The tag fails on a fridge or an appliance
A fridge door is a steel panel and an appliance fascia usually hides a metal chassis, so the plastic you can see is rarely the whole thickness. The tag is behaving normally and the surface is doing exactly what a conductive surface does.
What looks plastic and is not
A fridge door is steel with a painted or coated finish. Magnets stick to it, which is a free test anyone can run.
An appliance control fascia is often a thin plastic or glass layer over a metal chassis. The visible material is not the whole story.
A washing machine, an oven front, a dishwasher door and a microwave are all built on metal for structural and shielding reasons.
A plastic handle, a plastic trim strip or a plastic bin front is usually genuinely plastic, and that is where a tag has a chance.
Confirming it
Hold a magnet to the surface. If it sticks, you have ferrous metal and an ordinary tag will not work there.
A magnet does not detect aluminium, so a negative result is not a clearance. Follow it with the peel test: hold the tag in the air and compare.
Test the exact spot rather than the appliance. A metal door can have a plastic handle recess a few centimetres away that works perfectly.
What works instead
Move to a genuinely plastic part, which is free and often available within a hand's width.
Use an on metal tag, which is the reliable answer on a steel door and the one worth buying for anything permanent.
Mount on a small standoff, such as a plastic label holder or a magnetic badge holder that keeps the tag away from the surface. Note that this only helps if the tag itself is not against the metal.
Or move off the appliance entirely, onto an adjacent cupboard door or wall, which is often a better place to tap anyway.
Heat and cleaning
Appliances are wiped, sprayed and heated, and none of that is kind to an adhesive.
An oven front, a hob surround and the top of a fridge compressor housing all run warmer than the room, which shortens the life of an ordinary adhesive.
Kitchen surfaces are also cleaned with degreasers, which attack adhesives directly and lift tags at the corners.
For anything meant to last on an appliance, specify the adhesive for the temperature and the cleaning regime, not just for the surface material.
Frequently asked questions
Is a fridge door really metal?
Almost always steel with a finish on top. A magnet confirms it in a second, which is the quickest test available.
What about a plastic fronted fridge?
Some doors are genuinely plastic and many have metal behind. Test the actual spot rather than trusting the appearance.
Can I use a magnetic tag holder?
It keeps the tag away from the metal, which is the point, and the tag must not be sandwiched against the steel. Test the assembly before relying on it.
Will heat from the appliance damage the tag?
The adhesive gives out long before the chip does. Specify the adhesive for the actual surface temperature and the cleaning products used.