Types of polarity in SMAW, MIG, MAG, FCAW, TIG and SAW

What is Welding Polarity and Polarity Effect on Welding?

Welding Polarity is the electrical circuit that is created when we turn on the welding machine (DC type) having a negative and a positive pole. Polarity is an important factor in the selection of the welding process for different materials. Choosing the right polarity affects the appearance, strength and quality of the weld. A wrong polarity selection will result into high spatters, insufficient or excessive penetration, & a lack of control of your welding arc. 

Types of Welding Polarity/ Current in SMAW, GTAW, FCAW & GMAW

The three different types of current or polarity used for welding are:

  1. Alternating current (AC),
  2. Direct-current electrode negative (DCEN) also called straight Polarity.
  3. Direct current electrode positive also called DCEP and Reverse Polarity.

What is Direct Current Electrode Negative or DCEN Polarity?

DCEN or also known as straight polarity works with the electrode connected to the negative, and the work is connected to the positive terminal as shown in the below picture (left side). The electrons flow from the Cathode (Welding electrode) to the Anode (workpiece). This gives around 1/3 of the welding heat on the welding rod and 2/3 on the base material being welded. Straight polarity due to the above reason results in high welding rod melting. DCEN is used in GTAW/ TIG welding as well as some limited applications in shielded metal arc welding. DCEP heats the electrode much more than DCEN in TIG welding; thus, DCEP is rarely used in the TIG Welding process.

What is Direct Current Electrode Positive or DCEP Polarity?

DCEP is also called Reverse Polarity. In DCEP as you can see in the above picture- the job is connected to the negative terminal and the welding rod is connected to the positive terminal. The electrons flow from the base material to the welding rod (cathode to anode flow of electrons). Change in these terminal points as stated above results in 2/3 heat concentration on the welding rod and 1/3 on the base material to be welded. DCEP is used in SMAW, GMAW (MIG/MAG, FCAW), and SAW welding processes. Due to high heat at the electrode end, DCEP results in a higher melt-off of the filler wire or electrode thus yielding in higher weld deposit compared to DCEN.

What is Alternating Current (AC) Polarity?

Alternating Current (AC) polarity uses alternating current and hence there are no negative or positive terminals. The electron flows keep alternating every 1/120 of seconds from the welding rod to the base material. AC polarity with alternating terminals brings cleaning action to the workpiece. This action is highly beneficial for welding materials having tough oxide layers such as aluminum & magnesium alloys welding.

Effect of Welding Polarity on Penetration & Heat Distribution in Welding

In GMAW, if we keep the electrode negative, the arc will become unstable, and the spatter is excessive as well as less heat on the welding wire, thus low melt-off rate. Similarly, in GTAW, if we keep the tungsten electrode positive, it will lead to the melting of the tungsten electrode fast. This can cause tungsten inclusion in the weld as well as other welding defects. Thus, a correct selection of the welding polarity is very important. The effect of welding polarity and heat distribution is shown in the below figure.

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