MIG Welding vehicle body with surface rust.

[Kawasakifreak]

Hi,
I've read your advice about grinding-off rust before MIG welding mild steel.
I understood that CO2 combines well with rust so why the need for clean metal before welding ?
Also, can anyone explain the advantage of 100% CO2 gas shielding versus 86/14% Argon/CO2 when welding vehicle panels pls ?
Kawasakifreak

 

[R Kraft]

The fluxing agents in the wire cannot cope with large amounts of contaminants, so you need clean metal.
Pure CO2 is not what I would recommend for thin panels, too hot ,use argon mix if you can.
Co2 works well on thicker metal.
Robert

 

[HOUNDMAGNET]

A weld will only fuse properly if the metal is clean of all surface contaminants.

The best gas for thin metals (upto 8mm) is a co2/argon mix...the most popular are coogar from air products (thats what i use) and its boc equiv argoshield lite.
Coogar and it argolite contain 93% argon / 5% c02 / 2% oxygen

Argon gives a true MIG process as it is inert,wheras co2 Is a MAG process as its an active gas.
The more co2 the more the spatter as well.

 

[Kawasakifreak]

Thanks guys - all useful info.