Why Masking Is Harder for Electrocoating Than Other Finishes
When a customer needs certain surfaces of a part left completely bare — no coating, no finish, nothing — that's where masking comes in. It sounds simple, but as George Giering, President and CEO of Giering Metal Finishing, explains, masking is one of the most technically demanding parts of the metal finishing process, and it becomes even more difficult when the finish being applied is electrocoating.
Why Masking Matters in Metal Finishing
Not every surface on a part is meant to be coated. Threaded holes, electrical contacts, mating surfaces, and precision-machined features often need to stay bare metal so the part can still be assembled, grounded, or function correctly after finishing. If coating material gets into those areas, the part can be scrapped entirely which can be an expensive outcome for aerospace, defense, and medical components that are often already machined to tight tolerances. Masking exists to prevent exactly that.
The Many Ways to Mask a Part
Masking can be accomplished several different ways, and the right method usually comes down to volume and geometry. According to Giering, for smaller runs, one or two pieces, applying tape is often the most practical option. Giering works with several suppliers that provide high-temperature masking tape designed to survive the curing oven without peeling, thanks to a high-temperature adhesive backing built to withstand elevated bake temperatures.
For round features like holes, high-temperature masking plugs work almost like a cork in a wine bottle — simple, effective, and reusable. For male threaded features, such as studs, high-temperature caps slip over the feature to keep coating off the threads entirely.
When Custom Engineered Masks Make Sense
Tape and off-the-shelf plugs and caps work well for straightforward geometry, but not every part is that simple. When a surface is large, or a piece of geometry is especially complex, applying tape or a standard cap becomes too cumbersome, and too risky. In those cases, Giering brings in engineering resources, often working with a machine shop or wire fabrication shop, and in some cases suppliers who mold custom high-temperature caps and plugs to match the exact geometry of the part.
This is where Giering's engineering-driven approach sets it apart from finishers who avoid masking altogether. Many finishing shops don't want to take on masking work at all, given the risk of coating leakage into a protected area and the labor involved in carefully applying multiple masking materials to a single part. Giering treats masking as its own engineering discipline rather than an afterthought.
Why Electrocoating Masking Is Uniquely Difficult
Masking is challenging across every finishing process, but it's especially difficult with electrocoating, and George Giering uses a simple comparison to explain why: think of masking like wearing a shower cap. Wear a shower cap in the shower, and your hair stays dry. Wear that same shower cap in the bathtub, fully submerged, and your hair is going to get wet regardless.
That's the core challenge with electrocoating. Unlike spray-applied finishes such as powder coat or liquid paint, electrocoating is an immersion process — the entire part is submerged in a tank of coating material and an electrical charge draws the coating onto every conductive surface. Because the part is fully submerged rather than sprayed from one direction, it's far harder to keep coating material out of a masked area. There's no "line of sight" advantage the way there is with spray finishes; the fluid surrounds the part completely.
Despite that added difficulty, Giering routinely masks parts successfully for the electrocoating process, using the same combination of high-temperature tape, plugs, caps, and custom-engineered fixtures — just executed with tighter tolerances and more careful process control to account for full immersion.
Giering's Engineering-Driven Approach to Masking
Giering Metal Finishing has been solving these kinds of finishing challenges for aerospace, automotive, medical, and defense customers for more than 70 years, operating as an ISO 9001:2015 certified and ITAR-registered facility in Hamden, Connecticut. Masking often requires custom mechanical solutions rather than an off-the-shelf product, so Giering's engineering team gets involved early by reviewing part geometry and finishing requirements together, rather than treating masking as a separate afterthought once a part reaches the finishing line. This consultative, engineering-first approach is also discussed in more detail in Giering's overview of masking techniques across all finishing processes.
Frequently Asked Questions
Why does a part need masking during metal finishing?
A part needs masking when certain surfaces — like threaded holes, electrical contacts, or precision-machined features — must remain free of coating so the part can still be assembled or function correctly. Without masking, coating material would cover those areas, which can make a part unusable and require it to be scrapped and reworked.
What materials are used to mask parts before coating?
Common masking materials include high-temperature masking tape, molded plugs for holes, and caps for threaded studs or male features. For large surfaces or complex geometry, finishers often move to custom-engineered mechanical masks built specifically for that part, typically produced by a machine shop or supplier.
Why is masking harder for electrocoating than for powder coating or paint?
Electrocoating is an immersion process, meaning the entire part is submerged in the coating tank rather than sprayed. That makes it significantly harder to prevent coating material from reaching a masked area, since the fluid surrounds the part completely — compared to spray finishes, where coating is only applied from certain directions.
Can every part shape be masked, even complex geometry?
Yes, but complex geometry usually requires a custom-engineered solution rather than standard tape or caps. Finishers with engineering capabilities, like Giering Metal Finishing, can design and manufacture molded high-temperature plugs or fixtures that replicate the exact shape needed to protect a specific area during coating.
How do I know if my parts need custom masking versus standard tape and plugs?
If you're running a small quantity of simple parts, standard high-temperature tape, plugs, or caps are usually sufficient. If you have larger production volumes, complex geometry, or the part will be electrocoated, it's worth discussing your specific requirements with a finishing partner that has in-house masking engineering experience.
Talk to Giering About Your Masking Requirements
Masking is one of the most overlooked but critical steps in delivering a properly finished part — especially when electrocoating is involved. Giering Metal Finishing's engineering-driven approach means masking is planned alongside the coating process itself, not added as a last-minute step. If your project involves complex geometry, tight tolerances, or an electrocoating application, contact Giering Metal Finishing to discuss the right masking solution for your parts.
