Surface Finishing FAQ

At Boona, we offer a comprehensive range of finishes for both metal and plastic parts. Our capabilities include Anodizing, Powder Coating, Wet Painting, Electroplating, Bead Blasting, Polishing, and Laser Engraving. We treat surface finishing as a critical step in Rapid Prototyping and low-volume production to ensure your parts look and feel like final products.

 If you do not specify a finish, parts from our CNC Machining Service will have a standard “As-Machined” finish. This typically has a surface roughness of Ra 3.2μm (visible tool marks but smooth to touch). We remove sharp edges (deburring) as standard.

Ra measures the average roughness of a surface.

• Ra 3.2μm: Standard machined finish.
• Ra 1.6μm: Smooth machined finish (slower feed rate).
• Ra 0.8μm: Fine finish (ground or carefully machined).
• Ra 0.4μm: Polished/smooth (requires post-processing).
• Ra 0.05μm: Mirror Polish (Optical grade).

Most finishes add thickness to the part.

• Anodizing: Adds ~5-10μm per side.
• Powder Coating: Adds ~60-100μm per side.
• Painting: Adds ~20-50μm.
• Critical: You must tell us which dimensions are critical.

We will apply Masking (protection) or over-machine the part (make it smaller) to compensate for the coating thickness.

Yes. We use visual inspection (under controlled lighting) and Gloss Meters / Roughness Testers to ensure the finish meets your specifications. We also perform Adhesion Tests (Cross-Hatch) for painted parts.

• Type II (Standard): Decorative. Available in Clear, Black, Red, Blue, Gold, etc. Provides good corrosion resistance. Thickness: 5-15μm.
• Type III (Hard): Functional. Creates a super-hard, wear-resistant surface (harder than tool steel). Usually dark grey or black only. Thickness: 30-50μm. Recommended for Aluminum Parts used in robotics or sliding mechanisms.

Anodizing is a chemical reaction, not a paint. While we can match colors closely (e.g., “Blue”), exact Pantone matching is difficult due to alloy variations. For exact color matching, we recommend Wet Painting or Powder Coating.

Bead blasting sprays fine glass beads or sand at the part to remove tool marks, creating a uniform Matte/Satin texture. It is usually done before anodizing to give a non-reflective, premium look (like a MacBook surface). Common grades: #120 (Fine), #80 (Medium).

Alodine (Chem Film) is a chemical coating for Aluminum that provides corrosion resistance while maintaining electrical conductivity.

• Clear Alodine: Barely visible.
• Yellow Alodine: Golden color. This is essential for electronic chassis requiring grounding (EMI Shielding), often used in Sheet Metal Fabrication.

Anodizing requires the part to be electrically connected (racked) during the bath. This leaves two small contact points (clamp marks) where no coating is applied. We try to hide these in non-cosmetic areas (like screw holes).

• Powder Coating: Best for metal. Extremely durable, scratch-resistant, eco-friendly. Ideal for industrial enclosures.
• Wet Painting: Best for plastic or fine detail on metal. Allows exact Pantone/RAL color matching, high gloss, or soft-touch effects.

Yes. Soft-touch paint is applied over hard plastic (like ABS or PC) to give it a velvety, rubber-like feel. It is commonly used on consumer electronics and handheld device grips produced via Injection Molding.

• Texture Paint: We spray a special paint that dries with a bumpy texture (splatter finish). Good for low-volume prototypes to hide surface defects.
• Mold Texture (VDI/Mold-Tech): The texture is etched into the steel mold itself. Every part comes out textured. Best for mass production.

Yes. We sand the SLA/SLS parts to remove layer lines, apply a primer, and then spray paint them to a high-gloss, automotive-grade finish. They can look exactly like injection molded parts.

Yes. Paint adds 20-50μm. This can make snap-fits too tight. We recommend masking the mating surfaces or designing a larger gap to accommodate the paint.

Passivation is a chemical bath (citric or nitric acid) that removes free iron from the surface of Stainless Steel (304/316). It enhances the natural corrosion resistance of the material without changing its appearance.

Electropolishing is the “reverse” of plating. It removes material ion-by-ion, creating a microscopically smooth, ultra-clean, shiny surface. It is critical for Medical and Food Grade parts to prevent bacteria growth.

Black Oxide is a conversion coating for steel that creates a black appearance and mild corrosion resistance. It adds negligible thickness (<1μm), so it does not affect part dimensions. It is often sealed with oil.

Yes. Physical Vapor Deposition (PVD) creates an extremely hard, thin ceramic layer (often Gold, Black, or Rainbow color) on metal. It is used for high-end decorative hardware and cutting tools (TiN coating).

• Brushed: Uses abrasive belts to create a directional grain (hairline finish). Hides fingerprints.
• Polished: Uses buffing wheels to create a reflective, mirror-like surface.

Vapor Smoothing is a chemical process primarily for 3D Printed Nylon (MJF/SLS). It melts the outer surface slightly to seal the pores, making the part watertight, smooth, and glossy. It significantly improves mechanical performance.

Yes, but mainly on ABS material. We can plate ABS plastic with Chrome (Nickel-Chrome) to make it look and feel like metal (e.g., car emblems, bathroom fittings).

Silk Screening applies ink through a mesh to print logos, text, or warning labels on flat surfaces. For curved surfaces, we use Pad Printing. We need your artwork in vector format (.AI or .EPS).

Yes.

• On Metal: We can engrave deep or surface mark (annealing).
• On Plastic: We can cause a color change (charring) or remove paint (backlit buttons). Check our One-Stop Service for full assembly options involving marking.

Knurling is a mechanical process (done on a lathe) to create a diamond or straight pattern on a cylindrical part (like a knob) for better grip. This is a machining feature, not a coating.

Masking is the process of covering specific areas of a part (using tape, plugs, or custom fixtures) to prevent them from being coated/painted. Example: We mask grounding points (for conductivity) or bearing bores (to maintain tight tolerance) before powder coating.

Yes. If you don’t specify, we assume “As-Machined” (Ra 3.2). Please specify:

1. The type of finish (e.g., “Anodize Type II Black”).

2. The critical surfaces (e.g., “Polish side A only”).

3. Masking requirements (e.g., “Mask threads”).

 It varies widely.

Cheap: As-machined, Tumble Deburring.

Moderate: Anodizing, Bead Blasting, Powder Coating.

Expensive: Mirror Polishing, Hard Anodizing, Plating. Upload your file to get an Online Quote to compare costs.

Generally, No. We focus on finishing parts that we manufacture to guarantee quality. Finishing someone else’s parts carries a high risk of unknown material defects appearing during the process.

We place parts in a vibrating bowl with ceramic or plastic media. This removes sharp edges and creates a uniform, non-directional matte finish. It is the most economical way to deburr batch parts.

Yes. Heat treatment (hardening) creates a “scale” or discoloration on the surface. We usually recommend grinding or blasting after heat treatment to restore the appearance.

Yes. Raw carbon fiber can degrade under UV light. We apply a UV-resistant Clear Coat (Gloss or Matte) to protect the resin and enhance the depth of the fiber weave.

• Zinc Plating: Thin, bright coating for small machined parts/screws.
• Hot Dip Galvanizing: Thick, dull grey coating for large structural steel. Boona primarily offers Zinc Plating (Clear/Blue/Yellow) for precision parts.

Yes. We can spray the inside of plastic enclosures with Conductive Copper or Nickel paint. This blocks electromagnetic interference, protecting sensitive electronics inside.

We take packaging seriously. Finished parts are individually wrapped in foam, bubble wrap, or placed in custom blister trays to prevent scratching. If damage occurs, we will rework or replace the parts.