Tips for selecting tungsten Electrodes – What Do Different Colors and Types Represent [TIG Welding]

About Tungsten rods

Tungsten is a rare metallic element with the highest melting point of any metal, 3,410 degrees Celsius. The positive characteristic of tungsten makes it a foundation of Tungsten Inert Gas (TIG) welding.

Non-consumable electrodes come in a variety of sizes, electrode diameters, and lengths. In addition, they can be composed of either pure tungsten or a hybrid of tungsten and other rare earth elements and oxides.

The proper electrode selection depends on many variables, including the type of weld, the composition of the material being welded, and the amperage level, among other factors. Luckily, each tungsten stick has a color code applied to one end, which identifies the material type of the tungsten.

The American Welding Society document AWS A5.12M/A5.12:2009 provides a table that identifies the color-coding used in the United States, Europe, and Japan, representing the bulk of the market share of sold tungsten.

Let’s take a look at the types and uses.

Pure Tungsten electrodes – EWP

[Code Color: Green]

Pure tungsten electrodes, as their name states, contain 99.50% tungsten. As a result, they provide the highest consumption rate of all electrodes.

These electrodes form a clean, balled tip when heated and result in good arc stability in AC welding. In addition, they offer a stable arc in balanced wave and sine wave welding, especially when dealing with aluminum and magnesium.

Besides the increased consumption, arc start is somewhat harder compared to thoriated or ceriated electrodes.

However, the pure tungsten electrode is typically less expensive than its alloyed counterparts, making it a popular choice. Nonetheless, pure tungsten electrodes tend to spit at a higher amperage, and they are not to be used for TIG welding in the DC welding process. On the contrary, they work well on AC sine wave welding.

Thoriated Tungsten Electrode

Thoriated tungsten electrodes contain a minimum of 97.30% tungsten and 1.70 to 2.20% thorium. Thorium addition increases the electron emission qualities of the electrode, which improves arc start and allows for a higher current carrying capacity.

Good DC welding arc starts, and stability, medium erosion rate, medium amperage range, and medium tendency to spit makes the thoriated tungsten the most commonly used electrodes today. Even though they can be used for AC welding, thoriated electrodes are exceptional for DC electrode negative welding (straight polarity) on carbon and stainless steel, nickel alloys, and titanium welding performance.

However, keep in mind that thorium is radioactive, so you should be extra careful when grinding and preparing. Therefore, you should follow the instructions and Material Safety Data Sheet (MSDS).

Thoriated Electrode EWTh-1 (WTh 10)

[Code Color: Yellow]

These electrodes were designed for DC applications, as they contain 0.8–1.2 percent of thorium dispersed throughout their entire length. In addition, EWTh-1 electrodes maintain a sharpened point which suits welding steel.

EWTh-1 electrodes can be used on alternating current work, but a satisfactory balled end is difficult to maintain. Therefore they are not desirable for the welding of nonferrous material.

Thoriated Electrode EWTh-2 (WTh 20) 

[Code Color: Red]

Thoria content of 1.7–2.2 percent in the theEWTh-2 electrode improves operating characteristics. If they are aimed at alternating current welding, balling can be accomplished briefly and carefully welding with direct current electrode positive prior to welding with alternating current.

During alternating current welding, the balled end does not melt, so emission is not as good as a liquid ball on an EWP electrode.

Keep in mind that AWS classifies one more type of thoriated tungsten electrode, WTh 30, that carries a violet color code. However, this electrode has no commercial significance in the United States.

Ceriated Electrodes – EWCe-2

[Color Code: Gray, former Orange]

Ceriated tungsten electrodes contain about two percent cerium oxide (CeO2), referred to as ceria. Even though other grades of this electrode type are commercially practical, only one grade, EWCe-2, has been incorporated in this specification as having commercial significance.

The advantages of tungsten electrodes containing ceria, compared to pure tungsten, include increased ease of starting, improved arc stability, and reduced rate of vaporization or burn-off, and advantages increase with increased ceria content.

Like thorium, ceriated electrodes are best used to weld carbon steel and stainless steel, nickel alloys, and titanium. Therefore, we are discussing an obvious replacement for 2% thoriated electrodes.

Zirconiated Electrodes

Zirconiated tungsten electrodes contain a minimum of 99.10% tungsten and 0.15 to .40% zirconium.

These electrodes are suitable for AC welding as they have high resistance to weld contamination and can retain a balled tip.

You can use them when TIG welding aluminum alloys and magnesium alloys using inverter or transformer-based constant current power sources.

Compared to pure tungsten electrode, zirconiated tungsten electrode produces less spit, handles higher amperage, and provides better arc starts and arc stability.

 Zirconated Electrode EWZr-1 (WZr 3) 

[Color Code: Brown]

This tungsten electrode contains about 0.3%zirconium oxide, called zirconia. They are preferred for applications where tungsten weld puddle contamination must be minimized. Therefore it performs well when used with alternating current.

The AWS recognizes one more classification, EWZr-8 (WZr 8) Electrode, which carries a white color code. However, this zirconiated electrode has no commercial importance in the United States.

Lanthanated Tungsten Electrodes

EWLa-X electrodes are tungsten electrodes containing lanthanum oxide, referred to as lanthana.

Lanthanated electrodes are often considered as an alternative to thoriated electrodes since they show similar characteristics when using inverter or transformer-based AC or DC processes.

Lanthanated tungsten electrodes are best used in welding non-corroding steels, titanium alloys, nickel alloys, and copper alloys.

While they are similar to thoriated electrodes, lanthanum is not a radioactive element.

Lanthanated Electrode EWLa-1 (WLa 10)

[Code Color: Black]

EWLa 1 electrodes nominally contain 0.8-1.2 weight-percent (wt.-%) lanthanum oxide. The advantages and operating characteristics are very similar to EWCe-2 electrodes. Thus, they offer the best dc welding arc starts and stable arc, low erosion rate, wide amperage range, and no spitting.

Lanthanated Electrode EWLa-1.5 (WLa 15)

[Code Color: Gold]

EWLa-1.5 designates TIG electrodes containing 1.3–1.7 wt.-% dispersed lanthanum oxide (La2O3). The oxide enhances arc starting and stability, reduces tip erosion rate, and extends the current operating range. Lanthanated tungsten can be used for both DCEN and AC applications.

Lanthanted Electrode EWLa-2 (WLa 20)

[Code Color: Blue]

 EWLa-2 electrodes contain 1.8–2.2 wt.-% dispersed lanthanum oxide. Remember that these electrodes have the highest volume of oxides of any of the specific single-additive AWS-specified electrode types.

As mentioned above, oxides enhance arc starting and stability, reduce the tip of the electrode ware and extend the current operating range.

Rare earth tungsten electrodes (EWG)

The EWG electrodes contain an additive (rare earth oxides) not specified by an existing classification. The purpose of the addition is to enhance the nature or characteristics of the arc, as defined by the manufacturer.

Although no additive is specified, the manufacturer must identify any specific additions and the nominal quantities added.

Compared to other electrodes that are subject to AWS classification, the manufacturer may select any color not already in use.

These electrodes can be used for AC and DC welding processes, but you should read the details of each metal listed on the package. At their best, rare earth electrodes can ensure stable arc, longer life, and a current that rivals other electrodes, even though they are usually smaller.