Q: I am having considerable problems with unacceptable amounts of porosity in my welds. I am using 75/25 argon helium mix, 5356, 3/64 in. wire on 5086 base metal. I have tried many things to correct this issue and have had no success, can you help?

A: To solve a porosity problem with welding aluminum, the solution is seldom just one thing but a combination of several seemingly small details that are overlooked. The porosity you are getting either is coming from inadequate gas shielding or from a source of hydrogen that you have not found.

In the case of inadequate gas coverage, you need to address both gas supply and environmental issues. The following are some things to check.

1. Verify your gas flow. Gas flow should be in the 40 scfh range. Verify that there are no leaks in your shielding gas system. Verify that the gun liner and gun connection to the wire feeder are installed correctly, and that O-rings are installed correctly and in good condition.
2. Make sure you are welding in an area where there is NO air movement...and I mean NO air movement. You are using a gas that has elements that are lighter than air, and they can be blown away easily.
3. Proper electrical stickout and gun angle also are critical to achieving a good weld with no porosity. Use a distance of about 5/8 in. from the end of the contact tip to the top of the arc. A push angle also is required...do NOT use a drag angle.

Hydrogen is the root cause of most porosity when welding aluminum. When you focus at solving your problem you will have to be very careful to address all of the sources of hydrogen.

You should consider the following suggestions:

• Remove any anodizing with a sanding disk. Use a disk that is appropriate for aluminum and that has been used only on aluminum.
• If you are machining a groove, you have to do this dry which means no cutting fluid…and, further, DO NOT use compressed air to blow off the surface to remove chips. Oil and moisture in compressed air is a real problem.
• Use a good degreaser that is made for aluminum and welding. Again, do not blow off with compressed air.
• Immediately prior to welding, use a good, fresh stainless steel wire brush to remove any aluminum oxide that has formed on the surface. If you use a wire wheel, be careful not to use excessive force because this will imbed the oxide along with other hydrocarbons into the surface.
• When welding you should make sure you are using wire that is of good quality and has been properly stored to minimize hydrogen. Make sure you have a good clean gun liner that is only use for welding aluminum. If you are using other alloys through the same liner, the aluminum could become contaminated with hydrocarbons. Clean the drive rolls with a good quality degreaser to remove any potential hydrocarbon containing material.
• Lastly you have to use an appropriate welding procedure for the application. There are many sources available on the Internet for welding procedures for aluminum such as Lincoln Electric’s Aluminum Welding Guide, which is available as a free download.