# Why does current flow direction matter in welding?

In DC welding, there are two configurations - direct current electrode positive (DCEP) and direct current electrode negative (DCEN). When the electrode is negative, the current flows from electrode to the workpiece. When the electrode is positive, current flows from workpiece to electrode.

It is said that in DCEN, 1/3 of the arc heat is produced in the electrode, and 2/3 at the workpiece.

Why is there such a difference? Why does the current direction matter here? I would intuitively assume that current is current and the direction it flows through the arc does not matter.

• In a lot of circuit analysis interchange electron current and conventional (hole) current but when you're talking about arcs and things like vacuum tubes, there is nothing abstract flowing in the opposite direction since it's empty space. In these cases, electrons are being "fired" from one surface to another. I guess if you use a cannon analogy it would make more sense that the positive electrode in the arc heats up more. Commented Sep 5, 2022 at 20:52
• This might be a good, interesting topic to post in physics.stackexchange.com Commented Sep 5, 2022 at 20:57
• Arcs are plasma not just electrons. That gives you positive ions travelling in one direction, negative ions and possibly free electrons in the other. Often (MIG, TIG) an inert gas (the IG) is used : the choice of gas will affect the polarity and mass of the ions and the energy they carry.
– user16324
Commented Sep 5, 2022 at 21:47
• The reason is two-fold: (1) the positive workpiece is heating due to the electron thermal energy in the plasma it is absorbing, while this same energy actually cools the negative electrode; and (2) the positive workpiece's thermionic work function also contributes heat to the positive workpiece, while again cooling the negative electrode. That said, both are heated by their respective fall-space voltages times the arc current. But note that the fall-space voltages are different for anode and cathode. Your question is good (+1) as these are still active topics in research literature.
– jonk
Commented Sep 6, 2022 at 0:24
• If you want to study the topic, I can refer you to a number of key papers on the topic. Some of these go back to 1982 (so far as I'm aware right now.) But more recently, even in 2020 and probably still later, there are new papers covering still more about all this -- especially because of applying SMAW in underwater situations where everything matters. (I do SMAW, MIG and TIG welding, myself, by the way.)
– jonk
Commented Sep 6, 2022 at 0:27