Discoloration on ungrounded bus normal?

As you can see there is some discoloration on the ungrounded bus. I’m thinking this isn’t a concern but wanted to get others opinions(maybe something manufacture related). I did not see any form of damage, just discolored. I have seen a few like this lately but most are crystal clean.


I have seen this on panel bus too and IMO unless there are other indications of a problem it’s perfectly normal.


Maybe it is anodized?

I notice it more on panels coming out of Mexico. They do not rinse the parts enough after Tin plating


Yep, I see this often and agree with the others that it’s not a problem. I talked with a knowledgeable electrician about this once and he seemed to think it had to do with the way the metal was finished and that it’s something heat-related (prior to the panel being installed/used).