What Causes Pinholes in Welding?

Welding is a technical profession. It requires careful calculations and application of the welding arc at the right temperature and angle for the correct duration of time. Welders must also ensure that the environment is right. Strong wind and dust in the area can affect the quality of the weld and add impurities to it.

Welding pinholes are a common problem that can occur as a result of incorrect welding practices. In this article, we look at the reasons welding pinholes occur and what you can do to prevent them.

What Are Welding Pinholes?

Pinholes and welding porosity are cavities that can appear in a melded puddle after two pieces of metals are welded together. They are usually very tiny and can be as deep as the weld itself. Pinholes can make an otherwise perfect weld look less than perfect.

Possible Causes of Porosity and Pinholes

Porosity is usually caused by the contamination of gases trapped inside the meld. These gases are released during the welding process by the welding gun and absorbed by the molten metal.

When the puddle begins to cool, the atmospheric air also affects the joint and causes various shapes of holes to appear in the weld as the gases are released.

There are dozens of other reasons why pores appear in your welds. The most common reasons include the following.

  1. One of the most common reasons for welding pinholes is that your cylinder is almost out of gas. This causes an uneven gas flow to the arc and creates pinholes.
  2. If there is a lot of moisture in the air, it can cause water molecules to get trapped in the weld that creates pinholes. This happens particularly in cold weather, with temperatures below 50 degrees F.
  3. A strong wind, overhead fan, or breeze from the AC can also affect the delivery of gas to the arc and create imperfections for the welding process.
  4. If the welding gun’s nozzle is blocked or restricted for some reason, it can create tiny holes in your welding puddle due to uneven arc application.
  5. The welding gun nozzle must be held at the right distance from the joint and should be applied at the correct angle to spread the gas flow out. Check your welding blueprints to identify the correct angle and distance for the project.
  6. Different chemicals like grease, oil, paint, glue, etc. release a large volume of gases when they are heated to welding temperature. These gases can get trapped in the weld and create pinholes. Make sure that your project’s surface is free from chemical imperfections.
  7. Similar to chemicals, rust or zinc plating can also create unwanted gases that form porous holes in metal welds.
  8. The length of the gas hose also affects the arc quality. If the hose is more than 20 ft long, there is a good chance of it getting bent or kinked, which affects the arc and creates porous holes.
  9. Excessive use of anti-spatter gels, sprays, and compounds can also create unwanted gases during the welding process. If these gases are trapped in the weld, they can create pinholes.
  10. If the gas cylinders used for generating the arc are not handled carefully, the gas inside can get mixed with moisture. The contaminated gas may also create pinholes in the weld.
  11. If the gas hose is contaminated with moisture or other impurities, it can also cause porous holes in the weld.
  12. Cuts, burns, or dents in the hosepipe also affect the gas flow and could cause pinholes in the welded joint.
  13. Improper welds are also a common cause of porous joints. If the weld is even slightly open at the root, it can absorb air and create pores as the weld cools off.

How to Prevent Pinholes in Your Welds

The first step for preventing pinholes in your projects is to understand why these pinholes appear. Once you have identified reasons why it is happening, you can take positive actions to prevent them from showing up.

Maintain a Uniform Gas Supply

As identified above, the uneven gas flow is usually the biggest culprit for causing pinholes in your project. When the gas pressure is too low, too high, or becomes uneven during the welding process for any reason, it affects the arc and quality of the weld.

Make sure there are no obstructions in the gas flow from the tanks to the nozzle. Have your gas tanked filled with fuel and checked for impurities. Get your hose and nozzle cleared of any impurities. Ensure all the connections are secured tightly, and there are no leakages.

Protect Against Environmental Factors

A strong wind or air from your cooling fan can also affect the quality of the welding process and create pores in your metal joints. A strong gust of wind can disrupt the flow of shielding gas or cause oxidization that forms pores in the weld. So make sure that your welds are protected from strong wind.

Consider switching your projects indoor where you will have more control over the airflow. Turn the fan off if you need to. If you have to work outdoors, consider using cardboard boxes or metal sheets to create a barrier between your work area and a strong wind blowing in your direction.

Try to avoid working in very cold weather or conditions where there is a lot of moisture in the air. Keep your delivery hose, welding gun, and gas tanks clean from all impurities that can cause problems in welds.

Clear the Work Surface

Ideally, you should only work with clear, shiny metal plates and sheets. Make sure that your work surface is clear of all kinds of impurities, including rust, paint, oils, etc. Rust is particularly bad for welding because it is a type of oxidized metal. When it melts during the welding process, it accumulates air that can get trapped inside your welds and forms pinholes.

You can use paint thinners, acetone, or rust remover to clear away the impurities. You can also use oil and grease cleaners to liquefy and clean oils. Wipe the metal down with a clean rag after clearing away the chemicals.

If the metal surface is in a particularly bad condition, you can use a grinder to remove rust and corrosion. Use the grinder until you’ve knocked the rust off completely to reveal a gleaming metal surface.

Keep the Electrode Clean

The electrode on your welding gun can get contaminated from welding spatter. This affects the arc and causing an uneven flame, and pinholes may appear in your weld. Make sure to check the tungsten tip and keep it clean periodically.

For stick welding, make sure always to use a clean, dry rod. Keep the rod stored in a closed container and keep them away from chemicals, moisture, or other contaminants.

Apply the Arc Correctly

The way you apply the arc to the metal sheets can also cause porous holes to appear. For a start, the arc should not be too long or too far away from the weld puddle. When you hold it too far from the work-piece, it can cause problems with the bead. The ideal distance for most TIG and MIG welding is about 1/16th of an inch.

Make sure that you are not moving the gun too quickly. Maintain a steady rhythm of pushing and pulling the rod from the puddle to prevent holes from appearing in the weld.

When you are done with the weld, don’t cut off the arc abruptly because that can create pinholes. Use the hand control to taper the arc slowly and let the bead cool at a slow pace for a smooth finish.

About Pierre Young

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Hey, I'm Pierre Young a qualified AWS Certified Welder. I got into welding in 2009 as a side hustle. Ever since then, I've been doing all kinds of welds - both for business and pleasure. While immersing myself in this wonderful hobby, I've learned from hands-on experience what welding gear works and what doesn't. Welding Headquarters is the site where I share everything I've learned.

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