I got some from Tesco to make sure all is well with my cornie - is there anything I should know before using it?
Active ingredient is sodium hypochlorite
Baby's sterilising fluid
I don't have one but aren't cornies stainless?
Beware oxidising biocides and stainless steel.
Even John Palmer a metallurgist who writes good books on brewing but thinks there is lead in brass got this right.
clicky
Beware oxidising biocides and stainless steel.
Even John Palmer a metallurgist who writes good books on brewing but thinks there is lead in brass got this right.
clicky
Fair comment - it's added at up to 3.5% to improve machinability. But the way Palmer has written it it implies that all brass has lead in it.DaaB wrote:(and fwiw i'm pretty sure there is lead in brass fittings which aren't used in potable water supplies, we had a good link posted here regarding the work of WRAS and brass fittings).
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Graham
I do wonder if scare-stories about bleach and stainless is another thing that we are OTT on with regard to home brewing. Again, I think that we (We being everybody else except me) have taken something that might be an issue within a different industry and applied it to home brewing without regard to the process.
True that all halogens are reactive to stainless and so are chlorides. Standard bleach, being a combination of both, makes it more reactive than most. Iodine is also a halogen, but we hear no cautions about using iodophor.
Indeed, Iodine is far more corrosive to copper and brass than bleach is to stainless (it leaches the copper out and converts it to copper iodide), yet we hear of people happily using iodophor on their shiny breweries with brass fittings and copper pipe, but would put their hands up in horror at using bleach on stainless.
I would say that bleach is not a problem in the concentrations that we use it, even strong concentrations. If the passivation layer gets stripped off, so what? We are not using our vessels for anything aggressive, and the acidic nature of beer will (probably) instantly re-passivate the surface. Most acids will repassivate, including citric, so I assume beer will do the same thing.
The welds are rarely stainless anyway. The constituents of stainless all melt at different temperatures, so the weld has lost its properties and does not passivate in the same way. In any stainless thingy, it is the welds that first show problems.
Commercial breweries are stainless and they use bleach, or other chlorine donors, to sterilise. Beer pumps are stainless, yet beer-line cleaner is bleach, with no warnings about corrosion possibilities.
True that all halogens are reactive to stainless and so are chlorides. Standard bleach, being a combination of both, makes it more reactive than most. Iodine is also a halogen, but we hear no cautions about using iodophor.
Indeed, Iodine is far more corrosive to copper and brass than bleach is to stainless (it leaches the copper out and converts it to copper iodide), yet we hear of people happily using iodophor on their shiny breweries with brass fittings and copper pipe, but would put their hands up in horror at using bleach on stainless.
I would say that bleach is not a problem in the concentrations that we use it, even strong concentrations. If the passivation layer gets stripped off, so what? We are not using our vessels for anything aggressive, and the acidic nature of beer will (probably) instantly re-passivate the surface. Most acids will repassivate, including citric, so I assume beer will do the same thing.
The welds are rarely stainless anyway. The constituents of stainless all melt at different temperatures, so the weld has lost its properties and does not passivate in the same way. In any stainless thingy, it is the welds that first show problems.
Commercial breweries are stainless and they use bleach, or other chlorine donors, to sterilise. Beer pumps are stainless, yet beer-line cleaner is bleach, with no warnings about corrosion possibilities.
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Vossy1
I think the reaction between iodine and copper should be made a sticky along with others, some do's and dont, even if only best practice.Indeed, Iodine is far more corrosive to copper and brass than bleach is to stainless (it leaches the copper out and converts it to copper iodide), yet we hear of people happily using iodophor on their shiny breweries with brass fittings and copper pipe, but would put their hands up in horror at using bleach on stainless.
Anyone should be wary when a sanitiser changes colour on contact with a material in such a short space of time, as iodophor does with copper
Last edited by Vossy1 on Mon Jan 21, 2008 10:15 pm, edited 1 time in total.
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steve_flack
I use antiformin on my corni kegs but I keep the contact time down to around 30 minutes by which time it's removed all the gunk in the keg. I then rinse really well.
I don't use antiformin on my conical though - it's a bit more expensive if I've got this wrong
In the 'don't use X on Y' category also comes peracetic on copper. In fact copper is crap with everything. Even starsan seems to react with copper if you leave it to dry.
I don't use antiformin on my conical though - it's a bit more expensive if I've got this wrong
In the 'don't use X on Y' category also comes peracetic on copper. In fact copper is crap with everything. Even starsan seems to react with copper if you leave it to dry.
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Graham
I wonder if the pitting in this instance is caused when they take the things out of the bath, and the the stuff runs into globules and concentrates under evaporation. Stainless doesn't wet very well so it naturally forms into globules. I think something electrolytic goes on under these circumstances.Daab wrote:the Hop Back keep their stainless fittings etc in what appears to be a horse trough filled with a dilute sodium hydrochlorite solution, the fittings are I saw in there were pitted but when they are around 1/4" thick it doesn't really matter.
My guess is, and it's only a guess, is that it might be okay while submerged in the solution. The reason I say this that there is a case history somewhere on the Interweb about a swimming pool that has stainless "furniture", barriers, door handles and the like, and they are all corroding - wet hands I guess. But the stainless pool ladders that are made by the same company, from the same grade of stainless, but totally submerged in the pool are totally unaffected.
There is also an issue with machined items in as much as cutting-tool particles get embedded in the surface and the electrolytic action thereby enhances the dissimilar metals corrosion thingy and causes pitting. It is probably a good idea to use only the green 3M type scrubbies on stainless and not metal ones - not even stainless scrubbies.
I say not stainless because I once left a wet stainless scrubbie on my kitchen drainer over a weekend and both rusted. Okay, it was only superficial and easily removed by simply rubbing with a finger, but it illustrates a point that even stainless on stainless isn't immune to this sort of thing.
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steve_flack
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Graham
This will at least explain why globules (like water on a polished car) are significant - you have an air, metal and solution interface all at once.steve_flack wrote:I remember reading somewhere the main problem with bleach and stainless occurs at the junction between the solution and air. This of course may be untrue.
Mind you, although interesting, our low concentrations and low dwell times mean that it is probably not relevant to home brewing.
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Graham
DaaB wrote:http://www.amteccorrosion.co.uk/papers/ ... steel.htmlPitting Corrosion of Stainless Steels
The most usual type of localised corrosion attack on stainless steel which results in perforation of tanks, vessels and pipe walls is pitting corrosion. It takes the form of small diameter but deep holes. These are usually less than 1mm in diameter and can penetrate many millimetres into the metal.
The pits are the anodes in the corrosion reaction and the remainder of the surface is the cathode. Pits initiate at defects in the protective oxide layer, or passive layer, on the surface. Commonly, these defects are inclusions that form from impurities, such as sulphur, in the steel. These impurities can result in very local depletion of the alloying elements, thereby preventing the protective oxide from being totally uniform.
The conditions that lead to pitting are moderately high temperatures, high concentrations of chloride ions (from salt), other halides such as fluorides, bromides and iodides. Acidic conditions (low pH) also aid the growth of the pits, which are themselves acidic.
This acidity within the pit is the reason why pits can continue to grow once they have been initiated.
Makes you wonder why they ever use stainless - doesn't it?
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AT
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Graham