[Jason72]

Hi everyone..
I was wondering if anyone can explain how the cleaning action on aluminum happens, when mig DC welding aluminum?

Thanks jason

[Oscar]

DCEP. That means the work itself is DC Negative. That means the electric arc emanates from the work, and shoots up into the consumable wire. Since the electrons are continually leaving the work part/surface, they are continually cleaning/etching the surface.

[tweake]

http://www.esabna.com/euweb/awtc/lesson2_12.htm

"2.3.2.4 Aluminum and magnesium are two metals that have a heavy oxide coating that acts as an insulator and must be removed before successful welding can take place. Welding with electrode positive provides a good oxide cleaning action in the arc. If we were to study the physics of the welding arc, we find that the electric current causes the shielding gas atoms to lose some of their electrons. Since electrons are negatively charged, these gas atoms now are unbalanced and have an excessive positive charge. As we learned in Lesson I, unlike charges attract. These positively charged atoms (or positive ions as they are known in chemical terminology) are attracted to the negative pole, in this case the work, at high velocity. Upon striking the work surface, they dislodge the oxide coating permitting good electrical conductivity for the maintenance of the arc, and eliminate the impurities in the weld metal that could be caused by these oxides."

in simple terms DCEP ions blast the oxide off the metal.
its ions coming down onto the metal rather than electrons going up that does the job.

[Oscar]

Interesting, I could have sworn I read it was the other way around, with the electrons doing the work. What I'm interested in now, is where they go afterwards.

[Bill Beauregard]

I've seen it both ways. Electrons erupting from the oxide coated welded object will blast off oxides, or conversely, positive ions sandblast it off.

My brain easier accepts the electrons lifting the oxide in the flow from work to electron.

My severely limited MIG aluminum experience: I have observed cathodic cleaning while using a spool gun. Yes it works.

[MinnesotaDave]

Interesting, I could have sworn I read it was the other way around, with the electrons doing the work. What I'm interested in now, is where they go afterwards.

Good news, the positive ions explain why many welders are so cranky

Screenshot_2018-02-01-06-06-09_kindlephoto-377995492.png (86.65 KiB) Viewed 1465 times

[Bill Beauregard]

Interesting, I could have sworn I read it was the other way around, with the electrons doing the work. What I'm interested in now, is where they go afterwards.

Good news, the positive ions explain why many welders are so cranky

Screenshot_2018-02-01-06-06-09_kindlephoto-377995492.png

Thank you so much for that Dave. Now go try to find some pictures of pretty girls to post.

Willie

[LtBadd]

Good news, the positive ions explain why many welders are so cranky

Screenshot_2018-02-01-06-06-09_kindlephoto-377995492.png

That's gotta be true!

[Bill Beauregard]

Ben Franklin guessed at the direction of flow of electrons. He randomly assigned positive as the state of surplus, flowing to deficit. In later tests he learned he had been wrong, electrons move the other direction.

Now we have arbitrarily assigned electrons negative flowing to a place of deficit. That's just backward!

Positive ions must be cheerful, or might negative ions be cheerful? I'm so confused.

Let's say negative electrons are negative only out of respect for Ben Franklin, who was wrong. They are really very optimistic particles. After they leave, nothing is left behind but positive, hostile ions, and like the positive Muslims who bomb everyone else, these happy/angry ions blow up $hit.

At any rate, it is during the half cycle when electrons rush from the work to the electrode that cathodic cleaning happens. As it takes a bit longer than 1/120 second for new aluminum oxides to form, we are able to weld aluminum.

Willie

[LtBadd]

1146614.png (44.74 KiB) Viewed 1449 times

[PeteM]

Good news, the positive ions explain why many welders are so cranky

Screenshot_2018-02-01-06-06-09_kindlephoto-377995492.png

Hahahahaa! That explains almost everything.

[tungstendipper]

Good news, the positive ions explain why many welders are so cranky

Screenshot_2018-02-01-06-06-09_kindlephoto-377995492.png

Hahahahaa! That explains almost everything.

I wonder how Dave grades his students before a storm?

[MinnesotaDave]

Good news, the positive ions explain why many welders are so cranky

Screenshot_2018-02-01-06-06-09_kindlephoto-377995492.png

Hahahahaa! That explains almost everything.

I wonder how Dave grades his students before a storm?

According to the positive ion theory, harshly...very harshly