Introduction: How to "Weld" Aluminum Without a Welder

Using a propane torch and some aluminum brazing rods is a quick way to bonding aluminum without using a welder. It makes for a very strong bond and with a little practice can be done quickly with great looking results.

Step 1: Propane Torch

Picture of Propane Torch

The blue Bernzomatic will work just fine but I prefer using the yellow premium touch as it's hotter and works much quicker.

Step 2: Brazing Rods

Picture of Brazing Rods

You'll also need some aluminum brazing rods. I purchased all of these things at Home Depot.

Step 3: Cut Aluminum Tubing

Picture of Cut Aluminum Tubing

What I like about using aluminum is it's soft enough to cut with ordinary woodworking saw blades.

Step 4: Chamfer Edges

Picture of Chamfer Edges

I'll then chamfer the edges to allow a channel for the brazing material.

Step 5: Wire Brush Aluminum

Picture of Wire Brush Aluminum

Before brazing it's very important that the aluminum is clean.

Step 6: Heat Up Aluminum

Picture of Heat Up Aluminum

Clamp up the tubing and start heating the aluminum with a propane torch. Aluminum will start to melt at 1200deg Fahrenheit but the brazing rod will melt at around 700deg so we want to get the aluminum hot enough to melt the rod without melting the tubing. Getting the tubing hot enough may take 4 to 5 minutes. You'll know when it's hot enough when the rod starts to melt on contact.

Step 7: Braze the Aluminum

Picture of Braze the Aluminum

Rub the brazing rod along the channel until it's filled in and finish it off with some more heat. If you don't get the aluminum hot enough the brazing rod will just clump up and not stick to the tubing. This takes some patience and practice as my first few tries resulted in failures and ugly joints.


FredH65 (author)2017-06-17

I am not about being negative and certainly when 3 years or more late to the
discussion, but have my own opinions based on personal experience.

As some have commented there are now actual space age
adhesives which are stronger than brazing with cold joints that do not loose
molecular integrity. Heating to 1200 deg seems pretty extreme for setting
up a braze with dissimilar metals.

I have done much work using 4030 but mostly T6 as a local
Metal Supplier has all metals including DOM coming in 20 foot sheets and once
cut go to bins or sorted areas where the metal is sold by the pound, I believe
a 9 inch thick billet of T6 is originally like a sheet of plywood 4' x 8' heavy
as can be and about $9,000.00. I mostly use scraps from DOM tubing,
Angles and Drawn Shapes. Easily identified by filleted corners instead of
square in the inside, Obviously Tubing has no seams etc.. T6 is about
$2,00 per Lb. They sell a fantastic supply of race care pre-shaped
mounts, for Cage building. The best assortment of welding claiming
working tools ever. Have all kinds of pre-made parts for gates,
ornamental iron and 5lb Arc sticks in every type and thickness for 1/2 of
everyone else. Even perforated metal and honeycomb interior
structure that can be used for light weight aircraft walls or thick enough to
be used as a firewall if backed with material using the previously mentioned
Spacecraft Adhesives.

A note on Loctite, get and use them all in big bottles if you
can, also a silver paste called Anti Seize to be used on threads with
dissimilar metals, Wheel studs, spark plugs and everywhere you are not using
loctite., I had a High Performance Air cooled Baja Desert race bike and
besides flow porting and titanium valves the head was milled with a
groove. It is called O-ringing. No gasket, use Loctite O-ring head
sealing material specifically made for ultra high performance race engineering
at an astonishing price about $30 per oz and lay a bead in the groove.
Let it set and torque the head with the highest confidence, Compression
retention and Heat Transfer.

Back to T6. I am not equipped with gas shield or have
experience with said techniques. But found 4 simple steps to permanently,
solidly join aluminum that I can accomplish.

1. Keep the joint clean, and use a Stainless-steel wire brush that is only
for Aluminum ever, ever!

2. Clean the metal with what seems to be an Acid that sells for $10 at the
same Metal Supply. Clean of impurities joints is the most important.

3. Preheat the joint but not in excess using simple light always moving wide
focus torch to get everything even and not outside temp especially in cold of
winter. Not hot or anything much over 200 F.

4. I am a bad welder but there are white shielded welding electrode
sticks for Arc welders that look kind of like the Brazing rods but actually
penetrate and weld Aluminum. I have used them on 4030 and T6 specifically
to make a fuel tank mount in the bed of my truck that has been off road for 10
years banging around caring a 200 lb load with Zero issues on a 2 foot tall
structure with load factors of that amount of fuel moving against my hand built
frame. The Rods were from next door to Industrial Metal Supply at a
Miller Branded Welding Shop. Not cheap like Metal sticks but permanent.
With only 1 issue, I had not considered there is no real slag, just what
I see as the equivalent of Aluminum Oxide. Did not know until I kept
running into a Pro Chassis Builder Aluminum Oxide is the 2nd hardest material
and you will not be grinding it down with those never anything better on metal
work stacked sanding disks. I have to say with metal work, although they do not
flap and are marketed for use with angle grinders. The same Metal suppliers
have bulk packs made by Metabo. You can take down metal spatter and
unevenness without digging in, basically leaving a pre-finished surface.
Years ago, if I saw someone looking a grinding disks I would exclaim the unreal
benefits and long life of the sanding disks.

Now a little rub in although it has ended abruptly a few years ago,
with sale of the facility. There was a metal supply that dealt in scrap
near Temecula, I used to watch people complain about how little they were paid
for recycle beverage aluminum cans. All the while I am in the same room
buying Brand New Condition, Military Surplus hardware by the pound, $1.00 for
up to 25lbs. $0.75 to 50 lbs and continuing to $0.25 for 100 pounds (the
same cost as 25 pounds) for unlimited amounts of $68.00 Grease cups for spindle
lubrication at about $1.50 for 5 sets. Military Spec with data
sheets Stainless Steel hardware (at $0.25 per lb.) Bolts that are in
Cardboard Tubes. Screws that when ran into sheet metal of any type provided a
threaded connection grade 10 hardness, but had a reverse course thread pitch
under the head so the bolt can never back out without actually
tightening. Packaged Thrust Ball Bearings and seats, great for a windmill
to turn on. They had 12 mill poly Bags to keep all groups of hardware
sorted and unlimited 5 gallon pails to transport and keep forever.
While the Can people bitched, I was buying perforated steel sheet scrap for
$0.50 per lb. if you price it what I paid $12 for should have been just under
$200.00 and almost the same if I wanted less but made a cut at the Industrial
supplier. Originally this place sold scrap steel for $0.20 and $0.25
galvanized, but the all-time high ended up $0.40 and $0.50 for galvanized metal
in the non-Military area (this was actual scrap or remnants. I
purchased used largest shelving clearly from Home Depot and another set from
Lowe's which sold for $2.50 per foot for the uprights. My $16' tall 8'
wide shelves with locking supports was $120 and $140 respectively. Only
buying the triangular cross braces being lighter and sold at $0.40 by the lb.
made them $8 per, opting out of the heavy grids for platforms. That's my
unsolicited diatribe and I am attesting it is from personal experience and my
slanted perspective,

Nyxius (author)2016-01-04

I'd be worried about Bimetallic potentials and what that would do to corrode the aluminum. Anyone ever see what happens when you put aluminum and copper in contact with each other in water? I don't know what is in those soldering rods, but I'd feel pretty safe betting that it isn't aluminum.

imakeembetter (author)Nyxius2016-01-11

it's an aluminum zick alloy. there's no interatction, and the alloy actually dissolves some of the base al when brazing, it's an actual weld.

Nyxius (author)imakeembetter2016-01-11

If that is indeed the case, then it still is not a weld. No, it is a eutectic mixture. You are causing the aluminum to melt cooler by weakening the crystal matrix with the zinc. Not a weld. A true weld uses similar materials to yield a semi-continuous grain structure. Brazing ~= welding. Brazing == mechanical locking between differing grain structures. Welding is just a distortion of a continuous grain structure.

skysentinel. (author)Nyxius2017-04-16

The application of the finished joint/connection (environment, stress, load, temperature, etc.) is a primary consideration with this technique. That being said, I will respectfully summit in my humble opinion: If this process functions as intended, then the issue of whether it is a true weld or not, is of little concern to the average person, myself included.

imakeembetter (author)Nyxius2016-01-11

that's debatable, as the metallurgy of many weldments often different then the base structure, when filler is used, or a filler of a lower melting temperature is recommended or strongest, because of that debate welds are commonly defined as any process that melts, dissolves, or mechanically forms the base of two materials and joins them as one continuous material (with no mention of alloy) that is equal to or stronger then the base, thus making allowance for forge welding, friction stir welding(a process that can weld ti to fe), bimetal weldments(like this one), and plastic welding to be used in the same category and more importantly to allow all of the above to use the same set of standards with iso and astm, although the lower heat in this method does allow overlap with brazing and soldering, making this process notable, and largely debatable, however aluminum zinc alloys as a welding medium are compatible with many welding processes and are an excellent way to minimize distortion, and to create a stronger joint then the base structure, at the expense of ductility, therefore and considering the primary skill level this instructable seem to be catering to its a weld, and a good skill to have as well, because of the lower temps and therefore higher accuracy. fair warning however, don't use on a bicycle frame, the lower ductility will eventually cause failure. (although I believe firmly that any process that dissolves the base matrix should have its own category but it doesn't)

oh and welds have to be tempered to create a continuous crystalline structure.

hydranix (author)imakeembetter2016-12-11

In sorta layman's terms, a weld molecularly bonds the metals into a single joined piece. Melting a dissimilar metal between the two pieces is just a simple solder joint.

hydranix (author)Nyxius2016-12-11

Galvanic corrosion. A tiny piece of less noble metal, a sacrificial strip so-to-speak, in electrical contact with the metals you intend to protect will do just fine.

hydranix (author)2016-12-11

Butane can work but will be more expensive as you'll (quite a bit) use more gas to get the aluminum to melt.

Propane works and will be cheaper than butane, but still will require quite a bit of gas, unless you have an oxygen fed torch or a powerful air blown torch,

For a torch like in the picture (no oxygen or blower) you'll want to use MAPP gas (yellow can) as it burns much hotter and will melt the aluminum using far less gas and cost much less despite being a more expensive by weight.

amiir (author)2016-07-14

does butan torch works too? or we should use just propane?


dnorobo (author)2016-03-29

This is great - THANKS.

For alternative methods of metal joinery (and those looking for DIY/home tech aluminum joining options) I suggest the following (my experience includes exterior grade aluminum sign fabrication in a hurricane zone):

- acrylic adhesives (industrial grades are best - Lord Adhesives and 3M in the USA)

- double stick tapes (same)

- epoxies (various including above)

- mechanical fasteners (nut/bolt, angle iron, etc.). Also, thicker gauge aluminum can be tapped / threaded very nicely, allowing for mechanical screws to be mounted directly into the metal. The right hardware can be attractive.

- wire welding (equipment can be rented - ridiculously easy with right equipment)

Obviously, make sure you match your product's performance expectations to the fastening method's capacity. Make sure to read technical sheets, MSDS and fabrication guidelines, in order to make sure you use a product properly and to its fullest potential - most of that can be found online. If you are building something load bearing, that has moving parts, is for exterior use, etc. - you may want to consider consulting an engineer or accessing that knowledge.

imcp1024 (author)2016-01-31

good job, don't be afraid of cutting angles. gives wider bonding area, and looks nice. doesn't that cutting dull your blade?

Nightshade (author)2016-01-15

I for one appreciate your instructable. Don't let answering perfectionist keep you from doing what you do!! Keep it up Rick Morty would be proud.

Technoaussie (author)2016-01-01

Although I've always had a policy That if you can't say something nice about someone, say nothing, I feel the need to point out that a lot has changed since 'Aluminum solder first came on the market, soldering aluminum is not and never will be in any shape of form 'welding' aluminum. It is just a heat joining process that weakens the tensile strength of aluminum.

Many years ago I was one of the first professional boat builders in Australia to build a 15 ft boat completely free of any welding or riveting. It was 'glued' together and was rated to handle 65 horsepower outboards.

I was not the only builder converting to chemical joints but the size of the ovens needed and the unique jigs you had to build to hold it altogether during curing made them quite expensive.

Back to my reason for commenting... I supplied a 'kit' that would allow cold repairs to be made. This is what I'm writing about now. Soldering aluminum requires very accurate heat. How do you get this using a propane blow torch? With a crayon stick designed for the temperature specified to melt the solder. You put a crayon line near the solder point. when it disappears, you've reached the temperature.

Many aluminum suppliers and more advanced hardware outlets will sell you the low temperature 'solder' and heat indicating crayon in a package.

The bad part of using heat on aluminum is loss of tensile strength! The slower you cool it, the more strength it will retain but once heated to the point where you solder it, all sorts of often dramatic things can happen.

A much stronger and distortion free way to join aluminum is to 'glue' it together. The thermal setting adhesive used to equal the strength of aluminum itself is hard to find in DIY amounts and I doubt Mum would be very happy to find letterbox being bonded in her oven but there are plenty of 'cold bond' 2 pack adhesives on the shelves that will (when properly used) give you greater strength bonds with no likely hood of separation as solder joints provide.

TigerTom (author)Technoaussie2016-01-05

Which is the best "cold bond" 2 pack adhesives do you suggest to give me a greater strength bond with the aluminum i am bonding for a fence gate outdoors?

Technoaussie (author)TigerTom2016-01-05

Hi Tom,
If you can you tell me where in the universe you live it will help determine what is most suitable and where you can get it. The summer and winter temperature will help too. The people who supply me, tailor mixes to suit climates but they also have mixes for exterior use that can be mixed to be secure in below freezing or extreme humidity but unfortunately not one single mix for both climates.

I've got plenty myself I can probably give you some if you live in Australia. Sending it overseas can be a problem sometimes but I believe its available in most countries.

KROKKENOSTER (author)2015-12-31

This is what I looked for for longer that I care to remember Excellent!!

weldor (author)2015-09-03

For leaky rivets i an AL hull use 5200 by 3M. It is a polyurethane caulking designed for below the water line. Clean the area well with a non petroleum based solvent like denatured alcohol, mek, acetone, etc.
I have used it many times with great success on riveted seams. It comes in white, brown, and i believe gray as well. Once made an AL transom to replace the rotted wooden one by cutting aluminum plate (1/4 inch or 6mm). I drilled a series of holes and then put multiple plates together to equal the aprox 2 inches/50mm needed and then used 5200, stainless steel fasteners with the nylon lock nuts and fender washers to assemble it all. Did the leaky keel seem in 5200. Right over the old caulking. No leaks. Boat was from the 1950's.

elephantwalker (author)weldor2015-09-05

5200 is great stuff. As a boat carpenter I have used it on many occasions. There is a comparable product, pl by locktite, that, though not labeled for below water line use has passed my test for the use. Used as caulk or adhesive it is hard to beat and much more economical than 5200.

Please give us FULL details on WHICH ONE Loctite product is it... because "PL" is a large line of prducts that means "Professional Line"... There are many different products in the "PL" line...

weldor (author)amclaussen2015-12-30

I agree, loctite makes almost as many products as there are stars on the sky. The 3M 5200 comes in white, brown, gray, and i think black as well. Doe the Lotite come in different colors and is it paintable?

Ilan Voyager (author)weldor2015-09-04

You're right. It's in fact the best method for repairing riveted aluminum boats.

john.d.warner.9 (author)2015-09-03

Those sticks/rods are marketed in the UK (and elsewhere probably) as 'Lumiweld' kits.

They come with a Stainless Steel brush for cleaning the Aluminium, and a thin Stainless rod which is used to 'stir' the molten material during the process, which causes any impurities to come to the surface, rather than remain in the finished joint.

EXACTLY! The thing is to scrape the tenacious and elastic aluminium oxide "web" or membrane that immediately forms when the molten aluminum is exposed to the oxygen in the air. Thus, scraping the stainless steel brush will only remove some contaminants, but unless you "stir" the molten aluminium the molten material will not bond with the base metal. I believe that initial clenliness and specially scraping is the secret. Amclaussen.

There are plenty of brands, most with impossible claims and very high prices. The true price is around 20 US$ a pound, above it's a steal. We call that stuff flea market rods. Often the results are not reliable. Some serious houses like Kapp have good rods and a dedicated flux, thus making the zinc soldering easier and reliable. But you have to make a serious cleaning after as it may corrode hard.

In a lot of cases Tin Zinc alloy gives better results and it's more reliable as a flux is used. The tin zinc 85/15 wets far better so you can obtain a meniscus of solder each side of the tube's wall, dissolves and penetrates into the aluminum, is easier to finish and polishes nicely, and best of best it melts at 200-250° C so If you use the right torch, or a good electric gun you won't anneal the alu piece...Kapp has that at a very decent price and they sell at retail...

LarawayS (author)2015-09-03

Any suggestions on how to fix an aluminum boat? Just want the bottom all water tight. I used a marine grade epoxy to cover all the old seams. But I don't trust it. I've seen people use solder to fix their boats. But would it work well for aluminum? picture of the boat.

ChelseaM16 (author)LarawayS2015-12-29

I just repaired an 11ft tinny with major holes and cracks using 1.2mm and 1.6mm alloy patches (cut from a sheet of alloy bought @ a hardware shop) and marine silicon. cut the patch, roughen the area, drill holes for rivets (2.5 -3.5cm spacing) remove burs, cover with silicon, place patch, press hard, rivet. Works a treat - taken the boat in heavy seas at speed (hard impacts onto waves) with no leaks.

Ilan Voyager (author)LarawayS2015-09-03

Well prepared epoxy works very well and marine grade lasts a long. You can use also polyurethane as the 3M 5200. That thing glues ferociously, remains elastic so does not break and lasts years.

Welding is a pro task and wilh epoxy already in place it will be a pain.

devoalan (author)Ilan Voyager2015-09-08

well met, friend, well met. Your info on 5200 was very useful. I've used it for years, and had the horrible task of trying to remove it from wooden boats I used to restore, and once it "grows" into the wood, forget it. It is part of the wood. I just built a "bridge" or "gangplank from our back deck to the hurricane deck boat I have to use as a dock due to the government employees that need to justify their existence, and used the ISO brank to sister 2x6's to get the length I needed. Should work as expected.

devoalan (author)Ilan Voyager2015-09-07

HAve to agree with you on the 5200. That product, and if you want to get some at half the cost, the ISO brand urethane outdoor window caulk, which is the same formula, and a putty knife. Do all the rivets, and any cracks. It will be usable in a few hours, and will never leak there again. Want to join two pieces of wood together forever? soak the wood in water for a few hours, and then put this stuff on them and clamp. You will never get them apart or split that joint. you will break the lumber before the joint fails.and its totally weatherproof.

Ilan Voyager (author)devoalan2015-09-07

The 5200 and other polyurethane caulks dissolve very well with synthetic turpentine, that helps sometimes as primary to impregnate a powdery support as a concrete hole or for the cleaning or making nice fillets.

For gluing the wood, there is no need to wet it, and you may introduce stresses in the wood by swelling/drying. Pass simply a humid sponge, a light coat of "primary" (made of caulk and synthetic turpentine) to fill the grain, let it become tacky, apply the caulk and join. Best joints are about 0.3 mm thick, but when you want an elastic joint you can make thicker until 2 mm. Let cure several days vaporizing water if the weather if very dry.

Beware that polyurethane caulk may creep under permanent high stresses, and the joint may fail. Happens rarely in ordinary situations. That glues also very well metals and glass.

I do agree that in most cases a good structural construction polyurethane caulk with at least 35 % elasticity will do the job.

carlitosgy6 (author)Ilan Voyager2015-09-04

I can charge triple if a customer tried to fix a crack or a leak with epoxy, it mess up the weld plus i need to clean and clean and clean because is in every pore and crevice

kmcmorrow (author)Ilan Voyager2015-09-03

That's true. How to efficiently remove the epoxy that you think won't hold. Burning it off would have the EPA called.

tsturtevant (author)Ilan Voyager2015-09-03

Absolutely. Tuff to remove the epoxy cleanly. At this point we're approaching buying a different boat.

elephantwalker (author)LarawayS2015-09-05

I'd use a polyester fabric with a polyurethane caulk, pl/locktite poly caulk, on the seams. Just like the newer flat roof systems but better because of smaller area and the caulk is better than roofing compound. Caulk can be thined with paint thinner. Spread with a putty knife dipped in the thinner for a good surface. Maybe finish with a foam brush and thinnner to get a great surface. The epoxy should come right off with a heat gun and a putty knife. Power wire brush on a 4 in grinder with a bit more heat if needed will give you good clean surface to work on. I have used this caulk on shoes to make them really waterproof and it works very well indeed.

If you want a " back water" fix. Take a roll of 4 mill plastic. Lay out a strip the length of the boat. Put the boat on top of plastic and pull the plastic up to the gunnels and use spring clamps to hold in place. Trim plastic and carry to water. Won't leak.

kmcmorrow (author)LarawayS2015-09-03

Rent an inverter welding power source.

tsturtevant (author)LarawayS2015-09-03

Marine epoxy should be great. Surface prep and cleaning is the key G-Flex is great for this application.

Moose Dr (author)LarawayS2015-09-03

My sealant/glue of choice is JB Weld. You do have to make sure you clean/grind off the oxide, but I've never had JB Weld fail on me. I patch from the outside.

That said, on the next leak I'm going to try this method.

JonC3 (author)LarawayS2015-09-03

I have a similar aluminum boat. I had a small leak in the bottom and was not sure where it was located. I did some reading and watched some videos. My boat was on a trailer with motor attached. I filled the boat with water about 6 inches deep front to back. This will locate all the bottom drip/leaks. I marked where they were and drained the boat. I then used quicksteel to patch the holes and for good measure put silicone over the quicksteel after it hardened. I have no leaks now. If you follow the instructions, quicksteel works great. I have used it to stop up plastic holes with no water leaks. If you want to spend 5-10 times more money, they make really good stuff specifically for patching holes in aluminum boats. You have to get it from a marine dealer or order it.

P.S. If you try this be careful when draining or your boat might just stand straight up!!!

LarawayS (author)JonC32015-09-03

Thanks for the help bud.

Unity. (author)2015-09-06

This is a very poor way to weld.
A. There is no penetration in this method so strength & rigidity is going to be very poor.
B. There is no shielding so oxidisation is unavoidable thus making the join brittle and weak.

tpculp (author)Unity.2015-12-29

1) this is brazing not welding.
2) the coating on the rod is Flux which prevents oxidation.

Toms2782 (author)2015-12-29

what is the thickness of the aluminum. Wondering if it's solid enough to support a 2 10-gallon pots of liquid for home brewing as well as all the fitting for propane burners?

sbkenn (author)2015-12-29

The main problem with bonding to aluminium is that it oxidises almost immediately in air. Aluminium Oxide is extremely hard, nearly as hard as diamond, hence it being used for making sandpaper, but not good for bonding. Thistlebond make adhesives that do bond well to it though, some of it approved for repairing ship's fuel tanks ! Used with fibreglass, it makes a good repair. For an aluminium boat though, I suggest making an aluminium patch to cover the damage, bond using the aformentioned PU materials, then rivets or Self-tappers

Kevanf1 (author)2015-09-05

Rub some house hold soap (hand or face stuff that comes in a solid block) close but not in the area that is to be joined. When that turns black the aluminium should be hot enough to braze but not quite hot enough that it melts into a puddle... Always use a stainless steel wire brush never a mild steel one. A mild steel one can leave impurities in the metal preventing a good join. Nice Instructable, well done.

r6mace (author)Kevanf12015-11-14

nice tip! I'll try that.

alcurb (author)2015-09-21

Can this technique be used on aluminum mesh? The kind of mesh I'm speaking of is as delicate as window-screening. The mesh I have in mind is used for used for sculpting.

jimrittenour (author)2015-09-15

ugh. It might be easier to find another boat.

yrralguthrie (author)2015-09-03

I haven't done this, but all the demo's, my local welding supply house and youtube video's that I've seen note that a stainless steel wire brush must be used. There is a reaction between the aluminum and the stainless steel brush. These rods don't work otherwise.

About This Instructable




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