How different or similar are E6010 (CSAE4310) and E6011 (CSAE4311) electrodes?

Let us start with the similarities. Both electrodes are all-purpose for piping, fabrication, repair, construction, and maintenance. Both can penetrate to rust, paint, and dirt (within reason), have relatively low deposition rates, and little slag that is easy to remove.

Their denomination tells us that both are E60XX electrodes, meaning that under standard condition both meet a tensile strength of 60 ksi. The “1” in the third digit indicates that they are “all position electrodes.”

Less obviously, both are cellulosic electrodes, descendants of the original trick of wrapping a bare steel rod in a newspaper and burning the newspaper together with the electrode. The main ingredient of newspaper is cellulose, which is still a key ingredient in E6010 and E6011.

Cellulose is an “organic compound,” which involves hydrogen. We all agree that hydrogen can do bad things in the welding of steel, such as cold cracking, however, when used wisely, hydrogen can be a friend. For reasons not completely well understood, hydrogen causes a much more concentrated arc, and that is the reason that E6010 and E6011 have a stiff arc with great penetration power… that’s the reason they can penetrate through paint and rust, and if you crank them up to “11”, they become cutting torches! Not only E6010 and E6011 use hydrogen to their advantage, it is also used occasionally in very high-tech plasma overlays to have a hotter, more concentrated arc.

Now, to the differences. They are few, but they matter enormously, and it all comes to plasma physics. Yes.

An amazing feat of arc welding is that the current jumps between the electrode and the plate through a gas… this is not common outside arc welding! It happens only because once the arc is started, the gas gets so hot (hotter than the surface of the Sun), that the heat vibrations causes the gas to lose electrons, much like shaking an apple tree can make the apples fall. Those electrons are responsible of carrying the current between the electrode and the plate. The flow of current maintains the heat, and if we stop the current, the arc very quickly extinguishes. This applies to all forms of arc welding.

Welding fluxes contain “arc stabilizers,” which are chemical elements that lose their electrons relatively easily. These elements typically are in the 1st column of the periodic table, and have a lonely electron in its outer orbit, which is easy to lose. In E6010, the arc stabilizer is sodium, and in E6011 it is potassium (both in the first column, check them out!). That’s pretty much the biggest difference in the formulation between these electrodes, but the consequences are huge.

Sodium is a smaller atom, and holds to its outer electron tighter than potassium, which is larger, so the outer electron is farther away and it is looser. Because potassium loses its electron easier, it has more stabilizing power than sodium… so what?

In DC welding current, the difference between E6010 and E6011 is small, but in AC welding current, E6011 comes to the rescue. In AC the current is sometimes positive, and sometimes negative, which means that at some point the current is zero… and didn’t we say that the arc extinguishes without current?

When there is no current, the arc extinguishes, but not immediately, if we move from positive to negative (or the other way) fast enough, there might be enough remaining arc to keep going in the new polarity. Arc stabilizers are the ones in charge of keeping the arc alive. When the change happens at 60 Hz, which is our line frequency, potassium is up to the task and can keep the arc alive. Sodium reclaims its loose electron faster and the arc extinguishes.

The practical consequence of arc stability is that E6011 can use transformer-type “buzz boxes,” which are very inexpensive welding machines, while E6010 requires rectifiers which are more expensive. Not surprisingly, E6011 is popular in South America, while E6010 is popular in the rich oil and gas industry in North America. My first welds were with E6011 in Argentina.

Why not then always use E6011? In addition to differences in arc stability, there are also subtle differences in their chemical behavior. E6010 slag is easier to handle than E6011, which is much helpful when doing root passes in pipes. There are claims that 6010 has a slightly higher deposition rate, which would be consistent with what we have seen with other flux systems in our lab. I do not expect this difference to be significant.

Now that we understand E6010 and E6011 in terms of arc stability and polarity, a good follow up question would be: “How is it possible that we use AC in GTAW of aluminum using only argon without any arc stabilizer?”

Welding is amazing.

Patricio Mendez
Professor
University of Alberta