What Causes Pinholes in Welding?

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Last Updated on August 15, 2021 by weldinghubs

Porosity and pinholes are common problems that can arise on a surface.

Porosity is the presence of small air pockets in the material, while a pinhole is an opening in the surface that allows for penetration into the interior.

Both porosity and pinholes may be caused by many factors including environmental conditions, manufacturing processes, or contact with materials such as water or solvents.

So, What Causes Pinholes in Welding? Welding pinholes happen when there is a problem with gas flow and moisture in the air. If your weld becomes humid or you run out of fuel, it may become porous due to water molecules that are trapped inside. The presence of pinholes in a welding joint makes the whole weld seem less than perfect.

There are several ways to fix these issues if they occur on your own work or someone else’s; it all depends on what type of porosity you’re dealing with and how severe it is.

This article will help identify possible causes of both porosity and pinholes so you can find out how to fix them.

Let’s get started!

What Are Welding Pinholes?

Sometimes welding can produce unsightly cavities in the metal, and these are commonly called pinholes. These tiny caverns may not seem like much of a problem at first glance, but they might be as deep as the weld itself which could make any otherwise perfect-looking joint less than desirable.

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What Are Possible Causes of Porosity and Pinholes?

There are many different factors that can lead to porosity and pinholes in welding. Some of these include the following:

  1. The cylinder is out of gas or not in position.
  2. The gas flow to the arc is uneven, causing a lack of pressure which creates pores or holes in your welds. Too much gas flow can disrupt the “weld puddle” and create pinholes or cracks.
  3. Moisture is a leading cause of problematic welding. Moisture can gather in the material being welded or as condensation from welding on thicker metal when it’s near or below 50 degrees Fahrenheit.
  4. Strong wind from an overhead fan or AC causes gas flow problems; if there’s limited airflow you may experience porous joints.
  5. Blocked welding guns produce tiny holes because they don’t disperse enough heat at one time. Fortunately, there are measures you can take to prevent them. Check on manufacturing specifications and chemical reactions that could potentially cause problems when the welder’s distance, angle, or speed changes those distances the gases it emits are release at different rates.
  6. Rust or zinc plating also creates unwanted gasses that form porous holes in metal welds, so make sure your project is free from chemical imperfections
  7. The length of the gas hose may affect arc quality; if it’s more than 20ft long there’s a good chance of kinks which could lead to porosity or pinholes due to improper flow of gas.
  8. One cause of pinholes in welding is the excessive use of anti-spatter compounds. To avoid this, be careful not to apply too much when working
  9. Pinholes may occur in welds when moisture from a gas cylinder mixes with the gas, creating contamination.
  10. Gas hoses are also prone to problems and may cause porosity if they’re contaminated. This can happen due to cuts in the hosepipe or burns from welding torches, which affect the flow of gas through it.
  11. Dust, dirt, and other airborne particles can also cause pores on metal surfaces. To fix these problems it’s best to use a high-quality mask so that you don’t inhale any of the dust when working with welds or piercing holes in the material
  12. Equipment such as gas hoses is prone to kinks which may lead to porous joints due to improper flow of gas through them. Be careful not to create too much pressure by overworking your equipment; make sure airflow is always present for quality welding jobs.
  13. The type of flux used during welding may be another reason why porosity forms on the surface because certain types trap gases inside while others allow air escape without trapping gases at all. It’s important to know your flux before using it because some may create pinholes in welds if not used correctly.
  14. Air or drafts disturb the protection of shielding gas during welding. This can happen due to an overhead or floor fans as far away as 25 feet away from the welding area, open doors, and air being discharged from machinery.
  15. This happens when the electrodes are exposed to moisture which is then absorbed by them. To avoid this situation, it’s recommended that they be kept in dryers or ovens where such conditions are more controlled. SAW flux in particular is like a sponge: once the package has been opened, it should be stored according to the manufacturer’s instructions.
  16. Cleaning of welds with a wire brush or grinding wheels leaves abrasive particles in the surface which will act like sandpaper on a rust or mill scale – this can lead to cold lapping at the joint interface after welding has been completed.
  17. The gas used to weld metals could be the cause of contamination. The welding company should ask their supplier for a certification that their tanks are up-to-date on safety measures in order to protect themselves and all those who work with them from harmful gases like ammonia or acetylene, which can both lead to corroding metal surfaces when mixed with water vapor.
  18. A contaminated hose can cause air to enter into weld joints from places like GMAW right on an outside corner joint or unprotected liquid metal absorbing air easily. The GMAW gun-whip connects to the wire feeder. The GTAW torch cap screws into the torch and has a connection that allows air in, too! Damaged O-ring seals or cut hoses can cause this.
  19. Gas solenoids at wire feeders and GTAW machines can cause porosity in welding.
  20. Welders are all too familiar with the problem of porosity in weld beads. This is a result that not many people want to see, but sometimes it happens anyway because there’s no shielding gas or atmospheric air gets inside and does some damage.

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How to Prevent Pinholes in Your Welds?

When welding with an arc, it is important to keep a steady rhythm of feeding and directing the electrode from puddle to pool. When finished welding with an arc be sure not abruptly cut off your connection because this can create pinholes in welds.

In general, the weld is the most important part of any welding project. It’s what holds everything together, and it’s what makes your work durable. But a poorly done weld can cause holes in your finished product. Luckily there are ways to prevent pinholes from forming when you’re working with metal rods or gas-shielded wires that produce heat and sparks.

I’m going to tell you how I compensated for pinholes in my welds.

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Make Sure There Is Uniform Gas Flow:

One of the most common causes for weld defects is uneven gas flow through the nozzle during the welding process. When this happens it will affect quality and arc stability.

Check your pressure settings to make sure they’re where you need them to be – too low or high can cause issues with how the gas flows through the nozzle.

A common reason for an uneven flow of gas is a blockage in a hose or connection point, so be sure to check those areas before you start welding anything.

If your pressure settings are correct and there’s still an issue with how the arc looks, it may be because the metal surface isn’t clean – you’ll need to scrape or sand it first before welding.

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Protect your welds against environmental factors:

Our welds are not only susceptible to the environment and heat changes, but also to wind and air pressure. A strong wind can disrupt the shielding gas and lead to pinholes in your welds.

So make sure your welds are protected from strong winds by working indoors. Having more control over airflow will also is helpful in the long run, as you can easily adjust it to maintain a safe and comfortable work environment.

Turn off fans if necessary. If you must work outside and are concerned about the wind potentially harming your welds, consider using a barrier such as cardboard boxes or metal sheets to block

Generally, you should avoid working outside during cold periods or in conditions where moisture is prevalent. It’s important to ensure that your welding equipment is free from dirt and moisture as well.

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Ensure a clear work surface:

Clear work surfaces are especially important when welding because they prevent rust from accumulating and creating pinholes in a weld.

It’s also vital to ensure that the metal surface is clear of any impurities, including oil or grease so that you can smoothly complete your weld. You should be able to see through your plate without seeing anything obstructing it.

You can keep your workspace clean by using paint thinners and acetone to dissolve the impurities coating the welding wire. You should also use oil and grease cleaners if you encounter any of these substances on the metal surface during welding.

If a certain area has been contaminated with an excessive amount of oils, then use a grinder to remove the rust. When you’ve knocked all of the rust off your metal surface, make sure it is completely free from any kind of impurities before beginning welding again.

A clear work surface is vital to ensuring that your weld has a perfect finish and does not come out with any kind of impurities. Ensure you keep the metal as free from rust, grease or oil build-up as possible so that it’s ready for welding.

Electrodes should be kept clean in order to avoid pinhole welds:

Cleaning the electrode on your welding gun can prevent contamination and other issues that may arise. Pinhole welds are a result of an uneven flame, which attracts contaminants to the area where you’re welding or stick welding.

The tungsten tip should be checked periodically for debris as well because this is what causes the arc to become distorted (causing the pinhole weld).

Stick welding rods should be kept clean and dry, away from any contaminants that may cause a pinhole weld. For both stick welding and flux-cored wire arc welding (FCAW), make sure to always use a clean rod for your next tack or weld. You can also replace contaminated electrodes before they affect your welds.

Make sure you are applying the arc to the joint at a proper distance:

One of the most important steps to welding a pinhole-free weld is keeping your arc short and closes enough. In order for starters, the arc should be an inch at max – and better yet, only 1/16th of an inch in size if you would rather use TIGs or MIG.

Moreover, if you’re not holding the weld far enough away from where it’s being applied, you may experience pinholes in your weld. The recommended distance is about an inch to avoid this issue.

When you finish the weld, make sure not to cut it off abruptly. Otherwise, there may be pinholes that go all through your welding job and ruin its quality. Using the control hand to taper the arc of electricity and letting it cool slowly will work towards achieving a smoother finished product.

How an Inspector Finds Holes in Your Welding?

When welders create a seam, they may experience porosity if not properly inspected. Here are some methods inspectors may use to identify these holes:

  1. Visual Inspection
  2. Dye Penetration Inspection (DPI)
  3. Soap Solution Test

01. Visual inspection:

Welding experts use a variety of inspection techniques to detect defects, including visual inspections. Although these methods are straightforward and effective for simple welds, they may not be highly accurate when it comes to detecting defects in more complex areas or welds that do not adhere to strict standards.

02. Dye Penetration Inspection (DPI):

The Dye Penetration Test is commonly known as penetrating testing. The inspector applies a strong colored dye to the welded surface, waits for it to absorb into the metal if possible, and then wipes off any excess liquid before leaving sometime on its own so that once again only what has penetrated will be visible on top of or within the fabric.

Next, the inspector sprinkles a glittery powder called “developer” onto the surface. This process draws out any of the dye that has been absorbed into the weld and makes it visible to ultraviolet light, depending on what type of dye was used.

03. Soap Solution Test:

This test is similar to when you’re testing a hose for leaks by spraying soapy water; the gas that is leaking will cause the soap solution to bubble. The amount of bubbling an inspector finds in a weld depends on how big and deep they find porosity in it had been found.

Inspectors may inspect your weld by inserting a cotton swab into the pores of the weld and making sure it comes out clean. They might also submerge the weld in water for 10 minutes, then check to see if there is any leakage.

After locating pinholes you need to address them before continuing to weld. The following is a guide for repairing pinholes in welds.

How do you fill a welding pinhole?

It is good practice to fill welding pinholes with a primer or paint, but it can also be left as-is. For maximum protection against corrosion, any hole in the metal surface should have something applied inside of it and over the top. It is best if that thing has an inert quality like a sealant (ie: silicone) or something that is paintable (ie: epoxy).

The easiest way to fill a weld hole with an epoxy primer is as follows.

Step-01: Clean and prep the area thoroughly, including power washing if necessary.

Step-02: Apply two coats of filler or glazing putty over the complete surface, allowing it to set before sanding.

Step-03: Apply a coat of epoxy primer over the filler or glazing putty, and allow it to harden for 24 hours before sanding again.

Step-04: Finish with paint if desired.


Welding pinholes are a common problem in welding. Knowing the causes, prevention methods and inspection techniques will help you to avoid this problem altogether or fix it if it happens. If your welds have holes in them, don’t worry! We’ll give you tips for how to fill them up so they’re not an issue anymore. Pinhole-free welds await you now that we’ve given all of these helpful hints on how to prevent porosity and pinholes from happening again – good luck.

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