Defective weld job with lots of holes

Welding Porosity: Causes and Prevention Strategies

Whether it’s a part-time job, your career of twenty years, or just a hobby you’re getting into, there’s no denying that welding is difficult. Not only are there seemingly dozens of processes to learn and master, but there are tons of metals you need to learn how to navigate.

Plus, each metal and interaction between gasses can carry with it a new problem. This helpful guide breaks down the issue of welding porosity and discusses why this common welding defect occurs.

What Is Welding Porosity?

Welding porosity refers to a welding defect that occurs when oxidation and negative atmospheric particles get into a welding process. This occurs when the process is not effectively shielded from such effects. Certain metals have chemical changes as they heat up during welding.

A good example is aluminum – this molten metal attracts hydrogen atoms. These hydrogen atoms stick around even after the weld metal has cooled, forming tiny gas pockets in the hardened weld surface. These gas pockets are visible as a collection of tiny holes or pores.

As you might suspect, having a weld full of tiny holes doesn’t lead to the most structurally intact weld, so weld porosity is definitely something to be avoided. A weld full of holes is usually weaker, more brittle, and sometimes even more prone to corrosion. Now let’s get into ways that you can try to prevent porosity from occurring by using a proper welding technique.

Using Gas Shields

One method that certain welding processes, like tungsten inert gas or TIG welding, use is to release a steady stream of gas to surround the welding process. As the electrode heats up, turns molten, and is deposited onto the weld joint, it is surrounded by a cloud of gas such as argon. This gas effectively keeps any particles from the air from getting into the weld. 

Certain metals attract certain atoms when they heat up. While aluminum attracts hydrogen, another weld metal might attract nitrogen. This is why it’s crucial to know exactly how your metals behave when exposed to welding. You can’t just use the same gas shield for every metal. You’ll need to have specific knowledge of the make of your electrodes, the metals you’re joining, and more.

Ensuring Your Equipment Is Up to Par

It's a major achievement–and important to your welding process–to figure out what kind of gas you should be using to keep the atmosphere out of your welds.

However, somewhere down the line you might encounter an issue where you get porous welds despite blasting your welding process with argon, helium, or some other shielding gas. If this is the case, you should check to ensure your welding equipment is working properly.

If a seal is loose or something isn’t screwed on tight, then it could mean that air is leaking into your shielding gas stream. This would mean you were essentially blasting the weld with oxidation directly. The atmosphere is full of gasses, so you will probably be damaging at least some welds if this occurs. So, let’s look at specific welding equipment you can examine to make sure this doesn’t become a problem.

First, look out for O-rings that show signs of wear and tear. These form a tight seal in your gas-emitting nozzle, so if yours looks cracked, flimsy, or old, it’s probably time for a replacement.

The good news is that this is a pretty inexpensive repair, as long as you catch it before it causes damage to a welding job. You’ll also want to check for cracked MIG welding liners. Additionally, if any pieces seem loose when they were once tightly fitting together, this is something to note because it could be a sign that it’s time for a tune up.

Spongy metal from welding porosity

Make Sure You’re Welding Properly

Something else that can lead to welding porosity is improper technique. If you’re not welding correctly, then it could be the cause of a whole host of problems.

While we’re sure that this is probably the first thing that many of you considered, it’s very common to gradually pick up bad habits that you might not even notice you’re doing. These bad habits can culminate in new issues.

This is one reason why it’s never a bad idea to talk to more experienced welders, take classes, and continue exposing yourself to new knowledge all the time. Keep learning and improving your trade so that you always stay on top of your game.

A common welding error is excessive movements, which can impact your shielding gas and expose the weld puddle to the air. You’ll also want to check and double-check your welding angles to ensure your weld is enveloped in gasses for the entire time. Too extreme an angle can produce excessive slag, as well as a porosity defect.

Finally, watch your welding speed and ensure you’re not ending your weld bead too quickly. A TIG weld bead needs to be completed slowly, with the shielding gas being gradually turned down to avoid the formation of a crater.

Holes in welded metal surface

Better Understanding Welding Porosity

Welding is an art that no one wants to get wrong, as it’s always so obvious when something has gone awry. Not only can it be unsightly, but the wrong welding mistake can cause serious safety concerns as well. That’s why it’s important to make sure you’re aware of what can go wrong in various welding situations and know how to counter them to get the best results.

Mistakes are inevitable, whether welding is your job or your hobby, and we can all learn from our mistakes. But hopefully this guide will enable you to learn from our experience so you’re better able to deal with any welding porosity issues you encounter in your future metal-joining endeavors. Good luck!

Back to blog