problems welding .250 aluminum

[sandfish]

ok so i have never had this issue before but everytime i start to lay a bead black crap keeps coming out of the metal. ive ground it down cleaned it with brake cleaner and acetone and used a stainless brush on it before welding i even purged it with 8 pounds of argon..still contaminents keep puking out. is it the aluminum itself or the rod or me? the material is 2x2 .250 6061 and the rod is 1/8 4043. what am i doin wrong here?

[SPONSOR]

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