Step-By-Step: How to Prevent Bubbles in Your Welds

Metal bubbles or porosity is something not liked by any welder. These bubbles cause instability in the welded metal and can be a serious defect. Honestly, all kinds of weld can have bubbles and there is a tolerable level of bubbles. But when the acceptable level is crossed, that’s where it starts to become a headache.

It is not possible to completely get rid of bubbles or porosities. But, if you take some steps during welding, you can surely reduce the risks of bubbles appearing in your welds. Bubbles are nothing but the trapped gas inside the weld. So, if you do something that does not let the gas be produced, you can prevent it at ease.

So now that you know that you can prevent bubbles or porosity in your welds, it’s time to know the process. In this article, I will talk about how to prevent bubbles in your welds and what causes them in the first place. So, if you are learning to weld, I highly advise that you read the whole article till the end. 

Causes of Air Bubbles in Your Welds

Air bubbles are annoying in metal builds, and there could be a lot of reasons behind air bubbles in your weld. In this section, I will talk about the causes of air bubbles in your welds. Then I will let you know about the prevention methods.

  • Presence of Air

Air can cause disturbance while the gas is being delivered to the welding process. If you have a fan in your welding room, the airflow can damage the shield of gas. 

Also, open doors can cause air to get inside your room. Air Flows faster than 4 miles per hour can seriously affect the welding quality of SMAW and FCAW.

  • Presence of Moisture

If the surface of the metal is moisturized, it can cause porosity. No matter its morning dew or simple water, it can be the cause of metal bubbles.

When the temperature of the water is less than 50° F, it can cause trouble. However, preheating can easily fix this issue and preheating is necessary for welding. 

  • Low Temperature

As I said before, preheating fixes a lot of issues and that’s true. Low temperature and rapid cooling can create bubbles in the final output. 

Do not rush and use high temperatures for welding. If the metal is not molded, the weld will not be good, and you will face higher chances of porosity.

  • Metal impurity

If the purity of the metal you are working with is not good, it may produce metal bubbles a lot. For welding, always try to use pure metal as it has fewer chances of porosity.

  • Lubricant

The mold of metal should not have too much lubricant. A higher amount of lubricant will separate the metal earlier than expected, and the cooling will not be efficient. As a result, you will see bubbles in the final build.

  • Stuff in the metal surface

The metal you need to weld should be polished before working. There should be no paint, oil, grease, sweat, or glue on the metal surface while you weld. 

When you use high temperature that stuff releases gas on the metal which eventually leads to air bubbles.

  • Oxidation

When the metal is welded with rust, you will see that some decomposition gas is being formed, which leads to oxidation. 

Oxidized metal is not pure metal, and you can expect to see bubbles from it. You need to take the necessary steps to avoid oxidation.

  • Galvanization with zinc

If you are plating the metal with zinc, it can cause porosity. Confused? Let me explain. The melting point of Zinc is 420° F. For welding, you surely reach more than 2000°. That much temperature turns zinc into gas. You know that zinc dust becomes a byproduct of welding.

So when zinc releases both gas and dust, it gets trapped inside the metal and causes the production of bubbles. Overcoming this is not easy as it requires a lot of practice. But eventually, you will learn to overcome the presence of zinc inside metal welds.

  • High gas flow

If the gas flow is too high for the weld, it can create turbulence. As a result, outside air will get inside the weld zone. 

You already know that air could cause those bubbles to pop up. Also, this is a waste of gas and money.

  • Inappropriate use of anti-spatter compounds

Inexperienced users often use sprays or gels incorrectly. If those anti-spatter compounds are not applied properly, they can convert to a gas when you use high temperatures. 

Ask an expert to apply the anti-spatter compounds so that it does not turn into a headache for you.

  • Inadequate electrode de-oxidant

When you cool the metal down for solidification, excessive oxygen might come out from your metal object. 

This happens because oxygen tries to react with other gases in the air. If it can get out, it can create carbon monoxide. But as it is trapped inside the metal, it causes air bubbles to form.

  • Flux issues

Flux absorbs moisture, and you need to use dry flux in order to make it effective. But if you use low-quality fluxes with low activity, it can produce air bubbles. Always use high activity flux for your job.

  • High arc length

If the length of your welding arc is too high, it can reduce the magnitude of the shielding. As a result, the air gets trapped inside the metal, and you know what happens if air gets inside your weld pool.

  • Electrode problem

Your electrode should have nothing but tungsten on it. If there is something else, the other metal might drip the electrode off. The electrode in the bead can cause air bubbles to form.

  • Faulty TIG torch angle

If your torch is not held at 90°, welding can get messed up. You need the shield gas to cover most of the areas. 

If your torch is held too flat, the weld will get oxidized because of the lack of shield gas. And I don’t have to tell you again how oxidized metal can create air bubbles.

Our recommended electrodes Hobart 770473 6013 Stick.
They burn clean and great for beginners.

Preventing Air Bubbles in Your Welds: Step-By-Step

From the previous section, you know the causes of air bubbles in your welds. In this section, I will talk about the prevention steps. I know this is what you came for, so try to be attentive here.

Step 1: Cleaning the materials

Before starting to weld the metal parts, clean them. There should be no oil, grease, moisture, or rust on the surface of your metal object. Because if you do not clean those stuff before welding, they can mix with the weld puddle while you raise the temperature up. 

Now when you cool the metal down, that stuff gets trapped inside the metal and causes the bubbles to be produced. If your parent material is coated using paint, zinc, or stuff like that, it can cause a chemical reaction and produce gas. You know what the gas can create, right?

T-joints can have more gas than butt-joints, even though you are welding both of the sides. Cleaning the outside layer of oxide is mandatory as your first step to the prevention of air bubbles. The pipes and tubes should also be cleaned and degreased before welding. 

A citrus degreaser can be used for cleaning dirt and grease. Grease can be a serious pain in the neck, so make sure there are no traces of grease in the metal. Also, do not forget to clean that degreaser too. If you have a really thick layer of grease, you can use a wire brush, make it loose and then start degreasing the metal.

While you are welding a part of some engine, remember that those parts can have oil in them. The trick of cleaning is to use a torch to heat the metal. The oil will sweat out, and then you can wipe it. Heat it again and check if your torch brings grease or not. If it does, clean it again and keep repeating until the metal is fully cleaned.

Step 2: Monitor the gas flow

You need to check the gas flow from the shield constantly. You know that the gas inside the metal creates bubbles, so the goal is to control it. If the gas is too powerful it can disturb the air which will help the contaminants to mix with the weld puddle.

The flow rate of the gas will vary, and it’s normal. But it’s your responsibility to control the rate, as it can change the quality of your weld. Not enough gas can create holes for air bubbles, and too much gas can cause issues in the weld pool. Before starting to weld, check if there is enough gas in the container. 

Also, control the gas flow so that too much gas cannot get inside. You can use a gas lens for reducing the high gas flow. If you are still unsure, I suggest you contact the supplier of the gas.

Step 3: Check your welding components

Maintenance of your welding components is important. No matter if you are having issues with metal bubbles or not, you must check the welding components each time you start welding. 

Check if the hoses are contaminated or not. If they are, you need to perform a cleaning operation first. Check the welding gun for worn-out copper wire as they are responsible for metal bubbles too. All of the welding components should be good enough to work with.

The gun liner should be clean and properly sized. Before each welding operation, you should check the contact tip and change it if necessary. Using the perfect size for contact tips is also important. It can get clogged sometimes so at least make sure that they are in perfect condition.

Step 4: Maintain workspace condition

The place where you are welding must have a calm condition with no sudden airflow. I know it can be a challenge to keep working with 3000 degrees of Fahrenheit with no airflow. But welding is a challenging job, and you must accept it. And when you are working so much, you don’t want it to go in vain.

Strong airflows can downgrade your welding quality and cause porosity. It affects the gas shield and does not allow the welding gas to penetrate correctly. Also, check the voltage/arc length while you are welding. If the welding gun is not closer to the weld site, the gas shield will become weaker.

If the gas shield cannot protect the weld puddle, air and gas will get into the puddle and that is harmful to the metal. You will see bubbles popping up because of that air and gas and that’s not something you were expecting to see. Airflow is a serious issue, and you should take good care of it.

Step 5: Grounding is important

Using an earth clamp for earth connection is important. Loose connections can be responsible for metal bubbles, and you should ground yourself before starting to work. 

Do not use a cheap earth connection, they won’t give you maximum protection from electrical issues. 

Step 6: Clean aluminum oxide

At this point, you might ask why did I write about the cleaning of aluminum oxide now while I have already mentioned cleaning at the first step? Well, cleaning aluminum oxide is not an ordinary case.

Aluminum creates a thin layer of oxide that is not good for TIG welding. You need to clean that layer just before starting to weld. Yes, you cannot clean it a few days before welding as the oxide layer is created fast. 

A stainless steel brush will be a perfect choice for scrubbing. Do not use the brush you use for cleaning other materials. Use a new brush or use something that you use for aluminum only. A brush that has been used before can have contaminants in it.

Some welders prefer using chemical agents. You will surely find a chemical agent that is designed for removing aluminum oxide at a welding supply house. Using AC instead of DC could help you remove the oxide layer. 

Step 7: Clean rod contamination

You clean metal before welding, right? But welding rods can also contain contamination, and they get dirty. 

So, you must clean your welding rod the way you clean metal. Wipe the rod down using acetone every single time you start welding. The rod might not look dirty, but you should clean it properly.

Step 8: Reduce pressure

The air inside the sealed pipe can heat up during welding, and the pressure from the back of the weld can get increased. In order to fix this, the inside of the pipe needs to be preheated. The air will expand, so the late pressure won’t happen anymore. If you are not able to preheat the pipe, you can get a drill machine to drill a tiny hole in the pipe.

The hole should be in the place where your weld finishes. The air will escape from the pipe using that hole, so the pressure will be equalized, and the air will not get trapped inside. After cooling the bead down, fill the hole but do not heat the pipe too much. You do not want to drill the hole again and again, do you?

Step 9: Start welding, slowly

Do not rush while starting to weld. Start slow, but keep welding steadily. That will make sure that the weld is done perfectly. Rushing can make the metal produce metal bubbles faster, so do not insert the welding tip too quickly. Control the wire feeding system by yourself.

If you do not feed the reel steadily, there will be no reel tension and you will see some extra wires getting released. Even though your gun trigger is released, the wire will mess things up in the weld puddle and get tangled. So being slow and steady is the key.

Step 10: Check electrode

If you notice that the electrode has touched the workpiece, stop your welding operation. At this point, you need to grind the electrode again and remove the electrode contamination. You might want to have some electrodes prepared so that you can just swap between them.

Grinding requires time, so having multiple electrodes is a plus point. Try to use clean electrodes for your welding operation.


Popping air bubbles is a permanent issue for the welders, and it cannot be fully prevented. But people must try to reduce it as much as possible. In this article, you read about the reasons behind porosity and learned how to prevent bubbles in your welds

Although I admit that you cannot fully prevent air bubbles from popping every single time, at least now you can take some prevention steps. Give your best at welding and I hope you will face fewer air bubbles in your welded metal from now. Good luck and I will catch you on another article.

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