It’s anti-oxidant paste and is necessary at the connection of stranded aluminum wires to the lugs in an electric panel—as in the photo above—and also at any circuit breakers connected to stranded aluminum wires. Oxidation occurs over time at the unprotected surfaces of aluminum at wire connections. It is a process similar to the rust that builds up on steel and, although aluminum is an excellent electrical conductor, aluminum oxide is actually an insulator. 

    So, if left untreated, the oxidized surfaces of the aluminum wire impede the flow of electricity, which creates heat and can lead to an electrical fire. The paste is either black or gray, and should be used liberally at the connections.

    The series of photos in the video below shows graphically the overheating problem, with an overlay of an infrared camera image and a closeup of the oxidized wire at the breaker connection.

    Also, see our blog post What causes copper wires to turn green or black in an electric panel?

• • • • • • • • • • • • • • • • • • • • • • • • • • 

Here’s links to a collection of our other blog posts about ELECTRIC PANELS:

• What causes copper wires to turn green or black in an electric panel?  

• What is the maximum number of circuit breakers allowed in an electric panel?

• When should a corroded or damaged electric panel cabinet or disconnect box be replaced? 

• What is a tandem circuit breaker? 

• When did arc fault circuit interrupter (AFCI) breakers first become required?

• Can an electric panel be located in a closet? 

• Can an electric panel be located in a bathroom? 

• Can you add circuit breakers by different manufacturers to an electric panel if they fit?

• My circuit breaker won't reset. What's wrong?  

• What is a split bus electric panel?

• How do I identify a combination AFCI (CAFCI) circuit breaker? 

• What does a circuit breaker with a yellow or white test button indicate? 

• What is the maximum gap allowed between the front of a recessed electric panel box and the wall surface surrounding it? 

• What are the requirements for NM-cables entering an electric panel box?

• Why is a fuse box/panel an insurance problem for homebuyers? 

• Why is bundled wiring in an electric panel a defect?

• What is the maximum allowed height of a circuit breaker (OCPD) above the floor?

• What is the maximum height you can mount an electric panel above the floor? 

• What is the code required clearance in front of an electric panel?

• What is the main bonding jumper and where do it find it in an electric panel? 

   Visit our ELECTRIC PANELS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.