Mig Welding Aluminum Problem – Black Powder Residue
I had a struggle recently trying to solve a mig welding aluminum problem. I do a lot of aluminum mig welding, primarily with 4043 wire and always wonder, what is that black powdery residue on the edges of the weld? Was it soot? If so, where would the carbon be coming from? Was the argon sucking in carbon dioxide from the atmosphere (venturi principle) and contaminating the weld?