Recently, I had problems with a pinkish/orange-colored bacteria (Serratia marcescens) in my bathroom. The bacteria would show up in my shower and sink, specifically near or around the drains. To counter the bacteria, I bought some mold and mildew remover which contains bleach.
This seems to have soundly defeated the bacteria, but has unexpectedly led to a new problem. Unfortunately, some form of black mold has appeared around my shower drain.
I thought this would be a good challenge for the mold and mildew remover. After spraying and letting it sit, when I tried to wipe away the mold, it left black streaks across the shower floor which were very hard to clean off.
I wanted to make sure this black stuff (whatever it is) was gone for good, so I sprayed an excessive amount of the mold and mildew remover and let it sit without wiping away. To my surprise, the black stuff came back stronger than ever (the picture above).
I think it is unlikely that I have found some sort of super mold that feeds off of bleach, which leads me to believe that letting a bleach-based cleaner sit on my drain has somehow caused it to corrode.
If it is corrosion, how should I go about cleaning it and treating my drain so it doesn't happen in the future? If it is something else, what are my options for taking care of it?