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Sealing and Shielding a Seam at Once: Combined Ingress and EMI Gaskets for Naval and Ground Platforms
A naval or topside electronics enclosure faces two threats at the same joint: electromagnetic energy must stay contained, so the seam must be electrically continuous, and salt water must stay out, so the same seam must be sealed. Treat these as two problems and you get two gaskets and two ways to fail. Treat them as one and a single conductive elastomer closes both. This article explains the combined-function gasket, the corrosion trap at the conductive interface, and why ingress and EMI are tested on the enclosure, not the gasket.
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One seam, two enemies: the signal getting out and the sea getting in
A naval or topside electronics enclosure faces two threats at the same joint. Electromagnetic energy must be kept inside the box, or outside it, so the seam has to be electrically continuous. And salt water, spray, and humidity must be kept out, so the same seam has to be environmentally sealed. Treat these as two separate problems and you end up with two gaskets, two seal lines, and two ways to fail.
Treat them as one and a single conductive elastomer can close both at once, which is why combined-function gaskets dominate marine and ground-platform design.
Why two separate gaskets is the harder path
Specifying a dedicated shield gasket and a dedicated weather gasket sounds safe, but it multiplies problems. Each gasket needs its own groove or land, widening the flange and complicating the closure. Each adds a seal interface that can leak or lose contact. And the two can fight each other: the firmer shield gasket may hold the lid off the softer weather seal, so neither does its job well.
A single conductive elastomer that seals and shields in one cross-section collapses two failure-prone interfaces into one designed interface, with one closure force to manage instead of two.
How a conductive elastomer seals and shields at once
A conductive elastomer is a silicone (or fluorosilicone) gasket loaded with conductive filler. The elastomer matrix seals exactly like any compression gasket, conforming to the flange and excluding water. The conductive filler gives the same part the electrical continuity to bridge the gap across the seam, completing the shielded enclosure so electromagnetic energy cannot leak through the joint.
One compression sets both functions, which is why closure force and groove design matter so much: too little compression and both the seal and the shield degrade together. These grades are commonly evaluated to MIL-DTL-83528.
The corrosion trap at the conductive interface
The gasket-to-flange contact is a galvanic junction
A conductive gasket is, by design, in electrical contact with the housing metal, and on a marine platform that contact sees salt water. That is the recipe for a galvanic cell at the very interface the shield depends on: the conductive filler and the housing metal sit at different points on the galvanic series, and the electrolyte completes the circuit. Left unmanaged, the flange corrodes or the contact resistance climbs, and the shield quietly degrades.
Corrosion-resistant grades and finish matching
The answer is to choose a conductive grade formulated for marine exposure and to match the housing finish so the couple is benign. Corrosion-resistant conductive silicone grades exist precisely for this, with salt-fog behavior commonly evaluated to ASTM B117. The gasket selection and the housing finish are a pair; choosing one without the other leaves the galvanic question half-answered.
The seal protects the shield
The two functions are not independent. If the environmental seal fails and water reaches the conductive interface, corrosion attacks the very path that provides shielding, so a leak becomes a shielding failure over time. Keeping the seal intact is part of keeping the shield intact, which is another argument for one well-compressed combined gasket over two marginal ones.
Ingress and EMI are tested on the enclosure, not the gasket
It is worth stating plainly: a gasket material does not carry an IP rating or an EMI qualification by itself. An ingress class under IEC 60529 is established by testing the finished, closed enclosure, and electromagnetic compliance under MIL-STD-461 is established by testing the system. The gasket is an enabler that lets a well-designed enclosure reach those targets, not a substitute for the test. Specifying the right combined gasket gives the enclosure its best chance; demonstrating the rating is the program's job.
How H-O Products helps
H-O Products die-cuts, waterjet-cuts, and laminates conductive and environmental gaskets to your drawing in Winsted, Connecticut; we do not manufacture the elastomers in-house. We cut combined-function conductive gaskets to your seam geometry, add adhesive backings or carriers, and kit gasket sets, including retrofit and depot sets, to work orders, all under our ISO 9001:2015 certified quality management system with lot-coded traceability and the maker's TDS on the order.
Frequently asked questions
Why use one combined gasket instead of separate shield and weather seals?
Two gaskets need two grooves, add two seal interfaces that can fail, and can fight each other if the firmer shield gasket holds the lid off the softer weather seal. A single conductive elastomer seals and shields in one cross-section with one closure force to manage, collapsing two failure-prone interfaces into one designed interface. That is why combined-function gaskets dominate marine and ground-platform seams.
How does a conductive elastomer shield and seal at the same time?
It is a silicone or fluorosilicone gasket loaded with conductive filler. The elastomer matrix seals like any compression gasket, while the conductive filler gives electrical continuity across the seam to complete the shielded enclosure. One compression sets both functions, so closure force and groove design are critical: too little compression and the seal and the shield degrade together. These grades are commonly evaluated to MIL-DTL-83528.
Why do conductive gaskets corrode on naval platforms?
Because a conductive gasket is in electrical contact with the housing metal by design, and on a marine platform that contact sees salt water, forming a galvanic cell at the very interface the shield depends on. The fix is a corrosion-resistant conductive grade matched to a compatible housing finish, with salt-fog behavior commonly evaluated to ASTM B117. The gasket and the finish are a pair; the corrosion judgment belongs to your program.
Does the combined gasket make my enclosure IP67 and MIL-STD-461 compliant?
No material does that on its own. An IP class under IEC 60529 is established by testing the finished enclosure, and EMI compliance under MIL-STD-461 is established by testing the system. The gasket enables a well-designed enclosure to reach those targets; demonstrating the rating is the program's job. H-O converts the gasket to your drawing and makes no IP-rating or EMI-qualification determination.
Can H-O cut gasket sets for retrofit and depot work?
Yes. We die-cut and waterjet conductive and environmental gaskets to existing seam geometry, reverse-engineer from a sample or a worn gasket, and kit complete sets for retrofit and depot maintenance, all under our ISO 9001:2015 certified quality management system with lot-coded traceability. Send the seam geometry or a sample gasket and we will quote the converted set.
Have a combined seal-and-shield seam reviewed
Send the seam geometry, the platform and corrosion exposure, and whether the joint must shield, seal, or both, and we will recommend a combined-gasket direction and quote converted parts to your drawing.
Samples typically ship in 3 to 5 business days for common die-cut configurations on materials we keep on hand; standard production runs about two weeks after drawing approval; expedited service is available. MOQ varies by material and part.
Family-owned in Winsted, Connecticut since 1971 · ISO 9001:2015 certified · OEMs worldwide send us a drawing — and get back their part.
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Send H-O your drawing or describe the part—engineering reviews every RFQ and converts samples on your geometry.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
References
- MIL-DTL-83528 (conductive elastomer spec); MIL-STD-461 (EMI test methods); IEC 60529 (ingress protection). Cited by designation; ingress and EMI results are established by testing the finished enclosure, not the gasket.
- ASTM B117 (salt fog); ASTM E662 (smoke density); ASTM D1056 (flexible cellular rubber); ASTM C1166 (flame propagation of gasket materials). The galvanic series is standard electrochemistry, summarized qualitatively; H-O makes no corrosion determination.
- Manufacturer technical data sheets: conductive silicone and corrosion-resistant conductive elastomers, conductive sponge, EPDM and neoprene foam, low-smoke / low-flame / low-toxicity grades.
This article summarizes material-selection principles for defense-electronics, ground-vehicle, and naval platforms using the families and method designations cited on the parent application page. H-O Products supplies converted materials only; we do not design, integrate, or test platforms or weapons systems. Comparisons are qualitative; shielding, sealing, and thermal values are per each grade's current technical data sheet, and no test results are quoted.
MIL-DTL-83528, MIL-STD-461, MIL-STD-810, IEC 60529, and other designations are named for orientation only; H-O holds no QPL listing or program certification and makes no qualification, IP-rating, or compliance determinations. All parts are custom manufactured to order; minimum production run quantities vary by material and part. H-O is a converter, not a raw-material producer.