Stainless pitting in G40

[YeastFace]

Brewed yesterday and did my normal cleaning regime - alkaline cleaner (sodium metasilicate) soak for about an hour, then a rinse with water, then a rinse with starsan.

After pumping out the alkaline cleaner, I had a load of these white spots. I though this might just rinse away but they are not deposits and seem to be in the metal. They are all around the same height in the unit, which is higher than the cleaner volume will have reached.

Will passivating the stainless get rid of them?

 

[peebee]

"Passivating", as in an "acid wash", possibly. Try Bar Keeper's Friend, which may (or not!) move the marks, "B.K.F." is based on Oxalic Acid...

"Passivating", as in "passivating" stainless steel, possibly not, or it won't be "passivating" at any rate! "Passivating" is a spontaneous action after you've cleaned off surface impurities like iron leaving the chromium that's in the stainless steel to oxidise on the surface and protect it. The action of preparing a surface to "passivate" is basically selective "etching" ... the title of this thread suggests "pitting" which "etching" certainly won't remove!

Good luck with the Bar Keepers Friend, it's pretty good at removing stains and marks which is probably what you've got ... not "pitting". This is "pitting"!

https://www.thehomebrewforum.co.uk/threads/black-marks-on-stainless.101066/post-1189105

 

[YeastFace]

Thanks.

 

[MashBag]

Try Bar Keeper's Friend, which may (or not!) move the marks, "B.K.F." is based on Oxalic Acid...

I would do that too. First

 

[lmbollinger]

Bon Ami powder cleaner. Similar to bar keepers friend, but gentler on your skin (and environment). If you believe the link below, at least: Bon Ami vs. Bar Keepers Friend (Test Results) - Prudent Reviews

 

[LeeH]

Bon Ami powder cleaner. Similar to bar keepers friend, but gentler on your skin (and environment). If you believe the link below, at least: Bon Ami vs. Bar Keepers Friend (Test Results) - Prudent Reviews

But how will that passivate stainless?

 

[peebee]

But how will that passivate stainless?

I had to look that one up because I'd heard BKF didn't "passivate" either...

First off: Bom Ami won't because it's alkaline and won't dissolve iron impurities.

BKF is acidic and will remove traces of iron from the surface of stainless steel. BFK is not recommended for use on iron or any surface for more than a minute, so presumably it is "etching"? The BKF Website even has articles on passivating brewing kit by a very excitable chappie (apparently, if you don't do it your beer will go off! ). But it can't be very effective.


But there are acids that will do the whole job of passivating (news to me, I always insist the acid only etches away the surface in preparation for natural passivation). Nitric Acid is a strong oxidiser and will do both jobs (clean/etch and oxidise):
https://diversey.com/en/blog/how-pa...d chemical,activate the chromium oxide layer.
Plenty of homebrew forum posts on the subject of "why bother for what difference it makes". Even from the States where they do tend to be a bit keen on performing such over-zealous procedures.

 

[JockyBrewer]

Those could be spots from where you've added water treatment acid and it's splashed on the sides. I've got quite a few on my brew kit going back years. It's never gone any further than those spots, and doesn't seem to clean off permanently whatever I do.

 

[MashBag]

Those could be spots from where you've added water treatment acid and it's splashed on the sides. I've got quite a few on my brew kit going back years. It's never gone any further than those spots, and doesn't seem to clean off permanently whatever I do.

Do you throw it in from the other side of the room