Which Group Of Electrodes Is Low Hydrogen Type

ByJim Boslice Metalworking & Fabrication

Low hydrogen electrodes are categorized under the EXX18 and EXX15/16 classifications, most notably the common E7018 rod.

These electrodes are designed to minimize hydrogen-induced cracking in high-strength steels and thick metal sections.

If you have ever stared at a pile of welding rods in a supply shop, you know how overwhelming the number codes can be. You want a strong, reliable bead, but you are worried about the integrity of your steel. Choosing the right consumable is the single most important decision you will make before striking your arc.

I have spent years in the shop fixing failed welds that were caused by nothing more than the wrong rod choice. It is frustrating to spend hours grinding out bad metal when a little bit of knowledge could have prevented the problem entirely.

In this guide, we are going to demystify the classification system so you can pick the right material for your next project. We will break down exactly which group of electrodes is low hydrogen type and why these specific rods are the gold standard for heavy-duty fabrication.

Understanding the E7018 and Which Group of Electrodes is Low Hydrogen Type

When you look at a welding rod box, the numbers are not random; they are a code from the American Welding Society (AWS). For the home shop hobbyist, the most critical distinction is between cellulosic rods and those designed to prevent cracking.

The EXX18 classification is the most common group that defines low hydrogen electrodes. These rods are formulated with mineral-based coatings that produce a very stable arc while shielding the molten puddle from atmospheric moisture.

If you are working on structural projects, trailer frames, or thick plate steel, you need to know which group of electrodes is low hydrogen type to ensure your weld doesn’t become brittle. Hydrogen is the enemy of strong steel, as it can hide in the weld metal and cause microscopic fissures over time.

Why Low Hydrogen Electrodes Matter for Your Workshop

You might be wondering why you shouldn’t just use a standard E6010 or E6011 rod for everything. While those rods are fantastic for penetrating dirty, rusty, or painted steel, they are not low hydrogen.

Low hydrogen electrodes are specifically engineered to keep moisture out of the arc. When water vapor breaks down in the heat of an arc, it releases hydrogen gas, which then diffuses into the cooling weld pool.

Preventing Cold Cracking

Cold cracking, also known as hydrogen-induced cracking, often happens hours or even days after the weld is finished. By using an EXX18 rod, you significantly reduce the risk of these hidden defects in high-strength or thick-walled materials.

Improving Weld Ductility

These rods provide excellent impact toughness, meaning the weld can absorb energy without snapping. This is vital for garage projects that will be subject to vibration or heavy loads, such as engine hoists or shop workbenches.

How to Identify and Store Low Hydrogen Rods

Identification is straightforward once you know the code. Look for the last digit in the four-number sequence, such as E7018. The number 8 indicates the electrode has a low hydrogen iron powder coating.

However, owning these rods is only half the battle. Because they are designed to be “low hydrogen,” they are extremely sensitive to humidity. If you leave them out on your workbench in a damp garage, they will absorb moisture from the air, rendering them useless for high-quality work.

  • Keep them sealed: Always store your rods in their original airtight container.
  • Use a rod oven: Professionals use specialized heating ovens to keep these rods bone-dry.
  • The DIY alternative: If you are a hobbyist, a simple airtight plastic storage tube with a desiccant pack helps, though a dedicated rod warmer is the gold standard.

Common Applications for EXX18 Electrodes

You should reach for your low hydrogen rods whenever you are working with medium-to-high carbon steel. If you are welding something that is thicker than 1/4 inch, the cooling rate of the metal can be quite fast, which increases the chance of cracking.

Use these rods for:

  1. Structural framing: Building steel rafters or support columns for a workshop extension.
  2. Heavy vehicle repairs: Fixing cracked frames on trailers or agricultural equipment.
  3. High-stress joints: Any part that will experience constant load or cyclic stress.

Technique Tips for Success

Welding with low hydrogen rods feels a bit different than running a fast-freeze rod like E6010. You will find that the slag is heavier and the puddle is more fluid, which requires a steadier hand.

Keep your arc length tight. If you pull the electrode too far away from the metal, you risk introducing nitrogen and oxygen into the weld, which creates porosity. Maintain a consistent, short arc to let the shielding gas do its job.

Also, watch your travel speed. If you move too fast, you will trap slag in the puddle, creating inclusions that weaken the joint. Keep the tip of the rod pointed slightly toward the direction of travel to “push” the slag behind the puddle.

Frequently Asked Questions About Low Hydrogen Electrodes

Can I use low hydrogen rods on AC welding machines?

Some low hydrogen rods, like E7018-AC, are designed for both AC and DC, but many are DC-only. Always check the manufacturer’s label on the box to ensure your welder is compatible with the specific rod you have chosen.

Do I need to preheat my metal when using these rods?

For very thick steel or high-carbon alloys, preheating is often recommended even when using low hydrogen rods. It slows the cooling rate and further prevents the formation of brittle structures in the metal.

How do I know if my rods have absorbed too much moisture?

If you notice excessive porosity (tiny pinholes) in your weld beads, or if the arc is erratic and difficult to maintain, your rods have likely absorbed moisture. You can sometimes “recondition” them in a rod oven, but if they are badly compromised, it is safer to discard them.

Are E7018 rods the only low hydrogen type?

No, there are others like E7015 and E7016. However, E7018 is the most popular because the iron powder in the coating makes it easier to use and produces a smoother, more aesthetic bead for the average DIYer.

Final Thoughts on Mastering Your Welds

Choosing the right rod is the mark of a craftsman who respects the integrity of their work. By understanding which group of electrodes is low hydrogen type, you have already taken a major step toward safer and stronger fabrications.

Don’t be intimidated by the technical specs on the box. Start by practicing on scrap pieces of similar thickness to your project. Watch the puddle, keep your rods dry, and take your time to ensure your penetration is consistent.

Whether you are building a custom storage rack or repairing a piece of heavy equipment, using the right consumable gives you the peace of mind that your project will hold up for years to come. Grab some high-quality rods, fire up your machine, and keep practicing—your shop projects are only going to get better from here!

Jim Boslice
Latest posts by Jim Boslice (see all)

Similar Posts