Hello again katrutro, I don't know exactly what all of the results of using the 75/25 gas will be. What I do know is that the wire was designed to be used with 100% CO2, most likely and mainly for a cost savings on the shielding gas. The additives that I was speaking of are there to allow for the use of the CO2 shielding(the CO2 isn't inert so it will allow some of these additives to react with the shielding gas and not become a part of the finished weld metal in the same form) and are designed to provide certain actions in the arc and the weld puddle which will provide the proper finished weld deposit characteristics. Using the argon mixed gas will not allow the flux additives to do the things that they were designed to do(this is due to the inert portion of the shielding gas provided by the argon part) and then the weld deposit will not meet the criteria that is given in the wire's specifications. Hope this explained it a bit better. Regards, aevald

Katrutro: The inertness of the argon is where the differences come from. The wire has an extra ammount of some of the elements based on the fact that some will be lost due to the active nature of the CO2. Using the C25 in place of it will give too much of those elements, and this has the potential to change the weld metal properties.