stainless steel oxidation ?

[lari]

hi all,
i have a ss ball valve which i tried to clean thoroughly with some bar keepers friend. long story short i left parts of ss valve soaking in bkf solution for a few days and its now almost black, dar greyish colour and smells a bit ‘metaly’. i assume its some kind of iron oxidation or something. any ideas?
picture: left dodgy, right normal.

 

[augiedoggy]

Maybe it had some sort of chromium coating that the BKF effected... I wasnt even aware it was practice to soak stuff in a BKF solution... I believe its meant for manual cleaning since its a mild abrasive

looks like the same damage as here in this other thread...

https://www.homebrewtalk.com/showthread.php?t=582772

both star san and BKF are acid based...