Using citric acid to condition stainless steel

[marmite]

One of my brewing mates reckons he has read somewhere about using citric acid to condition stainless steel. Has anyone else heard of this?

 

[CRoark]

Stainless will pit if exposed to an alkaline solution (do not use bleach on Stainless). To put the surface back to an acidic state you can use citric acid or any other acid to prevent corrosion. I use StarSan (either diluted or even just out of the bottle).

see http://beersmith.com/blog/2013/08/0...ion-with-jon-herskovits-beersmith-podcast-62/

 

[marmite]

Thanks that is just what I wanted

 

[Aleman]

Stainless steel will self passivate if exposed to air. It can be speeded up using an acid solution, For cleaning up welds then something like pickling paste is used (contains Nitric Acid), for general 'passivation' then any strong mineral acid can be used (sulphuric, hydrochloric, nitric, phosphoric). Weak organic acids while will work, it is not really any faster than leaving it exposed to air.

Stainless will pit if exposed to an alkaline solution

Actually not true, or not relevant, Murphys sell a wide range of caustic cleaners especially for stainless steel.

do not use bleach on Stainless

Again, not strictly a problem, chlorine corrosion is not an issue with the contact times and concentrations that are used in home brewing. if you are talking about permanent immersion in a chlorine solution (ie a swimming pool) then special steels tend to be used and even then corrosion will occur over quite a long timescale Murphys actually sell a chlorinated caustic product designed to be used on stainless steel.

As an experiment, I used a strong solution of Antiformin-S to clean out a corny, and I left it in there for a month with no sign of pitting even at the air/liquid interface.

Chloride corrosion of stainless steel is a real issue, especially at the gas/liquid interface where the concentration of chloride salts can be exceptionally high, and it is for this reason that thick bleaches (Where common salt is used as a thickener) should be avoided at high concentrations. Thin bleaches which don't have high chloride levels are perfectly safe to use.

 

[iwoo]

I work on a chemical plant and we passivate stainless with nitric acid then demin water, that is so we can use Hydrogen Peroxide, deffo not recommended for the home user, Citric Acid 10% is possible see herehttp://www.mmsonline.com/articles/how-to-passivate-stainless-steel-parts

for all the blurb, we still use nitric however.

 

[nobyipa]

pacifying stainless is mentioned in the how to brew by john palmer here


http://www.howtobrew.com/appendices/appendixB-1.html

you can use star san though
:drink: