Breaker

[Tom Rees]

Should I be concerned about the white substance at this breaker, what causes it? It is a 60 amp breaker feeding a panel next to it (less than a foot away).

[paul hardy]

That appears to the filler (sometimes ceramic) that is installed over the adjustment screws at the factory.

[Billy Stephens]

That appears to the filler (sometimes ceramic) that is installed over the adjustment screws at the factory.
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Or Sanchem NOOXID electrical grease & electrically conductive grease dielectric grease and contact lubricants (http://www.sanchem.com/aSpecialE.html)
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[Rollie Meyers]

Seems to be a common occurance of Gould/ITE, ITE Siemens breakers in a damp location. I would not get too worked up about it.