Welding Electrodes: Welding Rod Sizes and Uses

Whether you are a professional welder, home hobbyist, or beginner interested in a full-time welding career, welding electrodes will take center stage in your welding projects. Because of their essential role, you should know which electrode type to use for various jobs.

Here is what you need to know about electrodes so that you always choose the right one for each application:

What are welding electrodes?

An electrode is a coated metal wire made of similar materials to the base metal. Welding electrodes are wire lengths connected to your welding machine to create an electric arc when an electrical current passes through them, and the arc generates enough heat to melt and fuse the metals.

There are two main welding electrode types: consumable and non-consumable. In stick welding, a.k.a. shield metal arc welding (SMAW), the electrodes are consumable, used during welding, and melt into the weld. On the other hand, tungsten inert gas welding (TIG) electrodes, typically made of tungsten, are non-consumable and do not melt into the weld.

Gas metal arc welding (GMAW), or MIG welding as it’s usually called, uses continuously-fed wire as electrodes. At the same time, flux-cored arc welding also has a continuously-fed consumable wire, but it’s a tubular electrode containing a flux.

Selecting the Right Electrode

Choosing an electrode is determined by the requirements of the welding job. These include:

• Strength: Ensures the electrode meets the required joint strength.
• Welding position: You have fewer choices of electrodes, depending on your welding position: overhead, horizontal, vertical, and flat.
• Power Supply: You can’t use a rod that doesn’t run on your power supply.
• Joint Type: Factors include penetration, joint access for slag removal, material thickness, and surface cleanliness.
• Material: stick welding electrodes come in cast iron, high carbon steel, mild steel, iron-free (nonferrous), and special alloys.

What are the different types of welding rods, and the ideal applications for each type?

Consumable electrodes are used in stick, MIG, and flux-cored arc welding, and the stick electrodes are further divided into heavy-coated (shielded arc) and light-coated electrodes.

Heavy-coated electrodes: As the name suggests, these electrodes have a thicker coating applied by dipping or extrusion. They are manufactured in three types: those cellulose coatings, mineral coatings, or a combination. Cellulose-coated electrodes protect the molten metal with a gaseous zone around the weld zone, while mineral-coated electrodes form a slag deposit. Heavy-coated electrodes are recommended for welding steels, cast iron, and hard surfacing. 

Light-coated electrodes: The light coatings reduce impurities, help make the metal more uniform, increase arc stability, and produce a thin slag.

What do the numbers on welding rods mean?

Among the numerous things you will need to learn when you begin stick welding is distinguishing one stick electrode from another. You can determine what type of stick welding electrode you have by learning a few numbers and letters printed on the base of the electrode. 

Every stick electrode is unique,e with some working well on rusty metal while others require clean steel. Some are good for any welding position,n but others are restricted to flat welding. Identifying a stick electrode is relatively easy when you know how to interpret the four or 5-digit alphanumerical code that tells you what you need to know.

Here is an example of a welding rod number:

E7018

The first letter stands for “electrode,” the consumable, conductive part of the welding circuit creating the arc.

The first two numbers identify the tensile strength of the electrode’s filler material. The tensile strength is given in thousand pounds per square inch reading, so this electrode would contain 70,000 lb. or be identified as 70. The tensile strength of a material refers to the maximum amount of tensile stress it can withstand before failing.

The third digit on the electrode identification number is 1, indicating that this electrode is suitable for all welding positions. If the number were a 2, that would tell you this electrode is appropriate for flat and horizontal welding only. And skipping the number 3, a number 4 identifies the electrode as correct for welding only flat, horizontal, vertical down, and overhead positions.

The fourth numerical digit in the electrode identification number indicates coating type and current. The following table explains:

Digit	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 electrode identification number tells you that the electrode (E) has 70,000 pounds of tensile strength (70) and is suitable for all welding positions (1). From the chart above, the coating is low hydrogen potassium and iron powder with AC, DC, or DC- welding currents.

What are the standard rod sizes, and how are they determined?

The most common stick rod diameters are 3/32″, 1/8″, and 5/32,” and these sizes will cover most of your welding projects. However, it would be best if you understood how the selections of these rod sizes relate to the base metal thicknesses and the part they play in achieving a professional-quality weld.

For example, smaller diameter rods--such as 1/16” and 5/64”-- are more complicated to work with than common-size rods. These rods are designed for workpieces thinner than 1/8″, but 1/8” is the thinnest material recommended for stick welding. Rods smaller than 1/8” tend to vibrate at the tip, requiring a steady hand. Also, they are more challenging to find and cost more.

Stick rods 3/16″ and larger are also more challenging to use. They are for the thickest and largest workpieces and require significant experience to get a good weld. They also create large puddles that are hard to control. You will need a welding machine that can output a high amperage, and as the rods get bigger, so do the hazards. More heat, UV rays, fumes, spatter, and noise equal a safety issue.

Base metal thickness

As a rule, you would select a rod that is a size thinner than the base metal. For example, if the base metal thickness is 1/8″, use a 3/32″ rod. This works well on thicknesses up to 3/16” and for standard welds like a one-side single-pass butt weld.

Of course, this rule is not hard and fast since many welding professionals select a rod diameter that is half as thick as the base metal, and they get excellent results. However, if you go with a rod much thinner than that, you risk having a low metal deposition rate.

Choosing a rod with the same diameter as the base metal’s thickness could cause the heat to blow through the metal and create excessive warping. Some novice welders mistakenly pick a rod thicker than the base metal, resulting in too much heat in the joint, making welding nearly impossible.

One exception to the rule applies to very thin metals. For instance, if you are welding 17-gauge (1.4mm) sheet metal, the smallest rod would be 1/16″ (1.6 mm). However, stick welding thin metals is challenging, requiring much experience and giving unsatisfactory results. Veteran welders sometimes use thicker rods on thinner metals since narrow rod diameters are harder to find and costlier.

Also, when the base metal is thicker than 3/16″, it helps to bevel the joint for full penetration and weld it with common-sized rods.

Final thoughts

Deciding on the right electrode for stick welding is relatively straightforward if you remember a few suggestions:

• Consider the type of welding and the base material
• Know what the electrode numbers represent. For example, a 6011-rod number will have a minimum of 60,000 pounds of tensile strength per square inch of weld. 
• The last two digits of the rod number refer to the flux coating on the rod, with higher numbers representing more shielding and more flux or metal being deposited.
• A 6011 electrode is used for standard maintenance and can be used in all welding positions, works on dirty metals, and tolerates an imperfect joint.