You’ve probably heard about a simple, cheap and universal method of welding aluminum with no expensive equipment required – only cheap propane torch and few aluminum welding rods. Does it really work and do you really need this product?
Please note here we are NOT talking about “true” aluminum rods that are used for TIG and oxygen-acetylene gas welding as a filler material. We discuss here low-temperature material used for “welding” in DIY and home projects. And call them “welding rods” or “aluminum welding rods” as manufacturers call them.
Read our article – we have collected together everything you need.
What the advertisement says
So, product description usually says about low temperature “aluminum welding rods”, sometimes they are also called soldering or brazing rods. These are used to make a sound joint between both thin and thick parts.
Melting point of aluminum is 1220 °F (660 °С). Aluminum welding rod’s working temperature is 720-750 °F 382-400 °С. Since no high heat is required, they can be used to build-up joints without discoloration and distortion.
Ads also say, that resulting joints are strong, have good electrical and thermal conductivity and corrosion resistance. One meter of 2.5 mm (~0.1”) diameter rods is enough for few meters of continuous joint. Using welding rods don’t require flux (but later we’ll discuss it) or fumes, making it even more easy.
Aluminum alloy of the rod is often stronger than aluminum you “weld” and it can be machined by milling, drilling, grinding. It allows you to weld aluminum alloys including siluminum and duralumin. Some say that steel (except stainless steel), and galvanized steel can be brazed with low temperature aluminum rods and resulting welds are stronger than the base material (as we will discuss later – this is mostly not the case). You can use welding rods to make a joint with dissimilar metals, for example aluminium and copper.
So, in ideal life, it’s the best and the easiest method of welding aluminium, “ideal for use” on repairs. Isn’t that a miracle?
No, basically not.
Are they a miracle? Nope!
All of these rods are made basically from aluminum and zinc. Some manufacturers advertises more metals that make together “revolutionary new alloy”. And maybe it’s a percent or two better. But I didn’t notice it 😊 The more zinc is added to alloy, the lower the melting point.
The “welding” you see in ads is not really welding. It’s brazing, actually it’s more like soldering then welding. Base aluminum does not melt, rod material does not penetrate the base metal, and the joint is much weaker than after TIG welding.
Yes, the material of the welding rod is usually stronger than the aluminum that you “weld”, but the key is adhesion to the base metal. And it is much weaker than rod alloy. They use a lot of tricks to fool you with a YouTube videos, but believe me, in this case, adhesion is a “weak link”.
I am also not sure about metallurgical match of the alloy to aluminum. The Zinc is more brittle, so the welding rod material is more brittle too, and the coefficients of expansion/contraction, fatigue strength, crack sensitivity also differ from aluminum.
Is this a scam? No!
Every technology has its value, features and limitations.
Technically using low temperature welding rods is not welding and even brazing. It is actually more like soldering. The alloy of the rod has a low melting point and it adheres to aluminum and non-ferrous metals.
- There is no need for expensive equipment.
- Due to low temperature you can “weld” thin metal, even soda can, as it is advertised.
- Flux is not required (but can and I think better to use it), and it won’t contaminate the inside of a radiator or evaporator.
- TIG or oxy acetylene cast aluminum welding often causes distortion and, for example, oil leakage under the cylinder block. Low temperature soldering doesn’t affect the base material
- Using low temperature aluminum rods have some benefits such as working with an area that may have corroded thru and it’s hard to be repaired by TIG weld
- Great for filling cracks, bullet holes, stone scratches on the boat bottom
- On complex surface of aluminum parts, TIG torch just pittes all the surrounding dimples and that can’t be tolerated. Aluminum welding rods and an oxy fuel, propane or mapp torch can be handful
- Everyone wants to use aluminum welding rod on applications that the original part failed and is seldom “stronger”. The truth is, that you should consider it more like a strong heat-on glue. The adhesion to base metal is not ideal and the joining is not really stronger than aluminum.
“True” TIG or oxy acetylene welding melts “true” aluminum rod AND base metal. Their molecules mutually penetrate from one material to another, and adhesion is very high. All applications associated with great forces, pressure of water or gas, structural elements, etc. which are important for your safety or money, must be welded by the professional welder
- If your “welding” fail, and you call TIG welder, he will have to grind the alloy completely to clean aluminum with a mill or carbide burr.
- Advertising says you can use any type of torch, in most cases propane one. But large application as a tank may require much heat due to large mass and area you are working. You could spend hours heating it and never get it hot enough. Use MAPP gas using aluminum welding rod on massive parts.
- You need to do some practice to obtain superb results. It will be easier for you if you know how to sold or weld
How to get appropriate result
1. Clean area down to base, brush the metal with steel brush till shiny. Do it really well. Oxidized layer on aluminum surface is an insurmountable barrier for aluminum welding rod.
2. Although the flux is not really needed, the result will be better, if it is used.
You need to find a soldering paste, matching temperature range, for example that one. It is soldering paste flux, that works in the range of 620-850 degrees, and can effectively dissolve the various metal oxides. Before welding, workpiece must be preheated to about 500 degrees and electrode coated with an appropriate amount of brazing flux.
If you don’t use flux (it’s OK), make sure you removed all aluminium oxide and meticulously cleaned the rods and the surfaces with acetone – just as for a high quality TIG weld.
3. Heat the area to be welded. Never apply heat directly to the rod, or the welded connection will be easily breakable. You have to practice and get the hand of when the aluminum is hot enough because aluminum does not change color when its heated like steel does.
4. Tin the surface. Rub the rod vigorously against the heated piece until the rod starts flowing. You have to scratch the tip of the aluminum brazing rod on the surface to break thru oxides. It won’t flow just by sticking the rod on the metal. Once more, you never want to heat the rod, just the metal. Heat the aluminium parts hot enough for the rod to flow without the aid of the flame, thoroughly tinning the surface.
5. Brush tinned surface under heat, thoroughly filling the open pores. This creates a film of rod over the weld or repair area, which aids bonding and strength to the weld.
6. With sides thoroughly tinned, flow in enough rod to fill the vee.
The most important aspects when using welding rods is to remember that you need to clean weld area from oxide film and contaminants, and use the heat from the parent material to melt the rod, NOT the torch flame!
Once more, with these rods you make rather soldering, than welding. But why not? Soldering gives excellent results over the centuries! It has been around forever. You just need to understand its limitations and make it right way.
I would not recommend it for things where structural integrity is important. Nothing that could take a sharp impact and I wouldn’t trust my life to them.
But you can produce joints strong enough for most of home purposes like furniture build and repair, aluminum windows, doors, gutters and siding. The joints do look nicer than welds, it is all about practice. If It’s not a critical repair, the stuff is cheap enough to try.