Surface Sealing

3D-print & moulding post-processing · Dip / immersion

Surface sealing fills connected pores in printed or cast parts with a compatible resin or sealant.

3D printing CastingPremium cost $$$Unchanged

Quote a part with Surface seal Compare 3d-print & moulding post-processing

What is Surface seal?

It can improve cleanability, moisture resistance, and leak performance but must be qualified for fluid, pressure, and temperature.

How it works

The clean dry part is brushed, sprayed, dipped, or vacuum impregnated with low-viscosity epoxy, cyanoacrylate, acrylic, or another qualified sealant. Vacuum assists penetration into connected pores; excess is drained and the chemistry cures. A surface film may reduce roughness toward Ra 1–10 µm (40–400 µin), but thickness and final texture are highly chemistry-dependent. Leak testing, not appearance, verifies sealing. The supplier must state chemistry, cure, and compatibility.

Why specify it

Reduces connected porosity
Improves cleanability
Can make parts liquid-tight after validation
Protects porous surfaces from moisture

Where it falls short

Adds chemistry-specific film and dimensions
Does not repair structural voids
Temperature and fluid compatibility vary
Pressure tightness requires testing

Surface seal at a glance

Surface seal is a middle-of-the-range finish; its best score is cosmetic quality (55 of 100), at a premium cost. Surface hardness is not rated: the finish leaves the part's own surface.

Corrosion protectionLow30 / 100

Surface hardnessNot rated—

Cosmetic qualityGood55 / 100

LubricityLow20 / 100

Relative costPremium40 / 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.

Surface seal key numbers

Typical values from the governing specifications and shop practice; bars are this finish against the highest value among 3d-print & moulding post-processing finishes.

Thickness≥ 0 µm≥ 0 mil

Thickness

Penetrating systems may leave little surface film; coating sealers vary by chemistry. Typical finished Ra may be 1–10 µm (40–400 µin).

Electrical

Unchanged

Colours

clear
custom

Appearance

Clear to tinted sealed surface, from near-original matte to coated gloss.

Specifications for Surface seal

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

VACUUM IMPREGNATE POROUS PRINT WITH SUPPLIER-QUALIFIED CLEAR SEALER; MASK THREADS AND DATUM A; LEAK TEST AT 200 kPa FOR 10 min, ZERO VISIBLE BUBBLES

Which materials take Surface seal?

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

Material family	Verdict	Notes
Binder Jet	Yes	Infiltration and sealing are common but chemistry depends on part material.
MJF	Yes	Use where validated leak performance is needed beyond depowdering.
Polymer	Yes	Common on porous printed nylon and FDM parts.
SLS	Yes	Porous nylon can be sealed with a qualified compatible system.
DMLS / SLM	With care	Vacuum impregnation can close residual porosity; it does not fix lack-of-fusion defects.
FDM	With care	Layer-path leaks may require coating rather than simple pore impregnation.
Aluminum	Limited	Vacuum impregnation is for porous cast or AM aluminum, not dense wrought stock.
Copper Alloy	Limited	Only porous AM or PM copper needs impregnation.
Magnesium Alloy	Limited	Porous magnesium castings can be impregnated with a compatible sealer.
SLA	Limited	Fully dense SLA rarely needs impregnation; coating is usually enough.
Stainless Steel	Limited	Used on porous AM or PM stainless, not dense wrought stainless.
Steel	Limited	Used on porous PM or AM steel, not dense bar stock.
Titanium	Limited	DMLS titanium may be impregnated for pressure tightness after qualification.
Zinc Alloy	Limited	Porous zinc die castings are sometimes impregnated.
Brass	No	Dense brass does not need print sealing.

How Surface seal is applied, and what it does to the part

1Clean dry and depowder
2Mask
3Apply or vacuum impregnate sealant
4Drain and cure
5Clean and leak-test to requirement

Dimensions	Penetrating sealers may add little surface film, while coating sealers can alter fits and close small passages; qualify and inspect critical dimensions.
Build-up per side	≥ 0 µm — Buildup is supplier- and chemistry-specific; mask or post-machine fits.
Masking	Usually needed. Mask threads, bonding zones, precision fits, electrical contacts, and passages that must not retain sealant.
Electrical	Unchanged
Appearance	Clear to tinted sealed surface, from near-original matte to coated gloss.
Added lead time	2–7 working days on top of the bare part

Design rules for Surface seal

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

State fluid pressure and test duration.The word sealed is not measurable.
Name approved sealant chemistry.Temperature and chemical compatibility vary.
Provide drain paths.Excess resin can block cavities.
Mask bonds and fits.Sealer can impair adhesion and dimensions.

Surface seal versus the alternatives

Finishes engineers weigh against Surface seal, and when each wins.

Finish	Corrosion	Hardness	Cosmetic	Cost	Thickness	Choose it when
Surface seal this page	30	—	55	$$$	≥ 0 µm	—
Vapor Smoothing Surface seal vs Vapor Smoothing →	—	—	80	$$$	0 µm	when compatible nylon surface reflow can reduce porosity without an added sealer
Chemical Smoothing Surface seal vs Chemical Smoothing →	—	—	75	$$$	0 µm	when a solvent-compatible FDM surface needs reflow

Surface sealVapor Smoothing

The radar overlays Surface seal with Vapor Smoothing, its most common alternative — chosen when compatible nylon surface reflow can reduce porosity without an added sealer. Scores in the table are 0–100 across every finish in the catalog.

Cost, lead time and compliance

Relative cost

Surface Sealing is a premium-cost finish ($$$): cheaper than about 55 % 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	2–7 working days
RoHS	Compliant
Notes	Cured status does not establish food contact or biocompatibility; manage uncured resin and solvent as specified by the supplier.

What Surface seal is used for

SLS and MJF fluid housings
Binder-jet parts
Porous castings
Printed vacuum fixtures

Surface seal — frequently asked

does sealing make SLS parts waterproof

A qualified sealer can reduce connected porosity and pass a defined leak test. It is not automatically waterproof without a stated pressure, fluid, duration, and acceptance criterion.

what Ra does surface sealing produce

A broad practical range is Ra 1–10 µm (40–400 µin), but penetrating and film-forming sealers differ greatly. Measure the qualified system rather than relying on this range.

vacuum impregnation vs surface coating

Vacuum impregnation drives low-viscosity resin into connected pores and may leave little film. Surface coating intentionally forms a layer and changes dimensions and appearance more.

does print sealing change dimensions

It can. Film-forming sealers add thickness and can close holes or threads, while penetrating sealers usually have less buildup.

how do you test a sealed 3d print

Use the actual service fluid or an approved leak medium at a specified pressure and duration. For example, a drawing can require 200 kPa for 10 minutes with zero visible bubbles.