The Basics of TIG Welding Current Types and Polarity Settings

To begin TIG welding machines are designed to produce a constant amperage at all times and that means when you set the machine it is set in terms of amperage settings. The amperage output while welding rarely changes. What does change is the voltage depending on the length of the arc. The arc is how the voltage is regulated. The voltage will increase when the arc length is increased and at the same time the voltage will decrease when the arc is shortened. Ultimately a TIG welding power supply will always stay consistent on the amperage setting!

TIG welders produce two types of current. They are D/C or direct current and A/C or alternating current. Alternating current is typically used for welding aluminum and magnesium. Outside of these two metals A/C is rarely used. D/C or direct current is used on most other metals. This includes steel, stainless steel, copper, copper nickel, and most of the exotic metals.

Direct current has two polarity types. The two polarities are DCEN or direct current electrode negative and DCEP or direct current electrode positive. What electrode (-) negative means is the TIG torch is the (-) negative side of the circuit or terminal. On the electrode (+) positive side it means the TIG torch is the positive side of the circuit or terminal. Direct current is the same current type that a car battery produces. The way D/C works is the electricity flows in one direction only. That is it flows from the (-) negative side to the (+) positive side. Just remember the (-) negative side is the losing side and the (+) positive side is the gaining side.

The way direct current polarity applies to TIG welding is how much heat is concentrated on the tungsten electrode. If the machine is set on DCEN or direct current electrode negative 2/3 of the heat is concentrated on the weld joint. DCEN is also one of the reasons tungsten is able to produce such a high temperature arc without melting! On DCEP or direct current electrode positive 2/3 of the heat is concentrated on the tungsten electrode.

The way this applies to TIG welding depends on the thickness of the metal welded. Most of the welding done with TIG is on DCEN because the metal is on the thicker side. Here you want the majority of the heat to be on the metal welded. For most welding applications just remember that you want the TIG torch to be the (-) negative side of the circuit. When it comes to welding very thin sheet metal you may want to consider switching over to DCEP or direct current electrode positive (+). This will put most of the heat onto the tungsten electrode and keep the arc from burning up the sheet metal. In the case of DCEP you want to weld using low amperage setting otherwise the tungsten will also burn up! There is one other case you would want to set the machine to DCEP and that is to shape the tungsten into a ball end. DCEP will start to melt tungsten very quickly on this setting and that is why it is used to create ball shaped tungsten ends.