Category Archives: Causes of pinholes in MIG Welding

Causes of pinholes in MIG Welding

Today we are going to talk about the causes of pinholes in MIG welding, but first let us define the words to be used in this article. Pinholes aren’t really an uncommon occurrence in welding, in fact, they’re a little common. Welders encounter them from time to time. The smart welders know how to avoid the. Sometimes pinholes are being called as “porosity”.  Here is an image of pinholes, focus on where the light hits on the metal and you will see.


Of course, even if pinholes are common, they aren’t what welders would call as something good or expected in a finished product.  In fact, these are a welding defect. Often times, pinholes can be cause by too high welding temperatures. This is because there is a trapped gas inside and when it tries to push out of the surface, it forms into these little holes which aren’t really nice to look at. Don’t worry too much if you see pinholes in your weld, because they can be prevented, however, before we discuss that, let us first inform ourselves about what causes pinholes.


  • Moisture is a big bold NO in welding because it is one of the causes of pinholes. Just like in wounds, moisture is a frowned upon in welding because it can promote the growth of bacteria. How can you combat this? You can start by preheating the metal you are about to weld, or if you don’t want to preheat it, you could wipe it thoroughly and make sure that everything is already dry and ready to be used. Make sure that BOTH sides of the metal are clean, and also be sure to check out the wire you are going to use if it is free from rust and any dirt.  Don’t use a wire that has been contaminated with dirt, oil, grease, glue, and even paint. Aside from promoting the appearance of pinholes, the said substances when exposed to heat release poisonous fumes. You don’t want to inhale that.

    Cleanliness is important in welding.

  • You may also want to check the rate of your gas flow. Make sure that it isn’t too high or else you will be seeing pinholes in your weld.
  • If you are using a gas hose (which I believe you are), you should also take time to check that it isn’t kinked or squished. Make sure that the flow of gas is free and nothing is getting in the way.
  • Also you will have to pay attention to the distance between your weld nozzle to your weld puddle. Don’t align it too far away, but also don’t push it too close. You might need a little bit of practice with this, but I’m sure that you will get it right. You see, if the nozzle is a bit too far from the puddle, then the amount or the volume of the shielding gas will be diminished and you will see the effects. It won’t reach your puddle and the shielding gas may mix with the atmospheric air which can have a negative effect on your welding process.
  • In relation to the paragraph above, make sure that the air flow in the room is steady. A fan or an open window may mess up the shielding gas. As a welder, you need to be aware of the state or the condition of your room to make sure that nothing can mess up your  weld.


Those are the causes of pinholes so don’t forget them so you can avoid them and in responses, say goodbye to pinholes too.


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