With reverse welding polarity, they achieve higher penetrations

Welding equipment can work with alternating current or direct current. If these are alternating current, the working welding polarity is not distinguished since either cables or poles simultaneously alternate them.

However, when welding equipment has a direct current output, it works with direct polarity or reverses polarity. We will say that the polarity is direct when the electrode holder’s cable is connected to the welding machine’s negative pole. And on the contrary, we will say that it is reverse polarity when the electrode holder is connected to the welding machine’s positive pole.
These two polarities, direct polarity or reverse polarity, have different work characteristics as far as penetration is concerned in the welding beads they carry out. The direct welding polarity contributes more heat to the base material or piece, and the reverse polarity contributes more heat to the electrode.
Characteristics of each one
Direct polarity brings more heat to the base material to be welded. The particularity resides in the circulation of electrons in the circuit. In this case, the electrons circulate from the electrode to the part. Some direct polarity benefits are lower part deformations, higher weld feed, and narrower beads. This type of polarity is the most used with TIG welding, and coated electrodes such as rutile.
In reverse welding polarity, the electrons circulate from the part to the electrode, reaching, a higher temperature than the part. Some of the benefits of reverse polarity are that greater penetrations are achieved with basic electrodes and arc stability when welding with these electrodes. This type of polarity is rarely used for TIG welding except when welding aluminum.
Which polarity to choose?
Regarding welding with coated electrodes, it is advisable to do it with reverse polarity. With rutile electrodes, it is advisable to weld with direct polarity, although it is true that the latter also obtain good results with reverse polarity.
It is recommended to clear up doubts and do some tests with both electrodes and polarities, respecting the same electrode’s same adjustment parameters. It will almost certainly eliminate many of the doubts that may have arisen regardingwelding polarity.