Aluminum is expensive. And the biggest problem with welding Aluminum is because the metal is not clean enough.
MIG Welding or TIG welding Aluminum?
Then the right wire brush for Aluminum should be part of your tool box.
Here I take you through finding the right scratch brush to use on your Aluminum, when to use it and how to use it for the best clean.
Can You Wire Brush Aluminum?
Can you use a wire brush on Aluminum is one of the first question questions asked by those welders who are new to handling Aluminum.
Yes you can use a wire scratch brush. But because of Aluminum’s special properties you need to be careful what wire brush you use.
What are the Special Properties of Aluminum?
Aluminum is a relatively light and soft metal. It is much softer than mild carbon steel. Aluminum has a lower melting point than steel, which means when you weld it, it is easy to burn through and put holes in your Aluminum.
It is shiny and attractive to look at so is often used where its strength, lightness and resistance to rust is an advantage. And this often means the outside of buildings, on boats and for railings. These are just a few of the many places it is used.
Yet Aluminum is reactive with air. So reactive that within a short time a layer of Aluminum Oxide builds up coating the surface.
Water vapor, moisture, or just plain dirt will mark the surface turning it a dull grey.
Why is this important?
Because before you weld repair or weld new fresh from the factory Aluminum the Aluminum Oxide or dirt has to be removed first.
Why Do You Use a Wire Brush on Aluminum?
A wire brush is an important part of the process of cleaning Aluminum. It is not the only part of getting Aluminum clean enough to weld well. Though it is an key step in the process.
A wire brush, often called a wire scratch brush is used to take the final layer of Aluminum oxide off the sheet metal.
Aluminum oxide melts at a much higher temperature than the Aluminum below it. Whether you are MIG or TIG welding, this means that welding without removing the Aluminum oxide first leads to problems striking the arc. Along with an inconsistent melting of the Aluminum underneath.
Dirty Aluminum results in a poor weld with porosity (small holes within your weld), black specs and excessive soot.
What Type of Wire Brush is Used for Aluminum
A scratch brush with stainless steel bristles is the wire brush of choice on Aluminum.
This is because the brush is abrasive enough to scratch through the covering of the Aluminum oxide removing it. Yet retains its composition and doesn’t break off tiny specs of stainless steel onto and into the soft Aluminum below the oxide layer.
Wire Scratch Brushes Not to use On Aluminum
Never use a scratch brush made of carbon steel as:
- It won’t be as effective breaking through the oxide layer.
- Not only that you will be embedding flecks of steel into your Aluminum resulting in a disastrous weld.
- And those flecks of carbon will rust over time, leaving you with rust all over your beautiful Aluminum.
It is best not to use a brass scratch brush either because:
- A brass brush will struggle getting through the Aluminum Oxide layer.
- You don’t want to risk leaving minute flecks of brass on your Aluminum, to cause you huge problems when you weld.
- Not only that but Aluminum, brass and salt water is a combination to be avoided.
You could accidentally end up with that mix. For example.
Your Aluminum part, remember that part you used a brass scratch brush on, that is covered in minute specks of brass and is now outside.
Say, in a marine environment. Or during the winter when salting of the roads splashes salt water up onto your Aluminum part.
The brass and the Aluminum act like different ends of a battery in contact with salt water. Causing your Aluminum to very slowly dissolve …
When to Use your Stainless Steel Wire Scratch Brush
Taking your stainless steel bristle brush to your Aluminum is not the first step in the process of cleaning your Aluminum.
Dirty Aluminum is more obvious. Metal exposed to the elements, out in the rain, and sunshine will be grey and have a thick layer of Aluminum oxide on it.
Along with more obvious watermarks, dirt and grime.
Even Aluminum fresh and shiny straight from the supplier or manufacturer needs cleaning before you even think of taking your welder to it.
It may not be obvious to you but even fresh Aluminum will have a layer of oil or grease on it. A layer of oil helps to cut down on the Aluminum Oxide build up on the surface but doesn’t prevent it all together.
Plus handling of your Aluminum transfers the natural oils from your hands.
Clean the Aluminum By:
1. Using Acetone and a clean lint free cloth to wipe off oil and grease on the surface. Not your wire brush for Aluminum. Using a scratch brush at this stage will only smear the oil and grease around with the brush’s bristles. Potentially burying it deeper into the surface and trapping it.
Acetone is perfectly safe for cleaning oil and grease off Aluminum. In fact it is one of the best solvents to use. Acetone does no harm to the Aluminum at all, and best of all it evaporates quickly. Meaning there is no residue to cause problems with your weld.
If you don’t have access to 100% Acetone, then a strong soap solution can be used. But you will then need to wash it off your Aluminum and dry thoroughly.
2. Use a grinder and a flap disc designed for use on Aluminum to remove the dirt, watermarks and Aluminum oxide. It is important to use a flap disc for Aluminum on Aluminum. As other discs may well heat the surface of the Aluminum polishing the Aluminum oxide but not removing it at all.
3. As a final pass across your welding surface use your scratch brush for Aluminum to get rid of any residual Aluminum oxide. Wipe with a fresh lint free cloth (not the same one you used earlier to remove the grease), to wipe away the last of the Aluminum oxide.
4. Now you are ready to weld on clean, well prepared Aluminum.
Bear in mind that Aluminum is highly reactive with air. And left for hours in even the best workshop conditions, will result in a layer of Aluminum Oxide build up.
Not to mention shop dust settling on the surface.
If you are not TIG or MIG welding straight away but have gone through this process, you may well get away with using just your wire brush to remove the small build up of a few hours of Aluminum oxide.
When To Use A Wire Brush for Aluminum Welding
- A wire brush is used just before you weld to remove the last of the Aluminum Oxide off the surface of the Aluminum.
- Between weld passes when filling a beveled weld joint. Any formations of Aluminum Oxide on the surface as well as any contaminants need to be scratched off by the wire brush before the next weld pass.
- After you have welded. To remove any soot, black specs and contamination that your Aluminum filler metal has driven to the surface.
How to Wire Brush Aluminum
To effectively use your wire scratch brush on Aluminum, it is best to brush in one direction then the other. What do I mean by this?
1. Don’t brush too hard. You want to remove the Aluminum oxide but not embed any surface contaminants into your soft Aluminum.
2. Brush up and down. From top to bottom, moving across the surface you want clean.
3. Then brush left to right.
4. Finally take a clean lint free cloth and wipe. Then you are ready to weld. If the weld has to absolutely spotless then you can follow your scratch brush clean with Scotchbrite.
Wire Brush Tips For Aluminum
- Only use a stainless steel wire scratch brush on Aluminum
- Keep the stainless steel scratch brush you use on Aluminum only for Aluminum. Clearly mark your brush with a sharpie so there is no doubt. Aluminum is so easily contaminated by other metals, you’ll only regret swapping your scratch brush back forth as soon as you have a poor, porous TIG weld.
- Don’t press too hard on your stainless steel bristles.
- Choose wooden handles that are heat treated, so that they won’t be affected by mold and last you a long time.
- Chose a wire brush with quality bristles. You want the bristles to stay on the brush not all over your Aluminum.
- You may need several widths of scratch brushes. For example a narrow brush to get into the small corner space of a fillet weld.
- Choose a brush length according to the size of your hands. A brush that fits your hands is much easier for you to use.
Finding The Best Wire Brush for Aluminum
Now you know what type of brush you need and when to use it, you need now to source a good quality brush.
I’ve found and would like to recommend my top three best wire scratch brushes for you to use on your Aluminum project.
1. Top Stainless Steel Scratch Brush for Aluminum
The Forney has a wooden handle and stainless steel wire bristles in 4 x 16 rows.
It is 10 and a 1/4 inch long.
Reasons to Buy
Forney is a great name in the welding industry and this brush lives up to the Forney build quality. For the price its probably a much better quality scratch brush than you’d expect.
2. Runner up
A wooden handled scratch brush with a 6 inch bristle area. It 13 and 11/16 inches long. Good for those of us with larger hands.
Reasons to Buy
This heavy duty stainless steel scratch brush is ideal for Aluminum. The handle is made of hard wood and is kiln dried to keep the handle looking better longer
The Osborn stands up to use well and continues to look like it is new even after a lot of use.
3. Also Great
7 and 3/4 inches long and 0.45 inches wide.
Reasons to Buy
Lincoln Electric is another great name in the welding industry known for producing great products
The wooden handle is heat treated to last a long time and resist mold. This scratch brush has a narrow profile, ideal for those tight spaces. Its stainless steel bristles are designed to stay put and last.
I hope you found my article “Find the Right Wire Brush for Aluminum (and How to Use It)” useful. Feel free to explore my other articles on the site about working with and welding Aluminum.