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jebzter
12-17-2014, 11:30 AM
I received this keg back from one of our customers, it appears to have had something splashed on it while in their possession. I have never seen stainless fail like this, there are tons of pit marks, and longitudinal cracks in the metal. The kegs come from a reputable german manufacturer, I doubt it is a materials issue. Has anyone ever seen this before? What did you determine the problem to be? And what was the remedy?2096720968209692097020971

brewmaster 2011
12-17-2014, 11:33 AM
My First thought is that some one was cleaning the keg room or kegerator with bleach at about .5 gallons of bleach in a 5 gallon bucket.

TGTimm
12-17-2014, 03:04 PM
Wow. The pitting is probably--almost certainly--ferrous welding slag aka: birdsh... Someone was using your keg as a backdrop when welding (looks like wire-feed to me), then left it outside until the ferrous slag rusted away, taking some of the SS keg with it. As for the longitudinal crack, the only thing I've ever seen like that was caused by freezing hard while full of water/beer. Someone owes you a new keg, and/or goes on your "no sell" list. There is no remedy for your keg--scrap it.

TL Services
12-17-2014, 11:47 PM
I'd second TGT's suggestion of welding being the cause of this. Looking at the picture of the entire keg, you can see the way it's flowed from the weld source, which was quite close from the amount & severity of the marks. Also there appears to be a 'shadow' on the right side of the keg, so perhaps the workpiece was propped against it whilst it was being welded?

StandardKegs
12-18-2014, 03:32 AM
Hi Guys! Happy Holidays!

Contrary to popular belief stainless steel will rust, eventually.
Rust usually happens on the weld lines. The welding process rearrange the molecular make up of the metal in the weld line and this can make the metal more vulnerable to oxidation. looks to me whatever is on it the kegs have been there a while. but with proper passivization it should not be a problem....

The crack can be inherent problem from the form used to stretch the metal, somehow damaged. This can cause uneven stretch lines and cause cracking.
Thickness of the stainless steel is also very important, if it is not even, it will crack during the cooling and heating process.


How long did you own the keg? How long did your client hold this keg?

Cheers!

Zhi
Standard Kegs
www.Standardkegs.com

liammckenna
12-18-2014, 10:17 AM
Looks like some sort of metal or acid splash combined perhaps with freezing the keg.

Pax

liam

Bainbridge
12-18-2014, 10:30 AM
Looks more like a Lost Deposit to me.

jebzter
12-18-2014, 01:02 PM
we think we've got it nailed down to bleach being splashed on, along with what is called stress corrosion cracking. What happened to our kegs seems to fit the description of that type of damage. Keg was held by the bar for 2 weeks, we have had it for a few months. We re-passivate all our stainless prior to first use, typically acids wont corrode the stainless like that.

MikeS
12-18-2014, 01:18 PM
I was thinking welding slag, too. That's the only thing I've ever seen that makes stainless look like that. (Or maybe someone used a grinder to cut some mild steel near it?) EXCEPT..... welding slag would have burned through the plastic tape keg wrap. The fact that there is no burn through on the wrap suggests, indeed, some liquid splashing on it. But holy moley, that's some serious liquid that can do that! Bleach doing that within a two week span? Color me skeptical. Very interested to hear any more developments!

Cheers- Mike

TL Services
12-18-2014, 01:43 PM
I'd be very surprised if that is the result of hypochlorite from bleach for several reasons:

1. Hypochlorite tends to result in quite irregular crevice corrosion, whereas this looks too regular;
2. Surely if the keg had been splashed, then there would be obvious signs of the liquid running down the keg?
3. There is no difference in the corrosion on the main material and welds, which seems unlikely, unless the kegs have been very well passivated.

For some more info on crevice corrosion: http://www.ssina.com/corrosion/crevice-pitting.html

However, I take the point that the band appears untouched so, if it is corrosion rather than welding slag, then coupled with the extensive cracks, I'd be concerned about the quality of manufacture.

GlacierBrewing
12-18-2014, 04:02 PM
Being a Montana brewery, I'm going with someone thought it would be fun to shoot the pressurized keg with a shotgun!

my two cents.....

Prost!

brewmaster 2011
12-18-2014, 05:06 PM
I'd be very surprised if that is the result of hypochlorite from bleach for several reasons:

1. Hypochlorite tends to result in quite irregular crevice corrosion, whereas this looks too regular;
2. Surely if the keg had been splashed, then there would be obvious signs of the liquid running down the keg?
3. There is no difference in the corrosion on the main material and welds, which seems unlikely, unless the kegs have been very well passivated.

For some more info on crevice corrosion: http://www.ssina.com/corrosion/crevice-pitting.html

However, I take the point that the band appears untouched so, if it is corrosion rather than welding slag, then coupled with the extensive cracks, I'd be concerned about the quality of manufacture.

Unless Sodium Hypochlorite was atomized in a spray bottle.

gitchegumee
12-19-2014, 12:07 AM
Intergranular Stress Crack Corrosion on a susceptible material requires:
1) Halogen
2) Tensile Stress
3) Elevated Temperature
Don't know if that is what you have, but the cracks are in the highest tensile stress area. And that is where the grain boundaries would line up during the ironing process that makes the keg half. Seems to be no difference in corrosion process between the base metal and the weld. Normally, I don't think IGSCC would attack 300 series on a weld as the base material is usually austenitic and the weld is usually martensitic--unless post-treated. I would not believe it is IGSCC unless there is some definitive proof. Great project for a technical school or university troubleshooting class. Teri Fahrendorf used to ask for examples of unusual failures to teach a class. Hang on to this one in case someone can diagnose it--I'd love to hear what did the deed!

TL Services
12-19-2014, 12:16 AM
Most over-the-counter bleach is around 5% sodium hypochlorite, so I guess if someone was spraying neat bleach onto a hot keg it might have happened that way...although there is something slightly Darwinian about the thought of someone doing just that!

lhall
12-19-2014, 06:17 AM
I'm going with the shotgun theory too.

MikeS
12-19-2014, 08:01 AM
Maybe some kind of manufacturing defect accelerated by being sprayed with something?

As an experiment, try peeling back the keg wrap and inspecting for anything curious underneath. Try masking off a spot and spraying it with bleach and see if anything happens.

Regardless, weird...

-Mike

GlacierBrewing
12-19-2014, 09:55 AM
Being a Montana brewery, I'm going with someone thought it would be fun to shoot the pressurized keg with a shotgun!

my two cents.....

Prost!

hmmmmm......if the keg tape/wrap was on the keg when this "event" happened and due to the fact the tape does not show pitting, I may have to retract my shotgun hypothesis.

Dave

TGTimm
12-19-2014, 10:16 AM
... kinda throws a monkey-wrench in my welding splatter theory, too. Sure looks just like welding splatter on SS, 'though, something I've accidentally (or ignorantly) done myself.

dick murton
12-20-2014, 03:42 AM
I would also go with chloride induced corrosion - hypochorite splashes being capable of such corrosion, especially if the quality of the stainless is now good "303" as one person recently put it regarding much Chinese stainless. I have certainly seen full depth pitting and stress corrosion cracking from dried up residues of terminal sterilant in flat bottomed vessels, and on other occasions, from fittings in soakbaths.

The stress cracks are probably simply as a result of inbuilt stresses during manufacturing. Realistically, who passivates the outside of kegs? I know I washed the outside of some chinese kit recently with nitric as a quick and dirty passivation (the insides and fittings were fully passivated with hot acid), but that was just becasue it was already rusting!!

As has already been said - lost deposit at least, better still, a full reclaim for cost of brand new keg.

StandardKegs
12-21-2014, 11:02 PM
for the most part Chinese manufacturers are using 304 stainless with a 3 hr passivization process. So this should not have happened if it was a corrosion by of damage.

My kegs are require to be tested with bleach and salt solutions to judge corrosion resistance? Who were your kegs from? I know you said it was a German company. Ask them how thick was your oxidation layer. Standards are around 65MN, my kegs are around 75MN.

stress cracks can happen if the form used to stretch the top n half kegs has any deformity to it. or if they did not use the correct lubrication causing uneven stretching.