How to Prevent Porosity When You Weld Aluminium

Some DIY welders discover that the aluminium product that they have welded is porous after the fabrication process. This porosity can cause the material to leak in case it is used to transport a fluid or gas. This article discusses how you can prevent porosity from afflicting the aluminium that you have welded in your home-based workshop. 

Clean the Aluminium

Hot aluminium readily absorbs hydrogen gas. This trapped gas forms pores once the sheet metal cools down. The hydrogen may be absorbed into the aluminium if you do not clean the aluminium thoroughly before you start welding it. Surface contaminants such as water and grease release hydrogen once they are heated. It is therefore very important for you to make sure that the aluminium sheet is clean before you start welding it. Use a lint-free dry rag to remove any surface moisture. Use a wire brush to scrub the surface of the weld area so that you can deoxidise the surface that you are going to weld. These two measures will remove the most common sources of hydrogen that result in porosity.

Adjust the Work Distance

The distance between the weld nozzle and your aluminium sheet can have an effect on whether porosity occurs or not. The larger this distance is, the higher the chance that the welding tool nozzle will suck air from the atmosphere. That air will be heated and broken to release hydrogen gas. You can prevent this from happening by minimising the work distance so that there is no chance of contaminants getting into the weld gas.

Change the Flow Rate of the Gas

Many welding guns allow the user to adjust the gas flow rate based on the properties of the weld material. A slow gas flow rate may allow contaminants to get into the gas as it flows to the weld surface. It is better to increase the weld gas flow-rate if you are welding aluminium so that you reduce the time that the gas takes before it reaches the weld zone on the material. However, you should make sure that you do not exceed the flow rate indicated in the user manual of your welding equipment so that you don't exceed the safe flow-rate limits.

Once you address the issues above, porosity will no longer be observed in any aluminium item that you weld. If the problem persists, consult a sheet metal fabricator for advice on how you can keep porosity at bay when you perform DIY aluminium welding projects.