What Is Welding Electrodes?- A Complete Guide

What are welding electrodes?

Welding electrodes are lengths of wire connected to your welding machine. The current passes through the wire and creates an arc, which generates tremendous heat to melt and fuse metal together for welding.

An electrode is a coated metal wire. The electrode is made of materials similar to that of the metal you are welding. First, there are consumable and non consumable electrodes.

In shield metal arc welding (SMAW), also known as a stick, consumable electrodes are used, meaning that the electrode is consumed or becomes a part of the weld during use, and melts with the weld.

In tungsten inert gas welding (TIG), non-consumable electrodes are used, so they do not melt and become part of the weld. With gas metal arc welding (GMAW), also known as MIG welding, electrodes would be continuously fed wire and for flux-cored arc welding, you need a continuously fed consumable tubular electrode containing flux.

MORE: What is Welding?

How To Choose Welding Electrodes?

Stick electrodes are produced in a variety of forms, each form providing differing mechanical properties and requiring a specific type of welding power source. When selecting welding rods there are several things to consider:

1. Base metal properties
2. Tensile strength
3. Welding current
4. Base metal thickness, shape and joint fit-up
5. Welding position
6. Specification and service conditions
7. Environmental job conditions

Before you power up your machine and pick up your electrode holder, learn more about each of these factors.

Base metal properties

When selecting an electrode, the very first step is to identify the base metal composition. The objective is to match (or closely match) the electrode composition to the base metal type, which will in turn promote solid welds. If you are unsure of the base metal composition, consider the following questions:

• What color is the metal? If you’re working with a broken part or component, look for a rough and gritty internal surface, which usually indicates that the base metal is cast.
• Is the metal magnetic? If the base metal is magnetic, there is a good chance that the base metal is carbon steel or alloy steel. If the metal is not magnetic, it could be manganese steel, 300 series austenitic stainless steel, or a non-ferrous metals such as aluminum, brass, copper, or titanium.
• What do the sparks look like when you touch the metal with a grinder? Generally, the more flare (expanding) the sparks have, the more carbon the metal contains, as in A-36 grade steel.

When a chisel is used, does it bite (bite) into the base metal or bounce off? A chisel will bite into softer metals such as mild steel or aluminum, but it will bounce off harder metals like high carbon steel, chrome-moly or cast iron.

Tensile strength

In order to prevent welding discontinuities such as cracks, you want the minimum tensile strength of the electrode to match the tensile strength of the base metal.

To establish the tensile strength of stick electrode for the welding arc process, look at the first two digits of the AWS classification printed on the side of the electrode.

In the example, the E6011 electrode has a “60,” meaning that the filler metal creates a weld bead with a minimum tensile strength of 60,000 psi, which should work well with steel of similar min tensile strength.

Welding current

Some electrodes are used only in alternate current or direct current power sources and others could be used in either form. To determine current type, observe the fourth digit for variety of coating and the type of current and fill agreement while reviewing the AWS classification, (ASW, etc).

The type of current also affects the penetration profile of the weld is being created. A DCEP compatible electrode, such as E6010, will achieve deep penetration and allows for an extremely tight arc.

It even has the capability of “digging” through rust, oil, paint, and dirt. A DCEW compatible electrode, such as E6012, achieves mild penetration and does well on bridging two joints, or accomplishing a high speed high current fillet weld in the horizontal position.

Alternatively, an AC compatible electrode, such as E6013, achieves a soft arc with medium penetration and should only be used for welding clean, new sheet metal.

Base metal thickness, shape and joint fit-up

Thick materials necessitate an electrode with exceptional ductility and low hydrogen to avoid weld cracking. Electrode with AWS classification numbers ending in 15,16, or 18 are of exceptional low–hydrogen with a good toughness (high impact values) to deal with residual stress.

Thin materials require an electrode that produces soft arcs such as a 6013. Smaller diameter electrodes also have shallow penetration and help prevent burn-through by keeping the heat input lower.

You will also want to evaluate the joint design and fit-up as well. If you have a joint with a tight fit-up or one that is not beveled, you will want to use an electrode that offers a digging arc for adequate penetration, such as an E6010 or E6011.

If you’re working on materials with wide root openings, an electrode such as an E6012 will result in a concave weld face to bridge the gaps when making groove welds.

Welding position

The third digit in the AWS classification denotes the various position(s) the electrode is qualified for. Below are the respective positions that each digit refers to:

• 1 = Flat, horizontal, vertical and overhead.
• 2 = Flat and horizontal only.

As an example, an electrode that is AWS classification 7018 can be used in flat, horizontal, vertical, and overhead positions.

Specification and service conditions

You should also assess the conditions the welded component is likely to experience during service. If it is going to be used in an environment with high temperatures or low temperature and subjected to repetitive shock loading, a low hydrogen electrode with improved ductility will minimize the potential for weld cracking.

In addition, you should definitely check for the existence of welding specifications if you are doing any critical applications such as pressure vessel or boiler fabrication. In most cases, these welding specifications will specify the type of electrodes that need to be used.

Environmental job conditions

To ensure maximum performance, you should always clean your base metals of excess mill scale, rust, moisture, paint, and grease. Clean base metals help prevent porosity, and allow for increased travel speeds.

Minimize cleaning of the base metal, E6010 or E6011 electrodes deliver a deeply penetrating arc and will penetrate contaminants.

How To Read The Code On Stick Electrodes?

The American Welding Society (AWS) has a numbering system that will provide information about a particular electrode, for example, the application it is most suitable for and how to operate it for maximum effectiveness.

Digit	Type of Coating	Welding Current
0	High cellulose sodium	DC+
1	High cellulose potassium	AC, DC+ or DC-
2	High titania sodium	AC, DC-
3	High titania potassium	AC, DC+
4	Iron powder, titania	AC, DC+ or DC-
5	Low hydrogen sodium	DC+
6	Low hydrogen potassium	AC, DC+
7	High iron oxide, potassium powder	AC, DC+ or DC-
8	Low hydrogen potassium, iron powder	AC, DC+ or DC-

The “E” denotes an arc welding electrode. The first two digits of a 4-digit number and the first three digits of a 5-digit number indicate tensile strength. For example, E6010 means 60,000 pounds per square inch (PSI) tensile strength, and E10018 means 100,000 psi tensile strength.

The next to last digit indicates position. So, the “1” stands for an all-position electrode, the “2” for a flat and horizontal electrode, and the “4” for a flat, horizontal, vertical down and overhead electrode. The last two digits indicate the type of coating and the welding current.

E	60	1	10
Electrode	Tensile Strength	Position	Type of Coating & Current

What is the welding electrode coating?

Electrode coatings should not only provide gas shielding for the arc, allow easy striking and arc stability, allow for a protective slag, allow for good weld shape, but most importantly provide sufficient gas shielding from oxygen that is present during the moment of releasing the heat form the weld to the surrounding areas.

There are several available electrode types; often these types are classified by the coating.

Electrode Coating is an electrode which has a comparatively good coating deposited around it in a coating thickness of 1 to 3mm. The coated weight can be between 15 to 35% of the weight of the electrode.

Most fabrication is carried out using coated electrodes, and the procedure limits the operation to a slow manual operation. If the flux coating is in a long tube, the electrode can be in the form of an uncoated wire in the form of a coil.

Then we can completely automate and make the shielded arc process continuous. The only purpose of a light coating is to stabilize the arc; the coating is also called an ionizing coating. Because the electrode coating is brittle only straight-stick electrodes can be used.

The function of Electrode coatings

• By ionizing the path of the arc, improving the arc stability by supplying chemicals that have this capability
• Provide a protective gaseous environment to stop molten metal picking up oxygen, hydrogen and nitrogen
• Provide protective slag over hot metal
• Provide flux, which is useful for removing oxides and other impurities from the molten metals
• Reduce spatter of weld metal – when the coating does not burn off as fast as the core
• Acts as deoxidizer
• Slows cooling rate of weld (due to the layer of slag over weld, it slows the cooling down to make it not harden as quickly)
• Coatings are usually insulators of electricity and therefore available for welding electrodes in narrow grooves, etc.

Types of Coatings:

Even though there are common characteristics in every type of electrode coating, each coating’s distinct chemical composition will give different properties. Make sure to research the best applications for each coating so you choose a coating to suit your project.

Cellulose:

These coatings are about one-third cellulose and the other two-thirds made of other organic materials. The welding arc will decompose the materials creating three individual gases; hydrogen, carbon monoxide, and carbon dioxide which enhance the arc. The strengthened current in turn penetrates the metal, resulting in high strength welds.

Also transparent to the welder’s eye, cellulose coatings create an additional layer of gas to protect weld pools from contaminants.

The gas layer creates a separation between the metals being welded and other environmental elements like oxygen, nitrogen, and hydrogen that could be absorbed by the welds and create porosity.

Porosity can be harmful by poisoning a good weld, thus using an electrode with a cellulose coating can improve weld quality.

There are many different cellulose coatings that are each made with a specific chemical combination giving each coating specific attributes and best practices. The cellulose content of the base recipe is a general rule, however, the additional organic materials vary greatly.

Mineral:

Mineral coatings develop a layer of slag over the weld. While the slag may seem like a nuisance, it does have its benefits. The slag created by the mineral-coated electrode cools much more slowly than that of a cellulose-coated electrode, as does the welded material underneath.

This allows time for the impurities in the metal to float to the surface and not be trapped in the weld and compromise its structural integrity.

Mixture:

Electrode coatings with minerals and cellulose are a favorite among manufacturers because they offer the advantages of both materials.

One of the benefits of these coatings is that there can be anywhere from a few to more than ten components which by virtue of chemical variety your coatings offer you a number of significant advantages.

Using both shielding gas and protective slag cover on a weld can be particularly valuable when welding with very difficult base metals.

Most Common Electrode Coatings:

While there are certain applications requiring specific electrode coatings and characteristics, these are five of the most common welding electrode coatings you’re likely to see.

Cellulose Electrodes:

Cellulose electrodes are best used in the vertical position but leave a very thin, and easy to remove layer of slag. They break down into hydrogen and carbon dioxide as they are heated. This gives a good protective gas layer above the weld pool.

This can also, however, expose the weld to hydrogen embrittlement. In their purest form a cellulose coating best utilizes DC but with some other elements, it may be possible to use AC. Cellulose electrodes give you all the ease of rutile coatings but deeper penetration and less irritating slag.

Rutile Electrodes:

Virtually the same as cellulose, the only difference being that rutile contains a higher proportion of titanium dioxide, forming a gas shield of oxygen, nitrogen, carbon and hydrogen, making rutile electrodes ideal for welding low-carbon steel.

However, slag on rutile electrodes can tend to impart titanium traces in the deposited metal. When cellulose is added to rutile electrode coatings, it provides additional protection over the weld pool. These electrodes give off lower spatter and fume emissions, and can be used in all positions.

Iron Oxide Electrodes:

Iron oxide electrodes can be used with AC and DC and result in slag that is relatively easy to remove from the weld. The coating on this electrode is oxygen-rich, which can lead to weld deposits that are lower in overall strength.

However, the risk of hydrogen embrittlement is much lower than with cellulose electrodes. Iron oxide electrodes provide good arc control and give neat, accurate bead placement.

Basic Electrodes:

Also known as hydrogen-controlled electrodes, these electrodes require increased maintenance before welding. Electrodes must be stored in the dry and baked.

Not following these maintenance requirements may create an unstable chemical composition in the coating during the welding process and will subsequently give you a compromised weld structure.

A basic electrode produces a low and controlled level of hydrogen, thus minimizing the risk of porosity and cracking in a weld. These electrodes are a great alternative when dealing with steel when treated and stored properly.

Iron Powder Electrodes:

These electrodes are modifications of other electrode coatings incorporating iron powder into the mix. Metal powders are being added to electrode coating mixes more frequently, as they can make the welding process more efficient while improving weld quality.

Iron power electrodes are an extension of cellulose electrodes, where the electrodes are capable of being used for welding when supplying alternating current.

If you are working with welding that utilizes separately coated electrodes, you would do well to learn and understand the different options available, as this can make or break a project.

When you decide to use an electrode, remember that additional factors position, tensile strength, and core metals, must be considered.

types of welding electrodes

Welding rods used in MIG and stick welding are examples of consumable electrodes. They contain filler material that melts to make weld joints.

TIG welding uses non-consumable electrodes. Non-consumable electrodes consist of mostly tungsten, which due to its high melting point does not melt (unlike consumable electrodes) and only supplies an electric arc while welding. The filler material is supplied with a wire that is supplied manually.

Thus the difference between these two electrodes is that consumable electrodes melt while non-consumable electrodes do not.

Both of these categories contain several different types of electrodes.

Consumable electrodes

Consumable electrodes are fundamental to stick, MIG, and flux-cored arc welding. The consumable electrodes for stick welding are termed stick electrodes. Stick electrodes can be heavy-coated, shielded arc, and light-coated.

1. Light-coated electrodes

As implied by the title, light-coated electrodes have a thin layer of coating on their surface, typically applied by spraying and/or brushing.

The electrodes and their coatings can be made from various materials. The filler material is often very similar to the base metal that is being welded.

The light coating provides another crucial purpose as well. The coating minimizes impurities, for example, sulfur and oxide, so that a better-quality weld can be made.

The coating also allows the filler material to melt more uniformly so that you can produce a flatter, smoother, and consistent weld bead form.

Because the coating is thin, an acceptable amount of slag is created. Shielded arc electrodes are similar to light-coated electrodes in that they are often made from different materials.

The principal difference is that shielded arc electrodes have thicker coatings. They are intended for heavier welding applications, for example, cast iron welding.

2. Bare electrodes

Bare electrodes can be a little challenging to work with because the arc is somewhat uncontrollable and unstable in nature. The light coating helps to stabilize the arc, which allows for better control concerning the weld. Bare electrodes have limited use; for instance, the only known use is for welding manganese steel.

3. Shielded arc electrodes

Shielded arc electrodes have three different kinds of coatings to accomplish various objectives. One coating has cellulose in it and utilizes a protective gas layer to protect the weld area. The second coating has minerals that generate slag. And, the last coating has both minerals and cellulose.

Shielded arc electrodes create a protective gas layer that acts as an efficient barrier to safeguard the hot weld area from contamination and corrosion caused by air exposure.

This makes it easier to make stronger and more reliable welds. It is important to protect the heated weld area from interrupting atmospheric gases, like nitrogen and oxygen.

These gases combine with the molten weld metal (2000 degrees Celsius) which creates brittle, porous, and weak welds.

Shielded arc electrodes reduce sulfur, oxides, and other forms of contamination within the base metal to provide consistent, smooth, and clean welds.

Coated electrodes also produce a more stable electric arc than bare electrodes making it easier to through welding with less spatter.

Shielded arc electrodes produce slag from the mineral coating. The slag may initially seem bothersome to remove, and wasteful, but it has a useful purpose.

The slag cools much slower than the shielded arc electrodes, and draws impurities out of the pool and to the surface due to the slow cooling. Therefore, you will end up with quality welds. The welds will be relatively clean, not perfect, durable, and strong.

Non-consumable electrodes

Non-consumable electrodes are simpler to understand not only because they do not melt but also because there are only two types.

1. Carbon electrodes

The carbon electrode, used for both welding and cutting, is the first type. It is made of carbon graphite, and may have a thin layer of copper or may be bare if desired.

The American Welding Society has not issued any standards for this type of electrodes. However, there are military specifications for carbon electrodes.

2. Tungsten electrodes and their different kinds

The second type of non-consumable electrode is the tungsten electrode, which is used for the TIG welding process.

The kinds of tungsten electrode that can be used are: pure tungsten electrodes (they have green markings), tungsten electrodes containing 0.3 to 0.5 percent zirconium (these have brown markings), tungsten electrodes that have 2% thorium content (these have red markings) and tungsten electrodes containing 1 percent thorium (these have yellow).

The most notable non-consumable electrode type, pure tungsten electrodes, will not be a very effective choice, as they are mainly used for lighter welding purposes based on two factors.

• 1. Pure tungsten does not hold up as well, nor is as strong as tungsten alloys (meaning they do not last long), and
• 2. Pure tungsten is more likely to have problems with high currents.

As a result, tungsten electrodes that do contain zirconium (0.3 to 0.5 %) have pretty good results with alternating currents, and they do extend the performance of pure tungsten; however, tungsten electrodes with thorium perform even further and have a better arc stability than those containing zirconium.

Electrodes that are tungsten with 1% to 2% thorium are an ideal electrode choice and one of the most common non-consumable electrodes used in arts and industries as they last longer and allow higher current than pure tungsten electrodes, giving more arc control and starting.

When using tungsten electrodes that are flux, it is suggested that you try to use the most current that is possible, if it is a plain cylindrical, so that it is easy to control the arc and keep it going.

Otherwise, if you don’t use enough current, it can be difficult and require more effort to sustain the arc and control it with less current, so you can try to use the maximum current as allowed.

If an arc is difficult to control, then tapering of the end (making a conical tip) of the tungsten will help to keep a better arc expression and control. In the case of tapering the tungsten and using touch-starting you will need to use a DC welding machine.

Keep in mind that if you taper the tungsten electrode, that tungsten electrodes with thorium and zirconium have better longevity/durability than pure tungsten electrodes, it makes sense to consider the touch-start if you make tapered tungsten electrodes.

FAQs