Alloying
Definition
Incorporation of a foreign metal (steel, zinc, aluminium) into a copper arc bead. The arc's intense temperature fuses adjacent metals together. The specific alloy composition, readable by SEM-EDS, can confirm or rule out primary arc at a location.
- Mechanism
- Arc heat fuses adjacent metals
- Analytical method
- SEM-EDS elemental mapping
- Diagnostic use
- Confirm or exclude primary arc site
- Field
- Electrical fire failure analysis
Common questions
How does alloy composition distinguish a primary arc from a secondary one?+
A primary arc, which ignites the fire, tends to occur on relatively clean copper with alloying limited to whatever metal was directly adjacent, while a secondary arc formed during the fire can show alloying from a wider mix of melted building materials nearby. Comparing the elemental signature to the surrounding installation helps place the arc in the fire's timeline.
Is finding alloying alone enough to prove an arc caused the fire?+
No, alloying only shows that arcing occurred at that bead; it does not by itself establish whether the arc started the fire or resulted from fire damage to the wiring, so it is interpreted alongside circuit protection data and burn pattern evidence.
Related terms
- AFCI
- Arc-fault circuit interrupter. A device that detects the high-frequency signature of arcing current and opens the circuit. Required by the National Electrical...
- Arc Fault
- An unintended electrical discharge across a gap or through degraded insulation that releases energy as heat and light. Arc faults are classified...
- Notching
- A V-shaped or crescent-shaped indentation in copper at an arc site, caused by localised material ejection during the arc event. Notching on...
- Primary Arc
- An arc that preceded and caused the fire. Its markers on copper conductors appear before any fire damage has reached that location.
- Secondary Arc
- Arc damage created after a fire was already burning, caused by the fire melting insulation and shorting conductors. These markers are consequences...