished part is checked for coating thickness, roughness, and color match, with data available on request before it ships.

Surface Finishing Solutions for Every Industry

Our precision finishing capabilities support mission-critical applications across global industries.

AutomotiveAnodized housings, decorative interior trim, and wear-resistant hardcoat engine components.

AerospaceMil-spec anodizing (Type II & III), chem-film passivated structural brackets, and electroplated fasteners.

MedicalPassivated 316L stainless steel, electropolished surgical instruments, and bio-compatible titanium coatings.

Consumer ElectronicsPrecision brushed aluminum panels, bead-blasted satin enclosures, and custom anodized color finishes.

RoboticsHardcoat anodized arm joints, powder-coated machine frames, and nickel-plated drive components.

AutomationCorrosion-resistant black oxide, heavy-duty powder coatings, and wear-resistant electroplating.

Frequently Asked
Questions.

What makes Sango different from other finishing providers or intermediaries?

We finish parts in house, in the same facility that machined or molded them. There is no shipping to a third party finishing shop and back, which is where dimensional drift and handling damage usually happen.

How fast can your team deliver finished parts?

What surface finishes and colors are available?

Do you offer material certificates or test reports for finished parts?

Do your finishing processes comply with RoHS, REACH, or other EU standards?

What if my finished parts do not meet the required specifications?

Surface Finishing Technical Resources

Explore All Articles

Comprehensive Guide to Metal Surface Finishes

October 12, 2026 • Guide

Surface Finishing for Appearance and Durability

What Is Surface Finishing and Why Does It Matter?

Surface Roughness and Dimensional Specification Table