EMI Shielding Coating

Coatings for plastics · Spray applied

EMI shielding coating is a conductive metal-filled paint applied mainly to the inside of nonconductive enclosures.

Injection molding 3D printingHigh cost $$$$Conductive

Quote a part with EMI coating Compare coatings for plastics

EMI Shielding Coating on a machined part

What is EMI coating?

It creates a continuous electrical shell that attenuates electromagnetic fields when correctly bonded across seams and to chassis ground.

How it works

Silver, copper, nickel, or hybrid conductive particles are dispersed in a polymer binder and sprayed onto cleaned, activated plastic. After curing, particle-to-particle contact forms a conductive network. Shielding depends not only on the coating but also on thickness, continuity, aperture size, seam design, gasket contact, and grounding. Overspray or a decorative topcoat can insulate intended contact lands, so the grounding architecture and masking plan must be designed together.

Why specify it

Converts polymer housings into conductive shielding surfaces
Typical v1 film is 15–30 µm
Spray reaches complex interior enclosure geometry
Can be locally masked around antennas and high-voltage clearances

Where it falls short

Scratches and seams interrupt current paths
Deep recesses can receive low film thickness
Metal-filled coatings add cost and galvanic compatibility concerns
Shielding cannot be guaranteed from coating thickness alone

EMI coating at a glance

EMI coating is a middle-of-the-range finish; its best score is cosmetic quality (25 of 100), at a high cost. Surface hardness is not rated: the finish leaves the part's own surface.

Corrosion protectionLow20 / 100

Surface hardnessNot rated—

Cosmetic qualityLow25 / 100

LubricityLow15 / 100

Relative costHigh65 / 100

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.

EMI 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.

Thickness15–30 µm0.59–1.2 mil

Thickness

15–30 µm in the v1 catalog; exact product data sheet controls

Electrical

Conductive

Colours

silver
copper
gray

Appearance

Functional metallic gray, silver, or copper interior film; usually not selected as a cosmetic exterior.

Specifications for EMI 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

NICKEL/COPPER EMI SHIELDING COATING ON ENCLOSURE INTERIOR, 20–30 µm DFT; MAINTAIN CONTINUOUS COATING ACROSS GASKET LANDS; MASK ANTENNA KEEP-OUT AND CONNECTOR INSULATORS

Which materials take EMI coating?

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

Material family	Verdict	Notes
Polymer	Yes	Primary use; surface activation or primer may be required.
Brass	With care	Clean tarnish and qualify adhesion.
Composite	With care	Seal porosity and account for any conductive reinforcement.
Copper Alloy	With care	Clean tarnish and qualify adhesion; some solvents stain copper.
FDM	With care	Seal layer lines so the conductive film is continuous across seams.
Magnesium Alloy	With care	Needs conversion coating or primer before an organic film.
MJF	With care	Clean and seal before conductive coating.
SLA	With care	Post-cure and verify solvent compatibility.
SLS	With care	Seal porous nylon before applying a continuous shield.
Zinc Alloy	With care	Needs conversion coating or primer; some solvents attack zinc.
Aluminum	Limited	Bulk aluminum already shields; coating is for polymer housings, not the metal itself.
Stainless Steel	Limited	Stainless already conducts; coating is for polymer enclosures.
Steel	Limited	Bulk steel already shields; this coating is for polymer enclosures.
Titanium	Limited	Titanium already conducts; coating is for polymer enclosures.
DMLS / SLM	No	Metal AM enclosures already provide a conductive shield.

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

1Clean and activate plastic
2Mask
3Prime if required
4Mix conductive coating
5Spray controlled passes
6Cure
7Measure thickness and resistance
8Verify assembled shielding performance

Dimensions	Allow 15–30 µm in grooves and seams; keep gasket contact lands coated but free of insulating topcoat.
Build-up per side	15–30 µm — Conductive dry film adds its thickness and must remain exposed at designed contact lands.
Masking	Usually needed. Mask antennas, connectors, creepage and clearance zones, threads, optical areas, and all surfaces not intended to join the shield.
Electrical	Conductive
Appearance	Functional metallic gray, silver, or copper interior film; usually not selected as a cosmetic exterior.
Added lead time	4–8 working days on top of the bare part

Design rules for EMI coating

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

Design a continuous conductive path across every enclosure seam.A conductive panel does not shield through an unbonded seam.
Keep apertures small relative to the shortest wavelength of concern.Coating cannot close an electromagnetic slot.
Expose coating at gasket and ground contacts.Decorative paint over the shield blocks electrical bonding.
Test the assembled enclosure, not a flat coupon alone.Geometry, cables, seams, and apertures dominate shielding effectiveness.

EMI coating versus the alternatives

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

Finish	Corrosion	Hardness	Cosmetic	Cost	Thickness	Choose it when
EMI coating this page	20	—	25	$$$$	15–30 µm	—
Conductive Coating EMI coating vs Conductive Coating →	15	—	20	$$$	15–50 µm	when conductivity is needed without a defined EMI enclosure function
Vacuum Metallization EMI coating vs Vacuum Metallization →	45	—	94	$$$$	0.05–1 µm	when a thinner deposited metal layer is preferred

EMI coatingConductive Coating

The radar overlays EMI coating with Conductive Coating, its most common alternative — chosen when conductivity is needed without a defined EMI enclosure function. Scores in the table are 0–100 across every finish in the catalog.

Cost, lead time and compliance

Relative cost

EMI Shielding Coating is a high-cost finish ($$$$): more expensive than about 73 % 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 time	4–8 working days
RoHS	Compliant
Notes	Confirm metal powder, binder, solvent, and restricted-substance compliance for the exact product.

What EMI coating is used for

Medical electronics housings
Radio enclosures
Instrument cases
Aerospace electronics covers
Printed prototype enclosures

EMI coating — frequently asked

does conductive paint block EMI

Metal-filled paint can form an effective shield on a plastic enclosure, but coating alone is not enough. Seams, apertures, grounding, and gasket contact control assembled performance.

how thick is EMI shielding coating

The v1 catalog uses 15–30 µm for this class. Follow the named product data sheet and verify resistance and shielding on the assembled enclosure.

nickel vs copper EMI shielding paint

Copper-filled systems generally offer high conductivity, while nickel-containing systems can provide different oxidation and cost tradeoffs. Selection must also consider galvanic contacts and the required frequency range.

can EMI coating be painted over

A decorative topcoat can cover non-contact areas if the system is compatible. Ground and gasket lands must remain electrically exposed because an insulating topcoat breaks the shield bond.

does EMI coating affect threads

A 15–30 µm film can tighten threads and create uncontrolled conductive debris during assembly. Mask ordinary threads, or explicitly design a qualified conductive fastening interface.