110.12(B) Integrity of Electrical Equipment and Connections.
Internal parts of electrical equipment, including busbars, wiring terminals, insulators, and other surfaces, shall not be damaged or contaminated by foreign materials such as paint, plaster, cleaners, abrasives, or corrosive residues. There shall be no damaged parts that may adversely affect safe operation or mechanical strength of the equipment such as parts that are broken; bent; cut; or deteriorated by corrosion, chemical action, or overheating.
If you are going by the letter of the law, then you've already committed yourself to replacing the panels according to the part highlighted in red.
BTW, green Scotch Brite is no more abrasive than fine steel wool. If you think the Scotch Brite is excluded, then you must exclude all steel wool as well. And all metal polishing agents like Brasso or even red rouge (as a polish is nothing more than a very very fine abrasive). In fact, the blue Scotch Brite, while not containing any embedded abrasive grit, does have a scrubbing action by virtue of its polymer fibers. How shall we define abrasive?
I think the key to section 110.12(B) is the part I highlighted in blue. Now we have to decide and define what is considered "damaged".
The issue with sewer gas is the sulphur, which can cause whiskers to develop.
Expansive growth of silver whiskers has been found on primary current conductors of circuit breakers in switchgear at pulp recycling mill. The major environmental factor to initiate the growth is relatively low concentration of Hydrogen Sulfide (H2S). As soon as a thick enough layer of silver sulfide has been formed, metal filaments start to grow virtually everywhere but most intensely in locations usually having elevated temperature while electrical units are energized. Just in two months after previous cleaning, the whisker grows up to several inches (6-8 cm) long and up to 0.04 in (1 mm) thick. Most of the whiskers are made of silver with 1-3 % of copper. The surface of the whiskers long exposed to atmosphere is contaminated with silver sulfide. The growth eventually leads to catastrophic thermal failure.
Would Aluminum Buss be resistant to the H2S/Wiskers? I noticed in the pictures that the neutral bar looks pretty good.
It is even a real problem? The black color may not be an issue, it may have about the same conductivity as the original copper.
I'm still trying to figure out how your two panels got exposed to such a high-concentration of sewer gases. Did decide to turn a porta-potty into a storage locker?