What is this?
Scorch marks or brown/black discolouration on a socket faceplate or plug are evidence of past or ongoing arcing and overheating. These marks are carbon deposits left by electrical arcing — the same process as an arc welder, happening in miniature inside your socket. The marks prove that dangerously high temperatures have occurred, and the fault may still be active.
Common causes
- Arcing at the plug-to-socket contact point due to worn socket contacts
- Loose terminal connections inside the socket generating arcing under load
- Repeated plugging and unplugging wearing down the socket contacts
- Overloaded socket causing excessive heat at the connections
- Short circuit or flashover across the socket face
- Moisture or contamination on the socket face causing tracking
Is it dangerous?
This is an emergency. Scorch marks are proof that arcing has already occurred. This means the socket or plug has experienced temperatures high enough to char or melt the material. The fault that caused the marks may still be present and could cause a fire at any time. Stop using the socket immediately and do not plug anything into it.
Can I fix it myself?
No. Do not use the socket. Do not attempt to clean or repair it. Turn off the circuit at the consumer unit if you can identify it. If the scorch marks are on a plug, do not use that plug or the appliance until both the plug and socket have been inspected. Call an emergency electrician.
When to call an electrician
Call an emergency electrician immediately. Scorch marks mean the socket has already reached dangerous temperatures. Even if the socket appears to work, the damage has weakened its integrity and it must be replaced. Do not delay.
What will an electrician do?
Isolate the circuit and remove the damaged socket
Inspect the wiring and back box for heat damage
Replace the socket with a new BS 1363 compliant socket outlet
Replace any heat-damaged cable or back box components
Test the circuit to ensure no further faults exist
Check other sockets on the ring circuit for similar issues
Typical cost
£70 – £200
Socket replacement is straightforward. If wiring behind the socket is heat-damaged and needs replacing, costs increase. Multiple damaged sockets will cost more.
