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UV-Cured Coating

Coatings for plastics · Spray applied

UV-cured coating is a clear or pigmented liquid film polymerized rapidly by ultraviolet light.

Injection molding3D printingStandard cost $$Insulating
Quote a part with UV coatingCompare coatings for plastics
UV-Cured Coating on a machined part

What is UV coating?

It is used on plastic housings and lenses for gloss, scratch resistance, stain resistance, and rapid production cure.

How it works

A formulated liquid containing oligomers, reactive diluents, additives, and photoinitiator is sprayed or flowed onto a clean plastic surface. Ultraviolet energy activates the photoinitiator and crosslinks exposed film within seconds. Lamp spectrum, dose, distance, oxygen inhibition, pigment, and part geometry control cure. Deep undercuts and shadowed faces may remain undercured unless the process uses multiple lamps, part rotation, or a dual-cure chemistry.

Why specify it

  • Typical plastic topcoat is 10–30 µm
  • Cures in seconds under the qualified UV dose
  • Can improve scratch and stain resistance
  • Provides clear high-gloss or controlled matte appearance

Where it falls short

  • Shadowed geometry may remain undercured
  • Some resins stress-crack under coating solvent or cure shrinkage
  • A hard film can craze on flexible parts
  • Outdoor yellowing depends on the exact resin and stabilizer package

UV coating at a glance

UV coating is strongest on cosmetic quality (90 of 100), at a standard cost. Surface hardness is not rated: the finish leaves the part's own surface.

Corrosion protectionLow25 / 100
Surface hardnessNot rated—
Cosmetic qualityExcellent90 / 100
LubricityLow20 / 100
Relative costStandard35 / 100
CorrosionHardnessCosmeticLubricityEconomy

Each score is 0–100 against every finish in this catalog. Corrosion comes from salt-spray life (ASTM B117, log scale) and hardness from the finish layer's Vickers or pencil hardness; cosmetic, lubricity and cost are FabDigit's engineering assessment. Economy on the radar is the inverse of cost.

UV coating key numbers

Typical values from the governing specifications and shop practice; bars are this finish against the highest value among coatings for plastics finishes.

Thickness10–30 µm0.39–1.2 mil
Thickness
10–30 µm on molded or printed polymer
Electrical
Insulating
Colours
  • clear
  • custom tint
  • custom color
Appearance
Usually clear and high gloss, with matte grades available; substrate defects remain visible.

Specifications for UV coating

The documents a drawing cites to define this finish, with the Type / Class rows that apply. Each links to a page explaining the standard.

Drawing call-out

CLEAR UV-CURED ACRYLATE TOPCOAT, 15–25 µm DFT, 85–95 GU AT 60°; FULL CURE ON ALL VISIBLE SURFACES; MASK SNAP HOOKS AND BOND AREAS

Which materials take UV coating?

Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library.

Material familyVerdictNotes
Aluminum
YesCommon over conversion coating, anodize, or primer.
MJF
YesCommon clear or tinted topcoat after blast and seal.
Polymer
YesResin, stress state, and surface energy require qualification.
  • PC and ABS systems need stress-crack testing
  • PP and PE generally require activation
SLS
YesCommon clear or tinted topcoat after blast and seal.
Steel
YesCommon over phosphate, primer, or cleaned bare steel.
Brass
With careClean tarnish and qualify adhesion.
Composite
With careSeal porosity and verify matrix compatibility.
Copper Alloy
With careClean tarnish and qualify adhesion; some solvents stain copper.
FDM
With careShadowed layer valleys can remain undercured; seal and orient for lamp access.
Magnesium Alloy
With careNeeds conversion coating or primer before an organic film.
SLA
With careFully post-cure and verify adhesion to the resin.
Stainless Steel
With careNeeds mechanical or chemical activation for adhesion.
Titanium
With careNeeds activation or primer for organic films.
Zinc Alloy
With careNeeds conversion coating or primer; some solvents attack zinc.
DMLS / SLM
LimitedOnly as an appearance film; metal AM usually uses metal finishes.

How UV coating is applied, and what it does to the part

  1. 1Clean
  2. 2Activate or prime if required
  3. 3Mask
  4. 4Apply coating
  5. 5Flash if required
  6. 6Expose to qualified UV dose
  7. 7Post-cure if specified
  8. 8Inspect cure, gloss, and adhesion
DimensionsAllow 10–30 µm per coated face and avoid coating snap hooks or tight sliding fits without validation.
Build-up per side10–30 µm — Adds its cured dry-film thickness to exposed faces.
MaskingUsually needed. Mask threads, snaps, optical zones not included in the qualification, adhesive areas, and contacts.
ElectricalInsulating
AppearanceUsually clear and high gloss, with matte grades available; substrate defects remain visible.
Added lead time2–5 working days on top of the bare part

Design rules for UV coating

What to decide on the drawing before the part goes to the finisher.

  1. Give every coated face direct lamp exposure.UV cannot cure a coating hidden in a geometric shadow.
  2. Qualify solvent stress cracking on the molded resin.PC, ABS blends, and residual molding stress can craze.
  3. Specify UV dose and lamp spectrum in the process plan.Time alone does not define cure energy.
  4. Keep film off flexing snap roots.A hard 10–30 µm coating can crack during assembly.

UV coating versus the alternatives

Finishes engineers weigh against UV coating, and when each wins.

FinishCorrosionHardnessCosmeticCostThicknessChoose it when
UV coating
this page
25—90$$10–30 µm—
Clear Coating
UV coating vs Clear Coating →
201285$$15–50 µmwhen a non-UV cure route is required
Wet Painting
UV coating vs Wet Painting →
591090$$20–80 µmwhen opaque color matching is the primary requirement
CorrosionHardnessCosmeticLubricityEconomy
UV coatingClear Coating

The radar overlays UV coating with Clear Coating, its most common alternative — chosen when a non-UV cure route is required. Scores in the table are 0–100 across every finish in the catalog.

Cost, lead time and compliance

Relative cost

UV-Cured Coating is a standard-cost finish ($$): cheaper than about 60 % of the finishes FabDigit quotes.

Finishing is priced per part with a lot minimum, from FabDigit's own China-side rates. The exact figure appears on the instant quote once the part is uploaded.

Lead time and compliance

Added lead time2–5 working days
RoHSCompliant
NotesLow-solvent formulations are available; confirm uncured acrylate handling and exact product compliance.

What UV coating is used for

  • High-gloss bezels
  • Appliance buttons
  • Cosmetic caps
  • Display windows with qualified chemistry
  • Decorative printed parts

UV coating — frequently asked

how thick is UV coating on plastic

A typical engineered film is 10–30 µm. Specify dry-film thickness because gloss alone does not control buildup or cure.

how fast does UV coating cure

Exposed film can crosslink in seconds under a qualified lamp dose. Shadowed regions may not cure at all without part rotation, multiple lamps, or dual-cure chemistry.

does UV coating prevent scratches

It can improve scratch and stain resistance compared with uncoated plastic, but it is not scratch-proof. Hardness must be balanced against cracking on flexible parts.

can UV coating be used on polycarbonate

Yes, with a chemistry qualified for polycarbonate. Solvent attack and molded-in stress can cause crazing, so test production-grade parts.

does UV coating turn yellow

Some formulations yellow under heat or outdoor ultraviolet exposure while stabilized grades perform better. The exact resin, photoinitiator, thickness of 10–30 µm, and exposure determine color stability.