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Pinhole in corny, can i silver solder it?

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Beer666

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As the title says i have a pinhole in the bottom of a corny keg. I was told i could get it TIG welded but i cant find anyone around here to do it. Then i came across a video on soldering onto kettles.
Would this be an easy job that is likely to hold pressure? Advice welcome as apart from boards i have only ever soldered copper pipe. I have blowtorches already so hoping it can be a cheap fix.
 

dwhite60

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I'd trust a tig weld more than a silver solder especially in a pressure vessel. Weld is one with the base metal. Solder is a patch on the surface.
 

day_trippr

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If the breach isn't literally on the keg bottom necessitating removal of the rubber - so, somewhere on the sidewall - I wouldn't think twice about at least attempting to silver solder it closed. Then again as I've done some unrelated silver soldering I have everything needed, and I don't have a viable SS setup for my MIG welder - custom gas and SS wire needed, and back-shielding argon - way more complicated than silver solder...

Cheers!
 

apache_brew

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Similar sentiment here. I haven't done any silver soldering, but it doesn't hurt to try. The worst case is you still end up with a corny keg with a hole in it and beer spraying out. How big is the hole? How does a corny keg get a pin hole in it anyways?

Unless you find somebody who knows what their doing with a TIG machine, the wall thickness of a corny keg can turn a small hole into a big hole real fast.
 

Golddiggie

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IME, silver soldering requires higher temperatures than you can get from simple propane torches. IF you have an oxy/ace system, you could attempt it. I'd also NOT make this my first silver solder attempt. I also don't think I'd want to attempt this with a MIG setup (I have a MIG welder now, that I use for welding non-stainless steels). I have a TIG setup, but I'm pretty much a noob with that.

Check for a local trade school that offers welding. I'm sure the instructor could use this as a teaching opportunity for the class.

Keep in mind, welding (or even soldering) on something as thin as the keg walls is NOT the easiest. Kettle walls are significantly thicker in my experience.

Fortunately, I know someone that's an actual welder (by trade) that does almost everything with TIG. He's welded up several items for me over the years with solid results. Of course, I have yet to ask him to weld anything into a vessel that gets pressurized. BUT, I trust him to do it correctly when I [eventually] ask.
 

brewster2012

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I silver soldered a hairline crack in a weld in a conical fermenter that a co-worker gave me. It works just fine. I actually had to drill out the crack a bit to make it a pinhole in order to solder. I pressure transfer at lower pressures and it holds ok. I can't imagine such a small area of silver solder being problematic under normal keg pressure. Make sure you clean the area thoroughly, use the right flux and solder, and be patient with the heat. Moderate heat for a longer period of time over a larger area is better than intense heat in one area. Also, clean up afterwards with a water rinse (after the area is cooled to room temp) and Bar Keeper's Friend, followed by another rinse of water.
 

day_trippr

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Keg metal is wicked thin - gotta be close to or even under a millimeter thick - so even a propane torch will work fine with silver solder and appropriate flux...

Cheers!
 

Golddiggie

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Keg metal is wicked thin - gotta be close to or even under a millimeter thick - so even a propane torch will work fine with silver solder and appropriate flux...

Cheers!
I'd be very concerned over getting the stainless too hot before the solder flows. Since high purity silver solder has a much higher melting point than what you use with copper pipes.

Personally, IF any of my corny kegs developed a pin hole leak, I'd either take them for TIG welding, or bring them to the scrap yard (after removing any useful parts) and turn them in for scrap. Stainless steel usually gets you more per pound even these days. IF I was hard up for keeping the keg, either due to crazy pricing on new ones (many times what they are currently) or just not being able to get them, I'd take it for TIG welding.

It can be hard enough to weld into the walls for keggles. Those are significantly thicker material than corny kegs.

IF the OP does either method (TIG or silver solder), I'd do a serious pressure test of the keg long before trusting it. I'd go to several times the PSI it would be used at (if not close to the listed limit) and let it sit for several days to see IF it holds pressure (zero leaks). If it doesn't then it's to the scrap yard it goes.
 

day_trippr

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Well, I suppose everyone has their thresholds of concern, but imo considering the pressures most corny kegs experience in the hands of the typical home brewer the most likely negative outcome would be a dribble, not a nuke ;)

I'd definitely go for it...

Cheers!
 

Beermeister32

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Thin wall stainless will need to be tig welded not soldered. To do it right and then get the weld cleaned up on the inside of the keg isn't worth it. I say toss and go buy a new one.
 

RolandD

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You can silver solder stainless to itself or to brass or copper to make easier connections without risk of corrosion problems. The joint will only be as strong as the silver solder itself. You can use any silver solder, but you will need an acid-based flux specifically manufactured for nickel or stainless steel. Getting the steel hot enough presents the biggest problem, so be careful not to get it too hot, as it may cause surface oxides to form that reduce the quality of the stainless steel finish.
From: How to Silver Solder Stainless Steel

The main thing to remember is to heat the metal, not the solder. (My useless college degree is in Metalwork and Jewelry.) Mapp gas might be a better option than propane, but propane should do the job. Trying to silver solder it is a relatively cheap and easy solution. If it fails you can always get someone skilled to TIG weld it. Get some 'Hard' silver solder. It melts at a slightly higher temp, but will make a stronger repair.
 

day_trippr

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Meh. If this was a pinhole leak in a 1956 Ford F100 Panel Truck radiator or heater core I'd say throw a couple of tablespoons of pepper in the radiator and wait a few minutes :D
In this case, I'd give the solder a chance. It's a cheap shot to try, and no real harm if it doesn't work out - the TIG option would still be viable...

Cheers!
 

bad67z

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I‘ve spent my entire 25+ year carrier in the welding industry under the hood to start and in sales for the last couple decades. My first instinct is to purge/flood the keg with argon and tig weld it. Although the silver solder, as a first attempt is a very viable option. The challenge in my opinion would be cleaning up the backside of the repair, making sure the surface is smooth, and not a place to harbor “nastie”. This sounds like a pain in the ass to me.

That said used kegs at the moment (at least in my are) are not hard to come by in the $40-$60 range. If it were me I’d take the damaged one out of my rotation and replace it. I’d solder the damaged one and perhaps to store sanitizer or whatever in it.

It could work out but if you lost one brew, the cost of the ingredients and more importantly your time is far more expensive than the cost of a used keg.
 

Gnomebrewer

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If it's a tiny pinhole, a bit of food-grade silicon should seal it up. Anything bigger, put a SS rivet in first then silicon over it.
 

dwhite60

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I saw a fix on a water heater where they drilled the hole a bit bigger then used a stainless sheet metal screw and a rubber washer backed up with a stainless washer. For a quick temporary patch, it worked.
 
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Beer666

Beer666

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Thank you for all the replies really most appreciated. Really helpful. I think i paid £75 second hand for this keg as i could not find any new 12 lite kegs anywhere at the time. Would just forget about it but this is definitely the year of repairs and saving money for me after what seems like eternal lockdown.
No idea how it happened as it just emptied out one night and yes it is unfortunately on the bottom. I suppose soaking in really hot water might loosen the glue but i have not tried it.
I have tried to contact some local welders but no one has gotten back to me so might have a go with solder if i can first get the base off.
 
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