What it is
made of.
A seal is chosen by its materials more than by its shape. This is a plain reference to what the common face and elastomer materials do well and where they stop — general engineering knowledge, so you can read our product pages with context.
Seal face materials
Carbon (resin or antimony impregnated)
The traditional soft face, run against a harder mating ring. Self-lubricating, forgiving of brief dry contact, and the usual first choice where the duty allows it.
- Good dry-running tolerance for short periods
- Conforms to the mating face, so it beds in
- Wide chemical compatibility depending on impregnant
- Wears faster than hard faces
- Not suited to abrasive-laden media
- Impregnant, not the carbon, usually sets the chemical limit
Silicon CarbideSiC
A hard, highly chemically resistant ceramic with excellent thermal conductivity. The common choice for aggressive and abrasive service.
- Very high hardness, so it resists abrasive wear
- Broad chemical resistance including strong acids and alkalis
- Conducts heat away from the faces well
- Brittle — intolerant of impact and thermal shock
- Poor dry-running behaviour when run against itself
- Higher cost than carbon or ceramic
Tungsten CarbideTC
Extremely hard and far tougher than the ceramics, so it survives mechanical shock that would crack silicon carbide.
- High hardness with good fracture toughness
- Handles abrasive and high-pressure duty
- Better thermal shock resistance than SiC
- Binder phase (cobalt or nickel) governs corrosion resistance
- Heavy, and expensive in large sizes
- Cobalt-bound grades are attacked by some acids
Ceramic (alumina)
An economical hard face, chemically resistant to many media, generally run against carbon.
- Low cost
- Good corrosion resistance in many services
- Hard-wearing
- Poor thermal conductivity, so it runs hotter
- Vulnerable to thermal shock
- Not suited to duties where SiC or TC would be specified
Stellite / hard-faced alloys
A cobalt-chromium hardfacing applied to a metal substrate, historically common on larger and repair-friendly seals.
- Repairable by re-facing
- Tough
- Suits larger diameters
- Lower hardness than the carbides
- Less chemically resistant than ceramics
Face pairs matter as much as the individual materials. A soft face against a hard face (carbon against silicon carbide, for example) generally runs cooler and more forgivingly than two hard faces, while hard-against-hard is specified where the medium carries solids that would embed in a carbon face. Which pairing suits a given duty depends on the medium, the temperature, the pressure and the speed together — it is a selection decision, not a lookup.
Secondary seals & elastomers
The secondary seal is usually what decides whether a seal survives the chemistry — the faces often outlast it.
| Material | Character | Suits | Avoid |
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| NitrileNBR | The general-purpose secondary seal — inexpensive and good with oils. |
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| EPDM | Strong with water, steam and many polar chemicals; poor with petroleum oils. |
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| FluoroelastomerFKM / Viton | The common upgrade: broad chemical resistance and good high-temperature capability. |
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| AflasFEPM | Handles bases and amines that attack conventional fluoroelastomers. |
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| PTFE | Not an elastomer but used as a secondary seal where nothing else survives — chemically near-inert, with almost no elastic recovery. |
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| PerfluoroelastomerFFKM | Near-universal chemical resistance with elastomeric behaviour. Specified where the media defeats FKM and PTFE will not do. |
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Materials follow the media.
Tell us what you are pumping and at what temperature and pressure, and our engineers will specify the faces, elastomers and metallurgy for it.