A quick google search will tell you that most of them are constructed from 6061-T6. Another google search will tell you to use either 5356 or 4043 to weld 6061. 5356 is stronger but more crack sensitive. 4043 is weaker but more ductile.
I've seen the old boss do this numerous times and he always used 4043. In fact, the only time I ever saw him use anything other than 4043 was on a boat. Not sure what he used then. All i know is that i brought him 4043 and he said we couldn't use it on a boat. He went back and got what he needed. I didn't even know there was more than one type of aluminum filler wire back then.
Edit:
I don't believe that anyone makes 6061 rods but I could be wrong. That alloy's strength comes from the T6 temper and once heated to welding temperatures it isn't much stronger than pure aluminum unless it gets heat treated in a heat treat oven and is then properly quenched.
I've seen the old boss do this numerous times and he always used 4043. In fact, the only time I ever saw him use anything other than 4043 was on a boat. Not sure what he used then. All i know is that i brought him 4043 and he said we couldn't use it on a boat. He went back and got what he needed. I didn't even know there was more than one type of aluminum filler wire back then.
Edit:
I don't believe that anyone makes 6061 rods but I could be wrong. That alloy's strength comes from the T6 temper and once heated to welding temperatures it isn't much stronger than pure aluminum unless it gets heat treated in a heat treat oven and is then properly quenched.
Raymond
Everlast PowerTIG 255EXT
Everlast PowerTIG 255EXT