The Good, The Bad, The Ugly: A Welding primer for homebrew

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After seeing many threads on this topic I've decided to chime and give my two cents about welding.
I am a professional welder, NOT a professional writer. Every time I see pictures of these welds posted in these forums I cringe and would be embarrassed to put my name on them. I know more than most but not ALL, so for you experienced welders out there, feel free to nit pick me at the end!
Let's get started. First off, what does a good weld look like and what does a bad weld look like?
Well, if it is clean and the same color as the base metal (your pot/fittings etc) inside and out
that's a good start. If the weld bead is pleasing to the eye inside and out,your on the right track.Personally I like a bead that looks like what we call a "stack of dimes."

It should be uniform and the word of the day is: CONSISTENT.
Consistency is biggest problem I see everyday at the shop I work in. If you have thirty fittings welded to the same kettle, or thirty different kettles, they should all look the same.
This is not a guarantee nor prerequisite, but it shows an experienced hand welded your product.A weld that looks really bad probably is,but not necessarily. CWI's (certified weld inspector say every day..."just because a weld looks bad, doesn't mean it is." And that is true for structural steel and the like. But what we're dealing with here, in my opinion, if it looks bad it is.
Now a large part of these discussions include bits about purging or back-purging. They are the same thing. Back purging is exactly that, purging the back side of the weld with a gas equal to the shielding gas running through the welder. There are several gases and mixtures used for stainless steels and vary by application, method, and sometimes welder preference. I will only talk about pure Argon and GTAW (TiG) process because GMAW(MiG) and FCAW(flux core) have no business near your pots and kettles, PERIOD.
The following example is not stainless steel, but shows how simple and easy (read wrong if your weld shop does not do) back purging can be, plus look at the nice, CONSISTENT weld bead.

For large pots and kettles, a bit foil or cardboard fitted over the top with a purge hose taped through a hole will suffice. I recommend 10 CFM for the purge line. Argon is heavier than air so where ever it naturally vents out of the set up should not be the lowest point. It should push air out, not suck it in.
If you notice any dark gray "sugaring" or crystallized look to the inside or non-welded side of the joint...

You are looking at an incorrect and non-sanitary weld. If say, a pipe is welded, two pieces end to end and you look down inside and it looks just like the outside, as if it was actually welded on the inside as well, it was properly back purged. The following shows both purged and non. The bead in the foreground is purged, the latter is not...

It may be not so easy, depending on application to get back-purging to specific areas. There are other means such as purge blocks:

Other things to be considered are equally important for sound, quality sanitary weld.
The weld side of the bead also must be taken care of in regards to the shielding gas. Under no circumstance should the HAZ(heat affected zone) be exposed to ambient air when it is above 800F. Technique and machine settings can take care of this. Basically, travel speed should be low enough that the metal loses the cherry red before you travel half the diameter of the Tig torch cup. Or weld a distance equal to half the diameter of the cup and stop, allowing "Post flow" ( a machine setting that allows gas to be expelled for
a preset amount of time after the arc is terminated) to cool and keep the weld shielded. Other equipment such a trail shields are use. They leave gas behind as the torch progresses forward...

Their are also several styles and types of cups used on Tig torches. If a "gas lens":

is NOT used, I would definitely use the trail shield, however I do not recommend welding without the lens. Gas flow is greatly controlled and focused for that CONSISTENT clean weld.

Above on the left is flow with a lens, on the right is without. The difference is clear and speaks for itself.
If your weld shop doesn't mention any of these techniques or equipment or you don't see them in their shop,they better have one of these...

A glove box can eliminate all of the above mentioned equipment but is a bit more difficult for most welders to use because it greatly reduces maneuverability and welder's hand stability. Other terms you might mention or inquire about when at your weld shop could be DCEN( DC electrode negative) or "straight" polarity.
Proper tungsten electrodes should include:
  • Yellow=Lanthanated (multipurpose and most common)
  • Red=Thoriated /
  • Gray=Ceriated.
These are all alloys of tungsten and all are usable, however I would recommend them in the order of red,yellow, then gray. Gray being the least used. Your shop will probably say yellow.
The welder should wear "doctor exam" gloves when handling clean parts and welding rod. Parts should be cleaned with NON-metallic scrubbies and if they need be ground, grind with new fresh abrasive pads/wheels etc that have not been used. Used pads could have been used on carbon (ferrous) steel or even picked up bits from dirt
and dust containing them. A quick wipe down with acetone and lint free rag after grinding or scrubbing prior to welding is a good bet. Wipe down the welding rod as well. Even the oils on your hands can contaminate a weld area and cause porosity and other rejectable defects.After welding, the area should be cleaned well, inside and out.
Some talk of "passivation" has floated around here as well. Passivation is simple really. It is the removal (in stainless steel) of ferrous metal particles from the surface of the affected area, to inhibit rust. There are several chemical treatments that involve strong acids and temperature controls.These methods usually deal with machined parts of aerospace components
and electrical devices. For our purposes and thankfully the cheapest yet still effective method, is the clean method.Chances are, if the weld has been cleaned already, using the NON-metallic scrubbie and no discoloration is present, it is naturally passivated. Scrubbing removes the softer ferrous particles and the oxides (discoloration) and leaves the harder, purer, higher chromium content of the alloy on the surface and the instant these parts of the alloy are exposed to free oxygen in the air, they oxidize forming the hardest layer of highest chromium content material.
This should leave your kettle virtually rust/corrosion free!


@T_Baggins In your opinion, what do you think welders should charge for 1" and 1.5" items being welded in a keggle?
I'll second jflongo's question.
@T_Baggins what should an average charge for a TiG weld cost? I know that prices will vary from one place to the other. But when I called some local places around here (Kansas City) I got prices up to and including $600. When I told the guy I only paid $137 for my 20 gallon pot he just said well...probably not a good idea to weld it then. Sigh.
@Marc77 I just talked to someone in my area. They said they charge $30 for 1/2" fittings when I emailed them, so $90 for the 3 I want welded in. Here is their original craigslist post.
This is a great article about TIG (GTAW) welding, but you can also use stick (SMAW), MIG (GMAW) and flux-core (FCAW) to weld stainless. I am not positive, but I think if the back is open, then you still need to back purge.
GMAW/mig SMAW/stick FCAW/flux core CAN be used to weld stainless steel, but they are more for structural weldments and heavier gauge material than what we're dealing with here.
And who wants weld splatter/BB's all over their kettle? I sure as hell don't! Flux core SS is about $400 a spool, so Thtphtphpt!!! Anything other than Tig will pop and spatter which leaves greater chance for porosity or inclusions in the weld, and that's not sanitary at all. Sure you could pay for the extra grinding and have your pot look like **** and possibly trap in unwanted scummies and crap you don't want.
$30 bucks/fitting seems reasonable. I would estimate most shops to average $60/hr or so. So half that for what I could do in 30 min or less...not bad. And I don't see the need for the pricing to change for a range of sizes from 1/2 to 2 inches. Even though a 2 inch fitting is 4 times the size of a 1/2 fitting and takes 4 times the filler rod, it shouldn't take more than 1 rod typically.
First let me say I work in fabrication though I don't do welding, but I had my buddy TIG weld my fittings into my kettle. Even though I mentioned to him about back gassing it when I gave it to him, he didn't end up doing it. The back side is somewhat rough looking with slight rust tint. Although I could clean it up with a dotco and chemically passivate it, I don't like the idea of those chemicals inside the kettle regardless of how well I could rinse it. To the point, is the term "sanitary" that is thrown around in this subject referring more to the cleanliness of the bead or the actual sanitation (health concerns) with the weld? It seems to me that it would not really cause a notable health issue.
@kylerbills Sanitary weld refers to it's use, as in food handling equipment and such. A weld that is not up to spec for sanitary conditions can be a hazard in that bacteria and other biologicals can be embedded in the weld and spread contamination to anything that comes in contact with it. If the weld had been back purged and sanitarily welded, simply cleaning the area with a dry scrubbie to the point of removing all discoloration would allow it to naturally passivate.
All that makes sense but in when discussing kettles, everything is boiled and brought up to temp inside. It just seems negligible aside from a small possibility of corrosion getting into the wort (if it got out of control).
That may be true, but a shitty weld on ANY thing is still a shitty weld. And that's fact not opinion. There is no debate here on or about whether or not a sanitary weld is required for brewing equipment or not,nor it's safety. The deal here is to inform John Q Brewer on how to identify quality work and not pay for junk. I work hard for my dollar, don't you?
I'm not trying to argue the fact that back gassing is more sanitary, just wondering if its even worth considering redoing the fittings for something on my scale and not for sale to the public. No debate from me that it bugs the hell out of me looking at it, but its a pain to redo it. Personally, if I'm fab'ing something, I won't let it go out the door if it looks like crap.
Well, I guess it's truly in the eye of the beholder! Maybe not redo what you have, but consider another venue when upgrading.
Well, I guess it's truly in the eye of the beholder! Maybe not redo what you have, but consider another venue when upgrading.
Great article! Its also worth mentioning the importance of the size of tungsten, the added benefit of using a make shift heat-sink and a back stepping method so that your HAZ in minimal. There are also GTAW power sources with pulsed frequency to minimize heat input if you have the cash.
This is perfect. Nice job man. I do have a question tho,
I flipped my keggle and filled it with helium at 10cfm or so when I welded my fitting to the bottom/side but I still got oxidation/pickleing on the inside.
Does helium not act as a shielding gas? I thought that it was working well by staying in the upside down kettle. I tested it out by flipping it right side up and a bunch of gas came flying out of there like a big wind (kinda cool...).
Great article the only thing I could add is the 2% thorated green tungsten 1/16" is what I used for 20 years welding for food service companies like Nestle, Frito Lay , etc. A simple coffee can stuffed with steel wool makes an excellent purge can, if you have a bad weld you do not have to live with it. Take it in to be dry washed" and back welded stainless is very forgiving, and can easily be repaired again and again.
@heapyjeepy you will have color change regardless, I've never used helium my self and I tend to associate it wit older aluminum welding methods, but I see no reason that i should not have worked just fine.
@T_Baggins it wasn't so much the discoloring i was concerned about but the "sugaring" like your 3rd picture. My boss (my welding teacher) at my old machine shop called it pickling.
Kudos! Good info to put out there for the laymen. My only critiques would be, a little more stress on(any tool used on cres alloys must not have been used on any other material prior),and stating cfm for backpurge instead of resistance to flow. I always liked to have 1-2 inches showing on a manometer when purging. Too much pressure concaves the weld and will get a undercut rejection from the NDI's, but that's nitpicking.
@jeepy, as for the helium I have used it for aluminum and as part of a 3 gas mix for a specialty wire. I don't know the science behind it, I think it has to do with ionising, but it allows for greater heat transfer of the arc. "Hotter arc" as it's commonly referred to. I have only known of argon and nitrogen being used for purge, regardless of the shield gas used, so maybe it doesn't behave the same when not in the presence of an arc.
@heapyjeepy OIC, I didn't realize that's what you meant. Interesting, I'm not sure why it shouldn't have worked the same as argon. As far as I knew the goal was to keep oxygen out of the equation. Depending on the joint type, shape etc... a simple block of metal laid flat and tight up to the back side of the weld area will suffice in some cases, maybe not for specific sanitary conditions...but well enough to prevent sugaring.
Awesome article. Now I will have to source a gas lens.
My old Miller Dialarc also needs some help. The arc wanders before finally settling down. Back purge is an absolute must!
Excellent article. I don't know the first thing about any of this stuff but now I know what to look for and ask for with regards to anyone I might have work on my equipment. Thanks for the great write up.