why the weld marks are black

Let’s  analyze why the weld marks appear black. The reasons are as follows:

1. The welding wire or aluminum alloy pipe is not clean and contains impurities.

2. The porcelain nozzle, chuck, and flow guide have been used for a long time and contain impurities, resulting in uneven flow distribution.

3. Argon gas is impure

4. The cleaning effect is not adjusted well.

5. The welding gun is broken and leaks air.

6. The machine is broken

Can we clean the black weld, yes we can, do as below: