Plastic surface finishing and in-house painting of automotive plastic parts: gloss black, body color, matte and clearcoat finishes on bumpers, spoilers, lips, grilles and trim. Yirox runs two paint lines with a 3C2B system, clean-room booths and measured color, gloss, film thickness and adhesion, next to our own injection molding and chrome plating.
| Item | Yirox capability |
|---|---|
| Paint lines | 2 in-house lines: L1 rotary automatic line with 24 stations; L2 overhead conveyor line with 4 manual touch-up stations |
| Paint system | 3C2B (three coats, two bakes); UV clearcoat optional |
| Curing | Pre-bake 60 °C × 10 min, topcoat bake 80 °C × 30 min |
| Clean rooms | 2 spray booths at Class 100,000 (ISO 8); flash-off and oven at Class 10,000 (ISO 7) |
| Film thickness | Total 35–50 μm (base 10–15, color 12–18, clear 15–20 μm) |
| Color tolerance | ΔE*ab ≤1.0; critical parts ≤0.8 |
| Adhesion | Cross-hatch grade 0–1 |
| Other finishes | Molded-in color and texture; chrome plating in-house |
| Order size | Low MOQ on selected items; confirmed in your quote |
Surface finishing is everything done to a molded plastic part to give it its final look and protection. For automotive exterior parts that usually means one of three routes: a finish made in the mold (texture and color), a painted finish, or a plated finish such as chrome. Good plastic surface finishing covers both how the mold surface is textured and how the part is painted after molding.
The finish affects more than looks. It protects the part from sunlight and weather, hides small marks from molding, and decides whether the part matches the car body or the rest of a product range. Because the finish depends on the material and the mold, it should be chosen before tooling starts, not after.
There are many types of plastic finishes. These are the ones used most on exterior parts.
A grain or pattern is etched or machined into the mold steel and copied onto every part. Common on trim, fender flares and lower bumper parts left unpainted. Mold texture standards such as Mold-Tech style grains are often used to specify it.
The mold is polished so parts come out shiny. Used under paint or plating, or on unpainted gloss parts. SPI finish grades are often used to describe polish levels.
A deep, mirror-like black achieved with black base and clearcoat. Popular for grilles, spoilers, mirror caps and trim.
The part is painted to match the vehicle paint code or your color standard, then clearcoated.
Low-gloss paint or clearcoat for a modern look. Gloss level is measured to keep parts consistent.
A bright metal finish on plating-grade ABS. See our chrome plating on plastic page.
Buyers and engineers often describe mold finishes with industry standards. SPI (from the Plastics Industry Association) grades polished and textured finishes: A grades are high polish made with diamond compound, B grades are semi-gloss abrasive finishes, C grades are stone finishes and D grades are blasted textures. VDI 3400 is a German standard for spark-eroded (EDM) textures, numbered by roughness.
We can work to SPI, VDI or a texture you specify, and we confirm the finish and draft angle in the DFM report. A textured surface needs more draft than a polished one, because texture grips the mold steel when the part is ejected.
Many trim parts are never painted. Their look comes entirely from the mold texture and the resin color, so choosing the texture is as important as choosing a paint color.
A light, even texture that reduces glare and hides fingerprints. It needs less draft than a deep grain.
A deeper pattern often used on lower trim and fender flares. It hides scratches well but needs extra draft so parts release cleanly.
Patterns such as honeycomb or carbon-look designs machined or etched into the steel. Common on grille inserts and styling trim.
A blasted surface such as SPI-D grades. Even matte look at low cost, good for hidden or semi-visible parts.
Texture samples or texture plates help you compare before the mold is finished. Tell us the texture standard or send a reference part, and we will confirm the draft and the steel finish in DFM.
Painting plastic car parts is different from painting metal. Plastics have low surface energy, they flex and they cannot be baked at high temperature. A good process controls every stage.
Parts are cleaned to remove release agents, dust and oils. PP and TPO parts need surface treatment so paint can bond.
A first coat gives adhesion and evens out the surface. Base coat is 10–15 μm in our 3C2B system.
The color layer, 12–18 μm, is sprayed in a clean-room booth, then the part is pre-baked at 60 °C for 10 minutes.
A clear top layer, 15–20 μm, gives gloss and weather protection. UV-cured clearcoat is available on request.
The topcoat is baked at 80 °C for 30 minutes, a temperature suitable for plastic parts.
Color, gloss, film thickness and adhesion are measured, and every part is checked visually.
3C2B means three coats and two bakes. Three layers are applied (base, color and clear) with a bake after the color coat and a final bake after the clearcoat. Compared with simpler one or two coat systems, 3C2B gives better depth of color, higher gloss and stronger weather resistance, which is why it is common on visible exterior parts.
Total film thickness on our 3C2B system is 35–50 μm. Too thin and the color may be uneven or wear through; too thick and the paint can run, crack or lose adhesion. We measure it with a coating thickness gauge on every batch.
Need a paint color matched?Send your color code or sample and we will confirm the paint system and color checks.
Piano black is one of the most requested finishes for spoilers, grilles and mirror caps, and one of the most demanding. A deep black gloss works like a mirror, so it shows flaws that a matte or textured finish would hide.
The base part must be free of sink marks, flow lines and weld lines on visible faces. That starts with part and mold design: even walls, gates on hidden faces and a polished mold. In painting, dust is the main enemy, which is why our spray booths run as Class 100,000 (ISO 8) clean rooms and our flash-off and oven areas as Class 10,000 (ISO 7).
A clear topcoat of 15–20 μm then gives the depth and protection the finish needs.
After painting, piano black parts are checked under good light against the master sample and gloss is measured at 20°, the angle used for high-gloss surfaces. Packing protects the finish so it arrives without scratches.
| Defect | What it looks like | Prevention |
|---|---|---|
| Dirt and dust inclusions | Small bumps in the paint | Clean-room booths and oven, part cleaning |
| Orange peel | Wavy, textured gloss | Spray settings and film thickness control |
| Runs and sags | Paint drips on vertical faces | Film thickness within 35–50 μm total |
| Poor adhesion | Paint lifts or peels | Pretreatment for PP and TPO, cross-hatch checks |
| Color mismatch | Shade differs from standard | Spectrophotometer checks, ΔE*ab ≤1.0 |
| Thin coverage on edges | Light edges or corners | Robot paths and manual touch-up on L2 |
| Sink marks showing through | Dents visible under gloss | Even walls and packing settings in molding |
Each plastic behaves differently under paint. We choose the pretreatment and coating to suit the resin.
| Material | Paint behavior | Our approach |
|---|---|---|
| ABS | Paints easily, good adhesion | Standard pretreatment and 3C2B paint |
| PP and modified PP | Low surface energy, paint does not bond without help | Surface treatment and adhesion base coat before color |
| TPO | Flexible, low surface energy | Surface treatment and flexible-friendly coating |
| ASA | Good UV resistance | Often left in molded color; can be painted |
| PC and PC/ABS | Tough, can be sensitive to solvents | Coating chosen for compatibility |
Paint shows every flaw underneath it. These guidelines help painted parts look right first time.
| Finish | Advantages | Limitations |
|---|---|---|
| Painted | Any color, high gloss, body color match, UV protection from clearcoat | Extra process cost, needs clean surfaces |
| Molded-in color and texture | Lowest cost, no paint to chip | Limited colors, lower gloss, may fade without UV-stable resin |
| Chrome plated | Bright metal look | Needs plating-grade ABS and plating-friendly design |
Bumper covers, spoilers and side skirts are long and curved, so a consistent finish across the whole part needs good fixturing and spray paths. Large parts run on our L2 overhead conveyor line, where parts hang on fixtures and pass through spray, flash-off and oven areas. The four manual touch-up stations on L2 let painters reach recesses and edges that automatic spraying cannot cover evenly.
Because painting is in the same factory as molding, we can feed back paint problems to the molding team quickly, for example when a weld line or flow mark shows through the gloss.
Body color or black, painted on the overhead conveyor line.
Gloss black, body color or matte, including large rear spoilers.
Gloss black and body color finishes for styling kits.
Piano black, matte black or two-tone finishes.
Gloss black and body color covers.
Small visible parts on the rotary automatic line.
Material, texture and paint system agreed before tooling.
We work to your paint code, color chip or master sample.
Color, gloss, film thickness and adhesion recorded.
ISO 8 booths and ISO 7 flash-off and oven.
Molding, painting and packing in the same plant, so parts are not shipped between suppliers.
Painted faces protected for export. See packaging.
You send the color code, chip or sample, gloss level and the faces that must be class A.
We prepare paint samples and measure them against your standard with our spectrophotometer.
Sample parts are painted on the production line and checked for color, gloss and adhesion.
You approve a master sample, which becomes the reference for production.
Parts are painted on L1 or L2 with batch checks and records.
Painted parts are wrapped and packed to protect the surface.
We offer low MOQ on selected items. Exact quantities depend on the part and color and are confirmed in your quote.
Have your part and color ready?Send them with the quantity and we will quote painting with the part.
The rotary automatic line suits repeat parts in larger batches. The overhead conveyor line handles large or complex parts such as bumper covers and spoilers, with manual touch-up stations for areas a spray gun cannot reach in one pass.
| Line | Type | Details |
|---|---|---|
| L1 | Rotary automatic line | 24 stations |
| L2 | Overhead conveyor line | Includes 4 manual touch-up stations |
| Spray booths | Clean room | 2 booths, Class 100,000 (ISO 8) |
| Flash-off and oven | Clean room | Class 10,000 (ISO 7) |
| Curing | Two bakes | 60 °C × 10 min pre-bake; 80 °C × 30 min topcoat |
| Paint system | 3C2B | UV clearcoat optional |
| Layer | Film thickness |
|---|---|
| Base coat | 10–15 μm |
| Color coat | 12–18 μm |
| Clearcoat | 15–20 μm |
| Total | 35–50 μm |
| Check | Standard |
| Color difference | ΔE*ab ≤1.0; critical parts ≤0.8 |
| Adhesion (cross-hatch) | Grade 0–1 |
X-Rite Ci64 spectrophotometer, d/8° geometry, SCI and SCE, with ΔE repeatability of 0.03 or better.
BYK micro-TRI-gloss meter at 20°, 60° and 85°, repeatability ±0.2 GU.
BYK 8500 coating thickness gauge, magnetic and eddy current, 0–1,500 μm, ±(3% + 1 μm).
Cross-hatch test in-house. Outsourced adhesion tests to ISO 2409 / ASTM D3359 and pull-off to ASTM D4541 when required.
Outsourced to SGS and CTI (CNAS-accredited labs): QUV 500/1,000 h, xenon 2,500 kJ/m², humidity to ISO 6270-2.
Every part is checked for runs, dirt, orange peel and thin areas against the master sample.
See our quality inspection page for the full list of instruments and tests.
42 machines, 90–2,500 t, molded-in finishes.
Explore automotive injection molding →
Decorative chrome on plating-grade ABS.
Explore chrome plating on plastic →
Color, gloss, film and adhesion checks.
Explore CMM inspection and PPAP →
Protective packing for painted parts.
Explore private label auto parts →A color mismatch can send a painted part straight back. Our automotive plastic painting runs on in-house 3C2B lines held to ΔE*ab ≤1.0. Each program below shows how that consistency reaches your customer.
Need to paint to the car? Get primed parts, or painted kits with hardware in the box.
See auto parts supply for body shops and installers →
Building a branded line? Your color and gloss are held from batch to batch.
See the aftermarket brand program →
Gloss scuffed in transit? Show surfaces are protected for parcel shipping.
See car accessories manufacturing for e-commerce →Quality and purchasing teams on color, gloss and batch-to-batch consistency.
“What changed for us was receiving a colour plaque and the ΔE reading with each batch. Our incoming inspection stopped being an argument.”
“Gloss black parts are unforgiving. Small differences become obvious when they’re installed next to each other. We wanted more than a visual check, and the colour inspection records gave our quality team something objective to work with.”
Names and companies withheld at the customer’s request.
The main types are molded-in finishes (texture or polish made in the mold), painted finishes (gloss, matte or body color) and plated finishes such as chrome. Each suits different parts, materials and budgets.
SPI-D2 is a textured mold finish made by dry blasting the mold steel with fine oxide media. It gives a dull, even matte surface that hides small marks and fingerprints, and needs more draft than a polished surface.
Yes. PP and TPO need surface treatment and an adhesion base coat before color, because paint does not bond well to them on its own. We include this in the process.
We work to your paint code, a color chip or a master sample. Paint samples are measured with a spectrophotometer and must be within ΔE*ab 1.0, or 0.8 on critical parts.
Piano black is a deep, high-gloss black finish made with black base and clearcoat. It is used on grilles, spoilers, mirror caps and trim. It needs a sink-free surface because gloss shows every flaw.
Yes. UV clearcoat is available as an option on our 3C2B system.
Our paint lines mainly finish parts molded in our own factory, because surface quality starts in the mold. For other parts, send us details and we will tell you whether painting them is practical.
Gloss black paint uses a black color coat and clearcoat for a deep, high-gloss finish with UV protection. Black molded-in color is the resin itself; it costs less but has lower gloss and needs a UV-stable resin such as ASA for outdoor use.
Yes. Weathering tests such as QUV and xenon are done by SGS or CTI, CNAS-accredited labs, and reports are supplied with your program.
Send your part, color code or sample. We will reply with a finish recommendation and a quote.
