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Watching a seasoned and experienced welder join two pieces of metal is almost like magic. A little electricity, some specialized equipment, and a touch of artistry can turn two distinct pieces of metal into one single entity as if they were never two pieces. Doing this with steel is one thing. Doing it with aluminum is an entirely different work of magic.
How Good Are Aluminum Welding Rods? Advances in metallurgy and welding equipment have made it possible to achieve satisfactory welds in most grades of aluminum using specialized aluminum welding rods without the need for special welding equipment such as MIG or TIG.
Aluminum welding rods work exactly like the rods used to weld other metals.
Aluminum has a much lower melting temperature than mild steel. Compensating for the low melting point of aluminum requires different settings on the welding equipment and different types of welding rods.
Aluminum alloys vary enough in their density, strength, and melting temperature that the type of welding rod used can vary depending on the aluminum alloy involved.
Matching the type of welding rod to the aluminum alloy is just the first part of the puzzle.
Using the right settings on the welding equipment is the third side of the triangle. Get all three parts of the equation right and things begin to work.
Aluminum Welding Rods are Good, if . . .
Aluminum welding rods are considered filler material.
When welding two pieces of metal, either with a torch or with an electrical current, the aluminum welding rod melts to fuse the two pieces of metal.
It is a relatively simple process provided some basic rules are followed, especially with aluminum.
Don’t try to join dissimilar materials. Attempting to weld two different alloys of aluminum can be frustrating at best and a total disaster at worst.
Use the proper welding rod. The welding rod you chose must be the proper material to fuse with the alloy of aluminum you are welding.
Use the proper settings on your equipment. For electrical arc welding, the proper current and amp settings are essential to achieve the proper heat range.
If you are gas welding, experience in working with aluminum is critical to be able to judge the way the metal is reacting.
By and large, aluminum welding rods are the same.
The major difference between the manufacturer’s products is the coatings that may be applied to the rods to aid in the welding process or the actual material used in the rod.
Aluminum welding with rods is possible and can achieve satisfactory results, sometimes even superior results, when done properly.
As an example, the author of this link gives a detailed technical explanation of the process he used to arc weld aluminum including some videos of the process
All Aluminum Is Not Created Equal
Pure aluminum conducts electricity well and electrical components are the common use of 1XXX aluminum. Aluminum alloys are designed for specific applications based on tensile strength, corrosion resistance and its ability to be heat treatable.
These specific formulations lead to special problems when trying to weld aluminum alloys.
A four-digit number designates the categories of aluminum alloys. The first digit of that number is an indicator of the alloying metal used.
There are currently eight different classifications.
The chart below shows the eight classifications, the principal alloying metal and some information about welding this alloy of aluminum.
|Principle Alloying Element
|Description and Notes
|99.9% pure Aluminum Weldable with 1100 filler metal
|Weldable but prone to cracking Use 2319 or 4043
|Easily weldable using 4043 or 5356 filler metal
|Weldable and also the base for many welding filler materials
|Easily welded with 5356, 5183 or 5556 material
|Magnesium and Silicon
|Cracks easily at high temperatures. Use 4043 or 5356 filler material
|Generally not used for welding.
Information courtesy of Clinton Aluminum
What Kind of Aluminum Do I Have?
The trick for most hobby and home metal workers is to figure out what alloy of aluminum with which you are working?
Many hobby metal workers end up with a hodge-podge of various scraps and end cuts of metal they want to use in small projects.
Lay two pieces of aluminum on a workbench, and you soon realize that it is next to impossible to figure out what alloy of aluminum you have.
There is no real and practical way to tell what alloy of aluminum you have by examining the metal.
Short of laboratory analysis, without any documentation on the metal itself, you cannot make that sort of judgment with any confidence.
The best strategy for dealing with an unknown sample of aluminum is to make the parts for your projects from the same piece of scrap.
Cutting all your parts from the same scrap of aluminum ensures that you are, at the least, dealing with the same alloy of aluminum. It does not help you to choose the type of welding rod to use.
The only method for choosing a welding rod is to make some welds using what you believe to be the best rod and check the quality of the welds.
Buying end cuts and scraps from a professional welding shop is another approach. Welding shops may organize their scraps by alloy.
They face the same challenge in identifying scraps.
Keeping their scraps and end cuts organized properly allows them to make use of these pieces more efficiently. Many welding shops will sell off-cuts at a reasonable price.
What Kind of Welder Do You Need for Aluminum Welding?
What do you have? Do you have a torch or a stick welder? What type of repair or project do you want to do?
As with any job or project, be it working with wood or metal, matching the tool to the job is essential to success.
Gas Welding Aluminum
Gas welding aluminum requires a torch capable of bringing the aluminum stock to the correct temperature to fuse the welding rod and the metal. The two most common types of gas welding torches in use for this process are oxyacetylene and oxyhydrogen.
The downside to welding aluminum with gas and a welding rod is the aluminum tends to dissipate the heat from the torch so rapidly that it is difficult to keep the material hot enough to create a proper weld.
There are several techniques for judging the temperature of the metal as the torch is applied to ensure that the aluminum is hot enough and stays hot enough as you weld.
Metal temperature ranges can be estimated using the following methods.
Char Test – A pine stick is rubbed over the metal. When the aluminum is at the proper temperature, the pine stick will begin to char. A darker char indicates a higher temperature.
Carpenter’s chalk – Mark the area to be welded with carpenter’s chalk. The chalk line will begin to turn white when the aluminum is hot enough to weld.
Hammer test – Using a metal shop hammer, tap the metal lightly near the point you are pre-heating. As the metal reaches the correct temperature, the metal will lose its ring.
Carburizing Test – Adding a thin layer of soot to aluminum allows you to judge the temperature as you pre-heat the aluminum. The soot will disappear as the proper temperature at the proper temperature. This disappearing act occurs at approximately 300 degrees Fahrenheit.
CAUTION: Don’t coat areas that have been fluxed. The soot can be absorbed into the weld and may cause bubbles in the weld.
For a more detailed discussion about gas welding aluminum check out the Weld Guru
Arc Welding Aluminum
Arc welding, or stick welding, is a process that uses an electrical current to provide the heat to fuse two pieces of metal. The equipment produces high heat and extremely bright light.
CAUTION: Use extreme care when arc welding. Not only are you using extremely high electrical amperages, but you are also producing high heat and extremely bright light that can cause serious damage to your eyes. NEVER look at an arc weld being made without proper eye protection.
Enough electrical current is created between metal and the welding stick to create an electrical arc between the two.
This arc provided the heat to melt both the metal to be joined and the welding rod that provides the filler material to form the weld.
Arc welding is an extremely efficient form of welding and is used in many fabrication shops today.
The problem with arc welding aluminum is the very low temperature at which aluminum melts and its ability to dissipate that temperature rapidly.
These two properties of aluminum often cause the aluminum to burn away the material. This burning can leave large gaps or bubbles in the welds.
Properly adjusting the settings on your welder is one of the keys to stick welding aluminum.
The other is your approach and technique. Using the proper welding rod for the aluminum alloy you are welding.
Minimizing the time the arc is in contact with the metal will make stick welding aluminum much more effective for the home or hobby welder.
There have been recent advances in welding rod manufacturers that have made it easier for home, hobby, and small shop welders to achieve better results with stick welders and aluminum construction.
Some of these rods are designed to be used with DC Arc welders, which are usually found in home and hobby shops. For more information about one of the companies manufacturing specialty aluminum welding rods, visit the website for Zena Corporation.
Making the Right Choice
So, how do you know what welding rod to choose ? There are some things you should consider when choosing the proper aluminum welding rod for your project.
Know what you are working with. – Know the alloy of the aluminum you want to weld. Understanding the alloy makes the selection of the rod almost automatic.
There are numerous charts and guides online to help you match the proper welding rod to the aluminum alloy with which you are working.
As an example, this chart provided by AlcoTec is excellent.
Know your welding equipment – Different styles of welding equipment require different welding rods, especially with aluminum.
The manufacturer of your welding equipment is the best source of information on how to set up your welding equipment, especially Arc welders, for various types of metal, welding rods, and applications.
Understand the differences in the types of welds that you need to produce – Are you welding butt joints or right angles? Will you be welding overhead or running vertical welds as opposed to horizontal welds?
Some aluminum welding rods are not suitable for overhead work, so adjust your rod selection to match the application.
The Miller welding company has much more detailed information about welding rod selection on their website here.
Before You Use Aluminum Welding Rods
Having the right tools, the right welding rods, and the right settings will only go so far if you haven’t done the right things before you start to weld.
The best aluminum welding rod in the business is only as good as the preparation you do to the surfaces you are going to weld.
Starting your welds on aluminum with dirty or contaminated surfaces will almost always result in poor results. Aluminum, when exposed to the atmosphere, develops a tough outer layer of oxides.
This oxidation layer can prevent the aluminum from heating properly and from flowing easily to mix with the filler material from the aluminum welding rod.
Contaminants on the aluminum can mix with the aluminum and the filler material creating a poorly formed weld that can often crack or bubble.
Some contaminants will cause spatter during the welding, which can damage the surface of your aluminum material some distance from the weld area.
There are some things you should do before starting any aluminum welding.
Clean the areas to be welded with a solvent to remove any surface contamination, especially any type of oil or grease. The solvent you use may leave contaminants.
Avoid some hydro-carbon based solvents such as paint thinner or lacquer thinner. Acetone, MEK and toluene are all good solvents to use.
Use a wire brush grinder to remove any paint or other coatings and to remove any oxidation from the surfaces to be welded.
When making cuts on your aluminum material, use a high-speed saw or plasma cutter.
Some alloys of aluminum will require that welded edges are milled or ground to a beveled shape before welding.
Weld quickly after cleaning – Aluminum will start to re-oxidize almost immediately after being cleaned. Aluminum will develop enough new oxidation, if left too long in the open, to affect the welds.
Are Aluminum Welding Rods Really Good?
Yes, aluminum welding rods are really good. The caveat that follows that answer is the same one that goes with almost anything else in the market place. Buyer beware.
Buy from reputable dealers and reputable manufacturers. Aluminum welding rods are only as good as the material in them, and the quality controls in place during manufacture.
As with almost anything, there are products on the market that don’t meet specifications and will not produce quality results.
If you buy quality, known aluminum welding rods and follow the proper techniques, then you should be able to produce sound welds in your aluminum materials with equipment that is available relatively inexpensively for most home and hobby metalworking projects.
We would offer a few other suggestions to those who are interested in welding aluminum.
Many local community and junior colleges offer welding classes. By and large, these classes are not budget busters and offer an excellent opportunity for learning proper techniques and developing sound skills from knowledgeable instructors.
We highly recommend these programs.
Provided you make good decisions when buying your aluminum welding rods and you have at least a basic knowledge of aluminum welding techniques, you should have a better than average chance of successfully welding aluminum.
As with any skill, you can study, read, and observe, but until you put your hands on the equipment and material, your skills will not develop and sharpen.
Get some aluminum scraps, buy some different aluminum welding rods, set up your equipment and make some welds.
There is no substitute for experience and the best way to gain that experience is to burn some metal.
Follow the tips provided in this article. Follow the guidelines and instructions from the websites provided and, with practice, you will see your skills improve and your aluminum welds start to look like those you see produced in commercial shops.
You will have mistakes. You will make bad welds and good welds.
The object is to learn from your mistakes. The one thing you can be sure of is that your mistakes won’t be because of the aluminum welding rod.
By and large, the quality of the aluminum welding rods you will find at your local supplier will meet your needs and, eventually, your expectations.