How to Clean Aluminum After Welding

Several DIY welding enthusiasts together with professionals working with aluminum welding know how it gets tinted during the welding process. The tinting diminishes the aluminum’s aesthetic look of the finished project and makes it have an amateurish look. This is the reason why most welders are always researching how best to clean aluminum after welding.

In this article, we will be explaining how to clean aluminum after welding, different types of cleaning, and the essential equipment you need to help ensure efficient cleaning.

Dos and Don’ts of Cleaning Aluminum Welds

Cleaning aluminum welds is a process that requires special care and attention. Incorrect cleaning of the weld seam can result in a defective aluminum product. When cleaning aluminum weld seams, a few rules must be observed. Every step in the cleaning process must be done carefully. Here is a list of dos and don’ts for cleaning aluminum welds.

  • Cutting methods that leave a ground or smeared surface should not be used under any circumstances. For example, a surface sawn with a tape can cause smudging. A high-speed circular saw should be used to cut aluminum. Similarly, grinders should be kept away to get a clean aluminum weld. Coarse grinders can be used with a wheel grinder if necessary. The point of cutting is to be sharp and fast without smearing or smudging. Before welding the aluminum, the stains on the surface must be cleaned to avoid a lack of fusion.
  • The use of oxy-fuel gas cutting, carbon arc cutting, gauging processes or oxy-fuel flames for preheating should be avoided. These cause damage to the heat affected areas and facilitate the growth and hydration of the oxide film present on the surface. Plasma cutting and gouging are more conducive to cleaner aluminum welds. This is because these processes usually don’t allow hydrogen and moisture to mix with the oxide layer.
  • Lubricants should never be used when welding aluminum. Petroleum-based lubricants consist of hydrocarbons that dissolve during the welding process and thus allow hydrogen to be added to the joint. This causes porosity and cracking, two processes that bring the quality of the finished aluminum product below the norm.
  • Oil and grease come attached to the aluminum from the factory. The joint should be cleaned before assembly. This can be done using degreasing solvents. Once that is applied, a cheesecloth or paper towel can be used to clean and dry the welding point. Cheesecloth and paper towels provide effective cleaning because they are porous, and hence absorb more oils and moisture. The opposite side of the joint has to be wiped clean as well to prevent impurities from being pulled through the aluminum and into the weld puddle.
  • Never use workshop rags to clean the welded joint. Oil and dirt can be transferred from these rags to the welding surface.
  • A wire brush can only be used to clean the joint after the solvent cleaning is complete, otherwise hydrocarbons and other contaminants will be implanted on the surface of the weld joint.
  • Never blow off the joint with compressed air. Moisture and oil contaminants are often present in compressed air.

Types of Aluminum Weld Cleaning

There are three different types you can always use to help clean aluminum after welding. Below is a review of the cleaning methods:

1. Mechanical Weld Cleaning

This is a common and low-cost aluminum cleaning method. It comprises grinding machines and abrasives to ensure the top layer of the aluminum surface where rust and other slag particles form are properly cleaned.

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However, this process is known to consume lots of time and one will rarely achieve a 100% cleaning result with the right aesthetic value.  It is a perfect method to use in areas that are easy to reach.

2. Chemical Weld Cleaning

This is the most popular method when it comes to aluminum cleaning after welding. It comprises the use of a chemical pickling paste which is normally applied to the areas affected using a spray or brush and left on the surface for some time for it to interact with the aluminum metal. After a few hours, it is removed and the surface is neutralized using a neutralizing agent.

Chemical weld cleaning is considered to be a very effective cleaning process after the fabrication process although there are welders who shy away from using it due to a number of reasons.

Chemical pickling paste is known to contain different toxic acids such as sulfur, nitric and hydrofluoric acids. These chemicals are known to be quite dangerous to the human body and are capable of causing long-term and serious damage to the human’s internal organs and skin when inhaled or consumed.

It is advisable that only a certified operator handles the chemicals pickling paste. The operator will have to ensure their full body is well covered to ensure their body is completely covered hence no chance of the acid getting into their body. This is the reason why pickling paste is normally used for commercial purposes or in automated sites only.

3. Electrochemical Weld Cleaning

Electrochemical also referred to as electropolishing is the most effective when it comes to cleaning aluminum after welding. It is safer and faster making most welders prefer using it when compared to the other methods. There are no major health risks associated with using this method.

Apart from cleaning aluminum after welding, this method is also effective in rust removal, cross-contamination, and other types of impurities from aluminum surfaces.

Essential Equipment to Aid in Cleaning Aluminum after Welding

1. Clean and Fresh Microfiber Rags

It is advisable that you get new rags to help in wiping wet aluminum surfaces after removing grease. Ensure the rags are clean and dry before you start wiping aluminum surfaces after you are through the deoxidation process.

2. Oxide Removal Spray and Vinegar

Oxide removal sprays are usually in the form of bottled substances or aerosol sprays. White vinegar is also an important oxide removal agent, especially when used on aluminum surfaces.

3. Wire Brush

It is highly recommended that you use a wire brush having soft bristles to scrub away any oxidation presence from the surface of the aluminum.

4. Hot Water

To ensure the optimal effect, ensure you immerse the aluminum in hot water before you embark on the cleaning process.

5. Brown Kraft Paper

This Brown Kraft Paper is very important when it comes to storing aluminum after cleaning. In case you do not have any plans to do another welding soon and do not want to clean again, ensure you wrap the aluminum using the Brown Kraft Paper to help prevent re-oxidation and contamination.

6. Packing Tape

Packing tape is not a cleaning equipment piece but is very important when it comes to aluminum cleaning. When you are done wrapping the aluminum with brown kraft paper, you will need the packing tape to help hold it in place.

You need to ensure the packing tape does not come into direct contact with the aluminum to avoid any form of contamination.

Cleaning Procedure

Dirt and any other form of impurity will always affect the weld quality of aluminum. Whenever you are done with welding aluminum it is advisable that you perform the two steps below.

Degrease Aluminum to get rid of Moisture of Residual Contaminants

Impurities like grease and oil will always affect the weld quality. Although it is possible to use a rag to help in wiping off the oil or grease, it is not a reliable and efficient method as you risk spreading the grease or oil to other parts of the aluminum.

To help in ensuring you have removed all the impurities, it is advisable that you use liquid degreasers such as organic solvents and alkaline solutions. Some perfect examples include acetone, toluene, lacquer thinner, and methyl ethyl ketone.

Do away With All Oxidation Layers

After you are done with removing grease, you can now get rid of the aluminum of present oxides. This is a process that involves manual material removal from the surface of the aluminum. You can always use a chemical solution or wire brush.

Whenever you are using a wire brush, go for one with soft bristles instead of one with hard bristles. Ensure you choose a strong alkaline chemical solution as an oxide removal agent.

Conclusion

Cleaning aluminum after welding is very important as it helps in ensuring the weld is sturdy. Degreasing and deoxidizing are excellent cleaning options you can always rely on. However, before you embark on the cleaning process, it is advisable that you ensure you have all the equipment you intend to use in place.

We hope you are now aware of how to clean aluminum after welding. In case of any questions or clarifications, do not hesitate to get in touch with us.