Surface family
Metal body panels: which paint gauge reads steel and aluminum
Steel panels need a magnetic (Fe) gauge, aluminum panels an eddy-current (NFe) gauge. Both read the whole paint stack down to the metal.
Also listed as metal panels, Fe/NFe panels
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Short answer
Paint over steel is measured with a magnetic (Fe) gauge and paint over aluminum with an eddy-current (NFe) gauge, DeFelsko says. Either way the number is the full distance from the probe to the metal: primer, color, clear coat, any repaint, filler and dirt together. A combination Fe/NFe gauge covers both, which matters because one car can mix steel and aluminum panels.
What they share
- Material
- Steel and iron (ferrous) or aluminum and other non-ferrous metals[1]UNI-T: the measured object must be metal with a non-conductive coating.
- Gauge mode
- Fe on steel, NFe on aluminum; a combination (FN) gauge does both[1][4]DeFelsko's PosiTector 6000 probes come as F (ferrous), N (non-ferrous) and FN (both).
- What the reading includes
- Everything between the probe and the metal: primer, base color, clear coat, any repaint, filler and dirt[3]DeFelsko: magnetic and eddy-current gauges make no distinction between layers.
- Published thickness figures
- DeFelsko: factory paint typically 100-180 µm, with no absolute right thickness[3]A typical range, not a pass/fail line. See [factory paint](/surfaces/factory-paint) for other published ranges.
- Polishing note
- A Fe/NFe reading cannot tell you how much clear coat is left[3]The reading is total coating thickness, not clear-coat thickness. See [clear coat](/surfaces/clear-coat) for DeFelsko's figures.
- Inspection tip
- Look for consistent thickness around the car; measure near seams about one inch from edges[2]
Watch out for
- One car can mix metals. DeFelsko notes that recent vehicles can combine steel doors and fenders with aluminum hoods and roofs. A steel-only (Fe) gauge is not the tool for the aluminum panels.
- The number is the whole stack. Magnetic and eddy-current gauges cannot separate clear coat from color, primer, repaint or filler. A reading is a thickness, not a diagnosis.
- Thin metal can limit accuracy. Elcometer says the 311's stated accuracy needs at least 800 µm of steel or 300 µm of aluminum under the probe; Linshang lists minimum substrates of 0.2 mm (Fe) and 0.05 mm (NFe) for the LS221. Check the minimum substrate in your gauge's specification.
What fits
Product details below are the seller's own description unless a source is shown. Pick the variant named for each item.
Fe/NFe combination gauge
UNI-T UT343E Fe/NFe coating thickness gauge (Bluetooth, 0-2000 µm)Choose the UT343E (Bluetooth, 0-2000 µm), the only variant listed.
UNI-T specifies it for ferrous and non-ferrous substrates with automatic or manual substrate identification. The AliExpress store uses UNI-T's name, but UNI-T's own where-to-buy page links no AliExpress store, so treat the seller as unconfirmed. UNI-T's page lists CE and UKCA marks only.
Sold by UNI-T Official Store
View on AliExpress Opens aliexpress.us
Paint and surfaces in this family
- Steel body panels steel panels, ferrous panels, Fe panels
- Aluminum body panels aluminum panels, non-ferrous panels, NFe panels
Pick the panel: steel panels or aluminum panels. Bumpers and fiberglass parts are covered under non-metal panels.
Questions
Do I need a different gauge for aluminum panels?
You need a gauge with an NFe (eddy-current) mode. DeFelsko says paint over steel is measured magnetically and paint over aluminum with eddy current; a combination Fe/NFe gauge does both.[2][1]
Does a paint gauge measure just the paint?
It measures everything between the probe and the metal. DeFelsko says that includes primer, base color, clear coat, any repaint, filler and dirt, with no distinction between layers.[3]