Cleaning aluminum for welding is an important stage that cannot be avoided if you want to make strong weld joints. Unlike steel and certain other metals, aluminum requires special treatment, and dirty surfaces can ruin the weld before you even strike an arc.
In this article, we will take a closer look at how to clean aluminum for welding.
Are There Any Challenges When Welding Aluminum?
Yes, preparing aluminum for welding is important because this metal has a greater potential for problems, such as lack of penetration caused by high thermal conductivity, porosity caused by high solubility of hydrogen, and a lack of fusion caused by a tougher oxide layer.
Any hydrocarbons or moisture should be eliminated from the surfaces, and the oxide film thickness must be controlled to prevent hydrating.
Is It OK To Weld Dirty Aluminum?
Cleaning aluminum for welding is an absolute requirement because the metal will be coated with oil and grease after it arrives from the factory. When aluminum is welded, there are unique challenges to overcome, and welding with a dirty base and filler metals will degrade the weld quality.
Ways To Clean Aluminum Before Welding
The presence of dirt and impurities will degrade the weld quality in all metals. So, when you’re preparing aluminum for welding, there are two main stages to consider:
It’s important to degrease the aluminum to remove residual contaminants and moisture. Wiping the surface with a rag to remove oil or grease is inefficient, and you can even spread contaminants over a larger area.
Use an aluminum cleaner for welding; a liquid degreaser, such as an organic solvent or alkaline solution, can be very effective. Some examples include lacquer thinners, acetone, toluene, and methylethylketone. Don’t use liquid cleaners that contain alcohol.
2. Removing Oxidation Layers
When the grease is removed, it’s time to remove any oxides that are present. This process starts with manual removal from the surface with a wire brush and a strong alkaline chemical solution. Use a wire brush with softer bristles and the chemical solution as the oxide removal agent.
Equipment Needed To Clean Aluminum
To clean aluminum, you need the following equipment:
- A vinegar and oxide removal spray that usually comes in an aerosol spray format or bottle for easier application. If you prefer, you can use white vinegar poured into a clean spray bottle instead.
- Clean microfiber cloths are needed to wipe the aluminum surface after degreasing and completing the deoxidation process.
- A soft stainless steel wire brush is used to scrub away any remaining deposits of oxidation from the surface.
- Immersion in hot water will give you optimal cleaning conditions.
- Brown Kraft paper is useful for storage if you’re not planning to weld the aluminum immediately. Wrap the metal in the paper to prevent contamination and re-oxidation.
- Packing tape is ideal to hold the brown kraft paper in place during wrapping, but if it comes into direct contact with the aluminum, it will contaminate the surface.
What To Do And What Not To Do When Cleaning Aluminum
What to Do
- Clear the table and cover it with a clean cloth or towel.
- Set up for cleaning near a sink with access to hot water if you’re planning to use mild alkaline soap solutions to clean the aluminum.
- Clean the equipment in between the cleaning processes to minimize contamination.
- Always have an eyewash station nearby for emergencies.
What to Avoid
- Avoid the urge to use compressed air because it will transfer moisture to the surface of the aluminum.
- Don’t wipe the surface with shop rags even if they look clean because they have lint and other contaminants that can compromise the weld quality.
- If you trim aluminum during preparation, avoid using oxygen fuel gas because it produces moisture during the combustion process.
What Are The Disadvantages Of Welding Dirty Aluminum
There are four main disadvantages when you weld dirty aluminum surfaces:
- The Fusion is Compromised: The presence of contaminants can cause problems with infusion, and this weakens weld bonds.
- An Erratic Arc: The arc can splatter, which spreads the slag to distant edges resulting in a weld that’s unprofessional and hard to clean.
- Contaminants Increase Resistance: A dirty surface increases the need for heat, and this can spread the weld surface wider.
- The Creation of Soot: When aluminum is contaminated, you may notice a black flaw on the weld surface instead of a clean weld finish.
Advantages Of Aluminum Being Cleaned Before Welding
There are three main advantages when you’re cleaning and preparing aluminum for welding:
- No Porosity: A clean and strong weld should have no porosity, which is the metal quality after oxidation, and the hydrocarbons are welded into them. If the weld is porous, the tensile strength of the weld is compromised.
- Consistent Welds: When the weld is clean, you can maximize the aluminum used as a controlled variable that will ultimately affect the welding performance.
- Satisfactory Welding: When the aluminum is clean and free from contaminants, and the welding is unsatisfactory, it’s easy to rule out contamination as the root cause.
After Cleaning Aluminum, How Should You Store The Aluminum Before Welding It.
Clean aluminum should be stored vertically with a brown Kraft paper cover to prevent the formation of condensation between the layers of metal that can occur during temperature changes.
Cleaning Aluminum for Welding–FAQ’s
Why is it important to clean aluminum oxide from the surface of aluminum just before MIG welding?
The presence of oxides on the surface of MIG filler metals can cause problems, including an erratic arc, sooting issues, poor feeding, and added resistance. The thicker layers of oxide on aluminum base metal must be mechanically removed to avoid weld contamination. Read more about Welding Aluminum with a MIG welder
What should you not clean aluminum with?
Don’t scrub aluminum surfaces with abrasive pads or metal brushes because this soft metal is easily scratched and damaged.
What can I use to remove oxidation from aluminum?
The most common way to remove the aluminum oxide layer from aluminum is with a soft stainless steel wire brush. This brush should be dedicated for this purpose to prevent cross-contamination to the aluminum from other sources. To reach tight areas or for heavier aluminum pieces, you can use a carbide bur.
But, these are usually air powered, and the air tool exhaust has the potential to introduce condensation or oil into the weld joint. So, it’s important to keep the air tool exhaust well away from the surfaces to prevent contamination.
Cleaning Aluminum for Welding–In Conclusion:
As you can see, cleaning aluminum for welding is an important process to create clean and strong welds. The most simple options are degreasing and deoxidizing, followed by proper storage if the welding is not immediate. Before you begin cleaning, it’s a great idea to have all the equipment and materials you need to make the process easier and limit contamination problems.