At NEDC, we convert a wide range of conductive elastomers for EMI/RFI shielding applications. Two of the most commonly specified nickel-aluminum filled materials are Cho-Seal 6502 and Cho-Seal 6503.
These materials are closely related — same filler system, similar mechanical feel — yet their base polymer difference makes them suited for very different operating environments.
Below is a clear, corrected breakdown of the differences, sheet nomenclature, and best-fit applications.
Use of Nickel Aluminum Filler in EMI Gasketing Applications
These materials are used in applications where additional requirements of galvanic corrosion are required, and in the case of Cho-Seal 6503 fluorosilicone material – it imparts good resistance against fluids in addition to the galvanic corrosion.
Correct Base Polymer Difference (MOST IMPORTANT)
Cho-Seal 6502 → SILICONE (Nickel-Aluminum filled)
General-purpose conductive silicone for EMI shielding, great in standard environments.
Cho-Seal 6503 → FLUOROSILICONE (Nickel-Aluminum filled)
Fuel-resistant conductive fluorosilicone for EMI shielding in harsh chemical environments.
This is the defining contrast:
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6502 is the silicone standard EMI silicone in nickel/aluminum.
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6503 is the chemically resistant fluorosilicone upgrade in nickel/aluminum.
Mechanical & Electrical Differences
| Property | Cho-Seal 6502 (Silicone) | Cho-Seal 6503 (Fluorosilicone) |
|---|---|---|
| Durometer | ~50 Shore A | ~60 Shore A |
| Compression Behavior | Softer, lower closure force | Slightly firmer |
| Volume Resistivity | Very good | Slightly higher (due to fluorosilicone base) |
| Fluid Resistance | Moderate | Excellent (fuels, solvents, oils) |
| Environmental Sealing | Excellent | Excellent |
| Typical Use Cases | General EMI gaskets, electronics housings | Aerospace, fuel systems, chemical exposure |
Sheet Nomenclature for 6502 & 6503
Both materials follow the same structural nomenclature:
Where:
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40 = Conductive elastomer sheet family
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XX = Thickness designator
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1020 = Sheet construction code
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6502 / 6503 = Material type
Below is the full, filled-in thickness mapping for both materials.
Cho-Seal 6502 Sheet Codes (Silicone)
| Sheet Code | Approx. Thickness |
|---|---|
| 40-10-1020-6502 | ~0.010″ |
| 40-20-1020-6502 | ~0.020″ |
| 40-30-1020-6502 | ~0.030″ |
| 40-40-1020-6502 | ~0.093″ |
| 40-50-1020-6502 | ~0.125″ |
| 40-60-1020-6502 | ~0.045″ |
Cho-Seal 6503 Sheet Codes (Fluorosilicone)
(Same structure and thickness availability)
| Sheet Code | Approx. Thickness |
|---|---|
| 40-10-1020-6503 | ~0.010″ |
| 40-20-1020-6503 | ~0.020″ |
| 40-30-1020-6503 | ~0.030″ |
| 40-40-1020-6503 | ~0.093″ |
| 40-50-1020-6503 | ~0.125″ |
| 40-60-1020-6503 | ~0.045″ |
How to Choose Between 6502 and 6503
The Nickel-Aluminum option is used for applications where corrosion cannot be afforded. Nickel Aluminum fillers are used in applications to prevent galvanic corrosion. This is even superior to other materials such as Cho-Seal 1298 when it comes to galvanic corrosion.
Choose Cho-Seal 6502 (Silicone) when:
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The environment does not include fuels or solvents
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You need a cost-effective conductive silicone
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You want a slightly softer gasket
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The enclosure sees water, humidity, dust, or general outdoor exposure
Choose Cho-Seal 6503 (Fluorosilicone) when:
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The enclosure sees jet fuel, diesel, gasoline, oils, hydraulic fluid, solvents
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You need EMI shielding plus chemical resistance
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You’re designing for aerospace, industrial fluids, UAV systems, or hazard environments
Final Thoughts
Cho-Seal 6502 and 6503 look similar at a glance — nickel-aluminum filled conductive elastomers — but their polymer backbones are what drive selection.
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Silicone (Cho-Seal 6502) is the everyday workhorse.
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Fluorosilicone (Cho-Seal 6503) is the chemically resistant specialist.
At NEDC, we convert both into precision-cut gaskets, strips, frames, and prototype components. If your design requires EMI shielding plus environmental sealing, the right choice between silicone and fluorosilicone is critical.