Ar/Co2 for MIG Aluminum

[Alex]

If the addition of a small percentage of Co2 to Argon results in better penetration on steel, why wouldn't the same be true of aluminum? What would happen to the weld or HAZ if I used a 90/10 mix to mig al?

Alex

[sparx]

If the addition of a small percentage of Co2 to Argon results in better penetration on steel, why wouldn't the same be true of aluminum? What would happen to the weld or HAZ if I used a 90/10 mix to mig al?

Alex

(taken from the welding aluminum theory and practice book)
The only shielding gases to use for mig welding aluminum are argon, helium, or a mixture of the two. Other gases such as oxygen, nitrogen, carbon dioxide, or hydrogen, even in trace amounts, in the shielding gas will cause dirty and porous welds.

regards
Sparx

[ASKANDY]

The only way you would add any of those other gasses would be pulse mig but for standartd mig aluminum, NO Co2!

A-

[hankj]

When exposed only to the amounts of Oxygen and Carbon Dioxide that exist in the atmosphere, aluminum nearly instantly forms a coating on it's surface called aluminum oxide. The oxide coating is actually a protective coating; it keeps aluminum from corroding. Think of the coating on a mirror: the shiny, reflective "front" is aluminum; the dark grey coating on the back is aluminum oxide, formed only by exposure to air.

Unfortunately, that coating, when included in a weld, is what causes defects like embrittlement and porosity.

Considering that two of the elements found in air (O2 and CO2) cause oxides to form, it makes sense that we need to exclude them from the weld with some form of shielding to prevent the atmosphere from coming in contact with the weld metal.

You know the rest.

Hank