Mini Keg Discussion / Mods / Show Off - Dedicated Thread

[wide eyed and legless]

Good penetration, shame about the pickling, does explain the mystery of the black beer, the acidity of the beer is pickling the weld, either send them back (I would do this) or make up a solution of citric acid and pickle.

Are these are the mini kegs bound for Australia.

 

[Zorco]

Again, a call for perspective..

We've bought each keg for a few tens of dollars and still have no facts on any risks.

The representative from the stainless steel industry called me yesterday, but I was getting home from the CBD.

I'll try and speak with him today.

 

[Coalminer]

WEAL can you give details of pickling with citric acid? solution strength, times etc?

 

[Jack of all biers]

It has been provided elsewhere. I think it was MHB. 120 gm/L citric acid up at around 70C for 10 mins or 30 min at room temp. Rinse and leave to dry passivate for a few days. This would be for a standard passivation, but with those welds I'd be checking them first prior to letting it dry. To be honest though, I'd be at least letting your retailer know about it as there may be lots of customers effected who aren't following this thread.

 

[trhr]

WEAL can you give details of pickling with citric acid? solution strength, times etc?

If they're as bad as some of my kegs, there's a few steps.
They really need a SS commercial cleaner to remove the impurities, then some pickling bath fluid needs to diluted and poured into the keg, then I'd do the same with a passivation chemical to be sure. Then whatever cleaning process is required afterwards.

As said before, I run a construction business which specialises in steel fab and do some SS, but hardly any food grade work. So I won't bother trying, instead when I have time I'll drop them off to my SS pipe/tank welding friends to fix in exchange for some brew.

This all should have been done before we got the kegs. Im combination with the faulty regs, I'm feeling pretty underwhelmed.

I may one day try them again, but for now I'm going back to 9L kegs and growlers.

 

[wide eyed and legless]

What Redman says is correct, if the pickling has been missed then what's to saY the degreasing which is the operation prior to pickling wasn't missed also,
the acid will not remove any manufacturing oils. The safest way is to use the citric acid but it does need to be heated to around 55 to 60 degrees C I believe
You will probably find something in Google

 

[Grott]

It would seem everyone but WEAL ignored my post #671. Just saying in a friendly way.

 

[wide eyed and legless]

You made the right call there grott, hard to believe that the pickling would be missed. I have used hydrofluoric acid before on brazed joints very effective and quick but not very nice to use.

 

[Dae Tripper]

Were they all from the same purchase?

Yes, same purchase.

 

[Dae Tripper]

Ok so I am going to let some people know the difference between pickling and passivation as currently I disagree with using citric acid to pickle, yet it is a useful passivation acid, I could be wrong though.

Waiting for a mate I emailed last night with the photos as he is a bit of a stainless guru.


Pickling

Pickling is the removal of any high temperature scale and any adjacent low chromium layer of metal from the surface of stainless steel by chemical means.

Where the steel has been heated by welding, heat treatments or other means, to the point where a coloured oxide layer can be seen, there is a chromium depleted layer on the surface of the steel underneath the oxide layer. The lower chromium content gives lower corrosion resistance. To restore the best corrosion resistant performance, the damaged metal layer must be removed, exposing a fully alloyed stainless steel surface. Mechanical removal may leave abrasive or other particles embedded (interfering with corrosion performance) or may be impractical, so chemical means are usually employed.

Procedures incorporating pickling solutions of nitric (HNO3) and hydrofluoric (HF) acids remove the scale and the underlying chromium depleted layer and restore the corrosion resistance. Pickling solutions also remove contaminants such as ferrous and ferric oxide particles. Pickling solutions other than mixtures of nitric and hydrofluoric acids exist and can be used for specialised applications.

Pickling pastes, where the solution is mixed with an inert carrier, are commonly used to treat selected areas such as welds.

Pickling involves metal removal and a change or dulling in the visual brightness of the metal.

Electropolishing is a useful alternative to pickling. Metal removal is achieved, but usually results in a bright, smooth and more highly corrosion resistant finish.

Passivation

Passivation is the treatment of the surface of stainless steels, often with acid solutions (or pastes), to remove contaminants and promote the formation of the passive film on a freshly created surface (e.g. through grinding, machining or mechanical damage).

Common passivation treatments include nitric acid (HNO3) solutions or pastes which will clean the steel surface of free iron contaminants. Care must be taken in selecting and using passivation treatments to ensure the selected treatment will target the contaminant. Passivation will also aid in the rapid development of the passive oxide film on the steel's surface. Passivation does not usually result in a marked change in appearance of the steel surface.

Both pickling and passivation solutions can employ dangerous acids that can damage both the operator and the environment if not handled correctly. Stainless pickling acids are highly corrosive to carbon steel.

It is essential that all acids are thoroughly removed by rinsing the component after completing the process. Residual hydrofluoric acid will initiate pitting corrosion.

It may be advantageous to neutralise the acid with an alkali before the rinsing step.

 

[wide eyed and legless]

Yes, that's similar to what grott posted on post 671, citric acid may do it or it may not, that is why I suggested a return, the beer seemed to be pickling the kegs so the citric acid could work, I wouldn't want to advise anyone to go down the hydrofluoric acid route.

 

[malt junkie]

I wouldn't think the average Joe would have much luck with paste either considering the inaccessible location of the welds. I'm still to check mine.

 

[Zorco]

Alright, I don't see any compelling link between untreated Stainless welds and the black rice juice.

But the presence of chromium oxide is a concern

https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdbterm+@DOCNO+1619

 

[Dae Tripper]

The beer isn't a pickle, and it is reacting with the metal.

As above, the oxide layer can be seen, there is a chromium depleted layer on the surface of the steel. The lower chromium content gives lower corrosion resistance.

Basically it would be like putting beer into an iron keg.

Does anyone have a dud keg for me to inspect? I am going from Singleton to Gosford tomorrow morning so I could swing by.

 

[peteru]

I don't see any compelling link between untreated Stainless welds and the black rice juice.

I do. The poor welds are corroding and the rice rubs off the corroded layer much better than water alone. That also implies that as long as there is poor quality surface at and around the welds, corrosion will continue and the blackening will recur with time as the "rust" builds up.

But the presence of chromium oxide is a concern

Based on that paper, I wouldn't be any more concerned about it than I was before. The corrosion of the minikegs is a concern, but I don't think that there is any reason at all to single out chromium oxide.

My pragmatic take on this problem is that this is a manufacturing and quality control issue. The process was poorly executed. It should have been caught by QC and would have been trivial to fix at the factory - just send the minikegs through an electropolishing bath again and re-passivate. Now that the minikegs have been delivered to customers, remedying the problem is cost prohibitive. Imagine the overheads involved in collecting all the kegs and shipping them back to the factory or to a local business that can do this!

The most practical way to get those minikegs into a usable state would be to come up with a simple enough process that we could use at home to fix them. I am thinking along the lines of a poor mans home made electropolishing setup. Fill keg with appropriate acid solution (something accessible, like citric acid would be best), insert an electrode made of appropriate material through the opening at top and hook up to a battery for x hours. I think we need to get Lyrebird_Cycles involved in this topic - I suspect he'd have a pretty good idea of where to start...

 

[Zorco]

Agree we need an expert to correctly draw conclusion between the welds and the blackening - if any

Nope, not only considering chromium oxide, just the first evidence I've found that there is a health risk.


Your conclusion above has no merit. They do, however, make a good hypothesis. We'll get there I'm sure. I hope I don't get to throwing out all my kegs...

 

[Zorco]

OK, I've spoken with an industry expert and here are my notes.


- It is possible that the stainless steel may be a 200 grade which has a larger manganese component
1: We are going to cut a keg apart and send a sample to an analysis lab for a spectro test

2: We are to look inside a brand new keg and see that it hasn't been pickled

Health concerns part
- In food and very much so for beer, iron dissolving in only a few parts per million can be detected and is unplesant
- Chromium oxide has been extensively studied looking for leaching. On first use some acidic foods like rhubarb and tomatoes can show small levels of chromium oxide but a hot wash would clean new stainless
-On the surface of the steel there is only a few nanometres of chromium oxide and it stays there, even unpickled weld areas. On the surface it is not Chromium6 which is known to be carcinogenic. It is Chromium3 with no evidence of health concerns; it exists in a relationship with a hydroxide.

Then I asked what could cause the black
It may be the iron as there are oxides of iron that are black. Anyone with a black film can try to use a strong magnet and it should stick. Some sulphides are black and he looked in his chemistry handbook while I was on the phone and checked that there are oxides of manganese which are black.

8We can send a sample to Spectrometer Services. An estimate of cost would be $150 for a simple sample.
https://www.google.com.au/webhp?sourceid=chrome-instant&rlz=1C1CHBD_en-gbAU720AU720&ion=1&espv=2&ie=UTF-8#q=spectrometer+services&*


So where to from here....

Finding a keg to destroy will be simple enough and I think it should be Peteru's or Batz's. As this may have serious outcomes, I'll speak with Mark about providing some/all of the testing fee.

We should also try and replicate the 'blackness' and see if it is magnetic... Peteru, I think that should be in your court.

- I'm leaning towards being happy that whatever is going on, it is safe for consumption - though undesirable.
- I'm also fairly confident that these can first be viewed as manufacturing errors and those who have a problem should get a replacement from Mark immediately.


I've got more to say but need to get lunch before a meeting.

Catch yas!

 

[Parks]

Well the magnet test show interesting results.

My ex hard rive magnet sticks like this:
My 2 iKegger growlers stick hard on the body but only very lightly on the cone.
My "The beer can" 4 L mini keg does not stick on the body but sticks hard on the cone.

So seems like they have 2 different grades on stainless used?

 

[GoodDuck]

It might be interesting to see what happens if you stick a magnet in the Black Rice Juice

 

[mstrelan]

This would have been perfect for me to test if it was a few hours earlier. I left my glass of black rice juice to settle and decanted of the rice water part. I then let that settle again and decanted it off so there was about a quarter teaspoon of pure blackness. It was quite thick and I suspect would have been magnetic. Unfortunately I tipped it down the sink thinking it was not useful.