The original circuit breakers installed in our units, when the building was built in 1976, are made by Zinsco and do utilize an aluminum panel bus. Several websites indicate that there have been reports of some older Zinsco electrical panels and circuit breakers exhibiting arcing and contact point burning. The point of failure that was reported is the point of contact where the circuit breaker contacts clip onto the aluminum electrical panel bus.
As shown in the picture, the aluminum electrical panel bus is the two parallel metal bars at the top of the circuit breaker panel that the plastic circuit breaker units clip onto.
In order to determine whether our panels were in need of replacement, the board had an electrician disassemble and examine the panels in two units. The panels in both units were clean with no evidence of any corrosion, pitting or arcing. As can be seen in the picture, the aluminum panel buses are like new.
The electrician did advise that homeowners have the aluminum panel buses coated with a non-corrosive paste as a precautionary measure, the next time that they have an electrician working in their unit.