Possible Beer Stone in Fermentor

[Davy6Mac]

Hi All,
Just need some advice, have recently noticed on the inside of my Brewmonk 30L Conical Fermentor a slight rough section all the way around the inside,
it’s roughly around about where the Krausen would be when fermentation is taking place. I always clean using a microfibre cloth and Chemclean before and after fermentation, then it’s thoroughly sanitised using Chemsan. Read a few articles and was wondering if anybody else on the forum had experienced anything similar, from what I have read could it be Beer Stone. Don,t have any pics as can only feel the rough section.

 

[SMP Brewery]

Had to google Beer Stone and found this.

https://www.morebeer.com/articles/removing_preventing_beerstone
Basically they say try vinegar if it is.

 

[MrJay83]

Is this an example of it? Only on the lower end of my thermowell. Tried a bit of bar keepers friend and it's really tough. The pic below is after a few minutes of rubbing it in.
It's a bit hard to see but the surface texture changes just before the table meets the wall.