A metal RFID card needs a construction engineered for its operating frequency. In LF and HF/NFC designs, the chip and coil antenna commonly sit behind a ferrite or shielding layer that reduces the metal face’s effect on the magnetic field. Ferrite is an iron-oxide-based ceramic material with high magnetic permeability and electrical resistance. Without suitable shielding or another engineered antenna arrangement, eddy currents can detune the antenna and severely reduce or prevent reading. UHF cards use a different RF architecture; an LF/HF ferrite-and-coil stack does not describe every metal RFID card.
Why nearby metal affects reading
LF and HF/NFC RFID readers work by magnetic coupling. Each reader emits an alternating field, the card's coil antenna picks up energy from it, and the chip answers. Put a sheet of conductive metal in front of that coil and the field induces circulating currents in the metal itself. Those eddy currents produce their own opposing field, canceling most of what reaches the antenna, and they shift the antenna's resonant frequency away from where the reader is listening. Both effects reduce available energy and can prevent a read.
This is the same physics that makes ordinary NFC stickers stop working when you put them on a laptop lid or a machine housing. The industry's answer there is the anti-metal tag, which is just a standard inlay with a thin ferrite sheet bonded behind it. Many HF/NFC metal cards use the same principle, engineered into the card body rather than added afterward. Payment-style metal cards add a second trick: a slot or aperture cut through the metal that breaks the eddy-current loop so the field can pass.
What is inside a working metal card
The finished stack matters more than the face material alone. The following layered construction is typical of LF/HF coil-based designs; UHF designs need their own antenna and mounting arrangement.
The antenna coil and chip sit between the faces, not behind bare metal. In this coil-based construction, shielding between the face and coil helps preserve the contactless reading function.
| Layer | Job | Typical detail |
|---|---|---|
| Front face | Appearance and marking surface | 304-family stainless, brass, copper, or steel with a PVD coating a few microns thick |
| Ferrite / shielding layer | Redirects the magnetic field away from the conductive face | A fraction of a millimeter thick, die-cut to the card outline |
| Antenna and chip | The RFID function itself | Coil tuned to the final stack, not to a generic card |
| Core or spacer | Holds flatness and sets finished thickness | Sets the finished thickness; confirm the complete construction rather than face-sheet thickness |
| Back face | Print, QR panel, serial numbers, legal text | Metal or a printable layer, depending on the build |
Because the antenna is tuned to the finished stack, thickness is not a free choice at the end of the process. Change the core and you change the tuning. That is why a metal card is quoted as a construction rather than a material, and why there is a page-by-page breakdown of the RF layer inside a metal card worth reading before you write a spec.
Frequency and chip choice
Metal does not remove any of the usual options, but it does change how much engineering each one needs.
| Frequency | Standard | Typical use | What metal changes |
|---|---|---|---|
| 125 kHz (LF) | Proprietary air interfaces | Legacy access control, rewritable credentials | Range is short to begin with, so the shielded build has less margin to lose |
| 13.56 MHz (HF / NFC) | ISO/IEC 14443A, ISO/IEC 15693 | Phone taps, access credentials, membership, encrypted AES-128 builds | The most common route for metal cards, and the one with the most proven constructions |
| 860–960 MHz (UHF) | ISO/IEC 18000-63 (EPC Gen2) | Asset tracking, longer-range identification | Antenna geometry and mounting dominate performance; placement testing is mandatory |
Whatever the frequency, one step does not change: an encoded sample is read on the exact phone, reader or lock the card will live with, before anyone runs a batch. A metal card that reads perfectly on a desktop USB reader can still fail on a wall reader with a different antenna and a metal backplate.
What metal changes in daily use
- Read distance can be shorter. Read distance depends on the finished antenna, shielding, reader and orientation; it can be shorter than with PVC. For a tap-on-contact reader nobody notices; for a reader people wave at from 4 cm away, test first.
- The card bends instead of snapping. PVC can crack visibly. Metal can take a permanent bend while still looking usable, so return checks should include flatness and reading performance.
- Confirm printer compatibility. Do not assume compatibility with a standard desktop thermal card printer or embosser. Factory marking is typical; any on-site process needs approval for the specific construction and equipment.
- Weight is the selling point and the surprise. The difference against a 0.76 mm PVC card is obvious in hand, and it varies with construction, so judge it on a physical sample rather than a number in a table.
- Scratches read as wear, not damage. Brushed and matte faces hide handling; mirror faces show every fingerprint under lobby lighting.
Where metal belongs, and where it does not
We build hotel key card programs in wood, plant-based board and recycled PVC, so the question we get is usually the honest version: should the whole property switch to metal? Almost never. Room keys are a fleet item that gets handled thousands of times, walks out of the building in guests' pockets, and often needs a room number printed at the desk. Metal is wrong on all three counts, and the cost per card is not close.
Brushed stainless is the reference build for metal RFID: a steel face whose conductivity is exactly why the construction behind it matters.
Metal earns its place where the card is a small population and a deliberate object. Residence and villa owners rather than nightly guests. Club, spa and dining memberships that stay in a wallet for years. Invitation and gift cards where the weight is part of the reveal. The general manager's own NFC business card. In those programs the card is a brand asset with a long life, and the premium disappears into a marketing budget rather than an operating one.
For everything issued at scale, the material decision is between wood, bio-based board and recycled PVC, which we compare in wooden vs BioBoard vs recycled PVC hotel key cards. If you are still choosing the technology rather than the material, what an RFID card is and our hotel key card guide cover the frequency and lock questions first.
Marking and finish decisions
Laser engraving on brass holds fine line work that would fill in on a printed plastic card.
Metal marking behaves nothing like card printing, and the finish you pick decides what marking looks good on it:
- Coated black steel faces can provide strong contrast. On suitable coated-steel configurations, engraving can remove the surface coating to reveal the underlying steel. The result depends on the metal, coating and marking process; confirm contrast and small details on a finished sample.
- Brass takes depth. It is a solid copper-zinc alloy rather than coated steel, softer under the tool, which is why deep engraving and enamel-style fills work on brass and not on thin plating.
- Copper is a living surface. Untreated it darkens toward patina. Decide at sample stage whether to clear-coat and hold the tone or let it age.
- Dark faces need a light panel for data. Grey-on-grey QR codes and serials fail scan tests. A printed panel behind them fixes it.
- Full color means UV print, usually over white ink. Metal has no white in it, so any light artwork needs a base layer laid down first.
What to check before you order
- An encoded sample read on your actual reader or lock, not a generic bench reader
- A dieline with any hole, slot or cut-through marked, reviewed against the antenna path before tooling
- Finished thickness confirmed against the reader slot or dispenser it has to fit
- Who encodes: factory-encoded and serialised, or delivered blank for your own system
- Edge and corner finish, which on metal is a visible design decision rather than a trim detail
Frequently asked questions
Do metal cards block RFID?
Conductive metal near an ordinary LF/HF coil antenna can detune it and impair reading. A finished metal RFID card uses frequency-specific shielding, antenna geometry or other engineering to address this. UHF needs a different antenna architecture. The proof is an encoded sample tested on the target reader before production.
Will a metal card work in our hotel lock?
It may work when the chip, protocol, encoding and construction match the 13.56 MHz lock. Read range can be shorter than on a plastic card, and lock readers vary in antenna design and mounting. Test one encoded card on the exact lock model, and on the desk encoder, before ordering a batch. Related reading: why hotel key cards stop working.
Can you print full color on a metal card?
Yes, with UV printing, normally over a white base layer so colors are not dragged toward the metal tone underneath. Laser marking and print are often combined on one card: engraved logo, printed data panel.
How thick is a metal RFID card?
An indicative range is 0.3–0.8 mm, but finished RFID thickness must be confirmed for the exact construction, with the standard CR80 outline of 85.60 × 53.98 mm. A standard PVC card is 0.76 mm, so a metal build can be thinner or slightly thicker than what your reader already accepts. That is a spec to confirm, not to assume.
If a metal build is genuinely what a project needs, metal RFID cards are documented there finish by finish, with the artwork and engraving specs. If the card in question is a room key for a whole property, ask us for a sample pack of wood, BioBoard and recycled PVC instead and put the three in your front desk team's hands.