'Stamped Metal Gaskets and Seals: Materials and Finish'
Short answer: stamped metal gaskets seal joints where rubber alone would fail — high temperature, high pressure, or aggressive fluids. They work by compressing a formed metal bead or a stack of thin steel layers to create a controlled sealing load, and their performance depends on three choices: base material (stainless, copper or spring steel), the embossed or layered geometry, and the coating that fills micro-leaks. A well-designed stamped gasket holds a seal from cryogenic temperatures up to roughly 400-600 °C in stainless, where elastomers are long gone.
Metal gaskets are a precision stamping problem wearing a sealing hat. The part must be flat enough to seat, stiff enough to carry the bolt load, deformable enough to conform to surface imperfections, and stable enough to hold that seal across thermal cycling. This guide covers the main gasket types, how to select material and coating, and the design rules that decide whether a gasket seals or weeps.
Types of Stamped Metal Gaskets
Flat shim gaskets are simple blanked profiles that seal by clamping force alone, used for low-pressure or low-temperature joints. Embossed (beaded) gaskets add a raised ring or bead stamped into the metal; when the joint is bolted, the bead compresses like a spring and concentrates the sealing load along the contact line. Multi-layer steel (MLS) gaskets stack two to five thin steel sheets, some embossed, with the layers acting in series to give controlled compliance and excellent spring-back.
Spiral-wound gaskets combine a stamped, pre-formed metal winding with a softer filler strip, giving high recovery under load. Crush washers — often copper or aluminum — deform permanently to seal a single-use joint such as a drain plug. RF and EMI gaskets are a related family where the "seal" is electrical continuity rather than fluid containment, with stamped fingers or a conductive mesh doing the work.
Materials for Metal Gaskets
Material choice sets the temperature ceiling, corrosion resistance and available spring-back.
| Material | Typical temperature range | Corrosion resistance | Spring / recovery | Typical use |
|---|---|---|---|---|
| Stainless 301 | -40 to +400 °C | Good | Excellent (spring temper) | Embossed and MLS layers |
| Stainless 304 | -200 to +600 °C | Very good | Good | General high-temp gaskets |
| Stainless 316 | -200 to +600 °C | Excellent | Good | Chemical and marine joints |
| Spring steel (C67S, 65Mn) | -40 to +250 °C | Poor without coating | Excellent | Crush and load-bearing shims |
| Copper C110 | -200 to +300 °C | Moderate | High ductility | Crush washers, soft seals |
| Aluminum 1050/5052 | -200 to +200 °C | Moderate | High ductility | Lightweight crush seals, heat spread |
| Brass C2600 | -40 to +200 °C | Moderate | Good | Low-cost fluid fittings |
For high-temperature or corrosive joints, 304 or 316 stainless is the default. Where the joint must spring back repeatedly, a spring-temper grade such as 301 is preferred because it recovers its shape after compression. Copper and aluminum are chosen when the gasket is meant to deform permanently to fill a rough surface. The broader stamping materials guide covers gauge, temper and flatness for these strip grades.
Coatings and Finishes
The base metal often cannot seal on its own; a coating fills microscopic surface roughness and prevents galvanic corrosion.
| Coating / finish | Purpose | Temperature limit | Typical thickness |
|---|---|---|---|
| PTFE | Low friction, chemical resistance | ~260 °C | 5-25 µm |
| Graphite | Dry lubrication, high temperature | ~500 °C | 5-20 µm |
| Nitrile / NBR elastomer | Soft conforming seal | ~120 °C | 10-50 µm |
| Nickel plating | Corrosion resistance, solderability | ~400 °C | 2-10 µm |
| Zinc / chromate | Corrosion resistance on steel | ~120 °C | 5-15 µm |
| Silicone | Wide temperature, soft seal | ~200 °C | 20-100 µm |
Coatings are usually applied to one or both faces by roll, spray or dip. For MLS gaskets, each steel layer typically carries a thin anti-friction coating so the layers slide instead of galling during compression. For a chemical joint, PTFE on the sealing bead gives both chemical resistance and controlled sliding. Specify coating thickness and coverage explicitly on the drawing, because under-coating is a common hidden cause of slow leaks.
Design and Manufacturing Considerations
The bead is the heart of an embossed gasket. Bead height, width and material thickness set the sealing load and the recovery. A taller bead compresses further and conforms better but needs a stiffer bolt or a compression stop; a short, wide bead resists over-compression but conforms less. Design the joint so the bead compresses a defined percentage of its height — not to flat — because a fully flattened bead has no recovery left for thermal cycling.
Flatness and burr control matter as much as the bead. A gasket that is not flat cannot seat evenly, so it is usually stamped to ±0.05 mm on critical features and inspected for flatness across the sealing face. Burrs on the sealing edge can bridge the joint or damage a mating face, so deburring is often a required secondary operation. Tolerances on port openings and bolt holes are held tight to keep sealing load even; the metal stamping tolerances guide explains how these limits are specified.
For joints exposed to outdoor or marine environments, corrosion-resistant stamping practices — correct alloy, coating and edge protection — decide whether the gasket survives years or months.
Sealing Performance and Testing
A gasket's job is measured by leak rate under pressure, its recovery after compression, and its durability through thermal or chemical cycling. Suppliers typically confirm raw-material certificates and dimensions, then the customer leak-tests the assembled joint. For critical joints, compression-set and load-retention tests quantify how much sealing force remains after time and temperature.
At BQUQ we ship stamped gaskets and seal parts with dimensional inspection data and material traceability, and we can add flatness, burr and coating-thickness checks to the quality plan when the joint is critical.
Frequently Asked Questions
Q: What temperature can a stamped metal gasket handle?
A: A 304 or 316 stainless gasket can seal up to roughly 600 °C, far beyond any elastomer. Copper and aluminum crush seals work to about 200-300 °C, and spring-steel gaskets with zinc coating are best kept below about 120 °C because of the coating. Match the alloy and coating to your actual operating temperature.
Q: What is the difference between an MLS gasket and an embossed gasket?
A: An embossed gasket uses a raised bead stamped into a single metal sheet to concentrate sealing load. An MLS gasket stacks several thin steel layers, some embossed, so the layers act together for higher recovery and better fatigue resistance. MLS suits demanding, high-pressure joints; embossed suits simpler, lower-cost seals.
Q: How tight a tolerance can stamped gaskets hold?
A: Stamped metal gaskets normally hold ±0.1 mm on general profile dimensions and about ±0.05 mm on critical sealing features. Port openings and bolt-hole positions are often held tighter to keep the sealing load even. Tighter than that usually requires a secondary finishing operation.
Q: Why do metal gaskets need a coating?
A: The metal itself rarely seals perfectly because microscale surface roughness lets fluid creep through. A coating such as PTFE, graphite or an elastomer fills those gaps, lowers friction and adds corrosion protection. On MLS gaskets the coating also lets layers slide instead of galling.
Q: Can you produce gaskets in low volume?
A: Yes. Short-run tooling supports low-volume gasket production, and there is no fixed MOQ. Send the drawing with material, coating, temperature and pressure to sc@bquq.com, and BQUQ returns an indicative quote within 12 working hours.
Related Resources
- Stamping Materials Guide: choosing gauge, temper and alloy for stamped strip parts.
- Metal Stamping Service: stamped gaskets, shims and seal parts from a Dongguan source factory.
- About BQUQ: an ISO9001-certified source factory running stamping, CNC, springs, collets and heat sinks under one roof.
- Contact us: send your drawing to sc@bquq.com for a quote within 12 working hours.
Authored by the BQUQ Engineering Team. BQUQ is an ISO9001-certified source factory in Dongguan, China, running CNC machining, metal stamping, custom springs, heat sink and collet lines under one roof. Send drawings to sc@bquq.com or WhatsApp +86 13713157787 for a quote within 12 working hours. www.bquq.com
