Low Hydrogen Welding Rods Explained

Hydrogen is invisible, weighs almost nothing, and can crack a structural weld days after you finish it. That quiet threat is the whole reason a class of rods exists that welders guard like they are made of glass, keeping them sealed, heated, and dry. Understanding low hydrogen rods is really about understanding one enemy and how to keep it out of your welds.

Low hydrogen welding rods are stick electrodes with a special coating formulated to introduce very little hydrogen into the weld, which prevents hydrogen-induced cracking in strong and thick steel. The best known is 7018. Their defining trait, and their defining weakness, is that the coating absorbs moisture from the air, so keeping them dry is not optional. Here is what makes them different and how to handle them.

What makes a rod low hydrogen

Ordinary rods like 6010 and 6011 have cellulose coatings that actually generate hydrogen as part of how they work, which is fine for their jobs. Low hydrogen rods instead use a coating (typically containing calcium compounds and iron powder, and kept low in moisture) engineered to keep hydrogen out of the arc and the weld pool. Less hydrogen in the molten metal means far less risk of it becoming trapped and causing cracks as the weld cools and hardens.

That is the entire point of the category: strong, tough, crack-resistant weld metal for applications where a hidden crack would be dangerous, like structural steel, pressure vessels, and heavy equipment.

Why hydrogen causes cracking

When hydrogen dissolves into hot weld metal and then gets trapped as the weld solidifies and cools, it can lead to cracking, sometimes called hydrogen-induced or cold cracking. The insidious part is timing: this cracking can appear hours or even days after welding, in the weld or the heat-affected zone beside it. It is most dangerous in higher-strength and thicker steels, which cool faster and are more sensitive. Low hydrogen rods attack the problem at the source by minimizing how much hydrogen ever enters the weld.

Why low hydrogen rods must stay dry

Here is the catch that defines how you handle these rods. The low hydrogen coating is hygroscopic, meaning it pulls moisture from the air, and moisture is a source of hydrogen. A low hydrogen rod that has absorbed too much moisture stops being low hydrogen: it can carry that moisture into the weld as hydrogen and cause the exact cracking it was designed to prevent.

That is why the rules exist:

• Store them sealed and dry. Keep rods in their sealed packaging until use, and once opened, in a dry, warm rod oven for serious work.
• Do not use rods that have sat out in humidity for critical welds. Exposed low hydrogen rods can pick up too much moisture in hours.
• Rebaking to a manufacturer-specified temperature can restore rods that have absorbed moisture, which is why shops run rod ovens.
• Look for the MR designation. Some rods, like 7018 MR, have moisture-resistant coatings that tolerate exposure longer, a real advantage if you cannot run an oven.

Can you use a wet 7018 rod?

For any weld that matters, no. A 7018 rod that has taken on moisture defeats its own purpose and can put hydrogen into the weld, risking cracking. For a non-critical hobby tack you may not notice a problem, but the honest guidance is not to gamble on a damp low hydrogen rod for structural or high-stress work. Either use dry, properly stored rods, rebake per the maker’s spec, or reach for MR rods if your storage is imperfect.

Which low hydrogen rods to buy

The most common low hydrogen rod is 7018, and it is worth buying with storage in mind.

• Forney E7018 AC low-hydrogen electrodes are a dependable everyday low hydrogen rod for structural-strength welds on clean steel, running on AC-capable machines. The limitation is the whole point of this article: keep them dry, because their low-hydrogen benefit depends on it.
• Lincoln Excalibur 7018 MR electrodes are the choice when storage is not ideal, thanks to the moisture-resistant (MR) coating that tolerates exposure longer, plus premium arc characteristics. If you weld intermittently and do not own a rod oven, that MR formulation is genuine insurance.

How to decide: for a working shop with a rod oven, the standard Forney 7018 is a fine everyday rod. For a home welder without controlled storage, the MR version protects you from the moisture problem that undermines ordinary low hydrogen rods.

The bottom line

Low hydrogen rods exist to keep hydrogen, and the cracking it causes, out of strong, thick, critical welds. Their coating delivers that benefit only while it stays dry, so storage is inseparable from performance: seal them, keep them warm and dry, rebake per spec, or buy MR rods if your storage is imperfect. Handle them right and 7018 and its relatives give you some of the strongest, most reliable welds you can lay with a stick machine.

FAQ

What makes a rod low hydrogen? A specially formulated coating (kept low in moisture, typically with calcium compounds and iron powder) that introduces very little hydrogen into the weld, unlike cellulose-coated rods such as 6010 that generate hydrogen. The most common example is 7018.

Why do low hydrogen rods need to stay dry? Their coating absorbs moisture from the air, and moisture is a hydrogen source. A rod that has taken on moisture can carry hydrogen into the weld and cause the cracking it was meant to prevent.

Can you use a wet 7018 rod? Not for welds that matter. Moisture defeats the low hydrogen benefit and risks hydrogen cracking. Use dry, properly stored rods, rebake to the maker’s spec, or use moisture-resistant MR rods.

What does MR mean on a 7018 rod? Moisture resistant. The coating tolerates air exposure longer than standard 7018, which helps welders who cannot store rods in a heated oven.

What is hydrogen-induced cracking? Cracking caused by hydrogen trapped in the weld or heat-affected zone as it cools and hardens. It can appear hours or days after welding and is most dangerous in high-strength and thick steels.

Do I need a rod oven for 7018? For structural or critical work, yes, a rod oven keeps rods dry and lets you rebake them. For occasional hobby use, sealed dry storage or MR rods can be enough, but exposed rods lose their low hydrogen benefit.

References

• Lincoln Electric, low hydrogen electrode storage, rebaking, and Excalibur 7018 MR documentation (manufacturer), lincolnelectric.com.
• Hobart Brothers, E7018 and low hydrogen electrode handling guidance (manufacturer), hobartbrothers.com.
• American Welding Society guidance on hydrogen-induced (cold) cracking and low hydrogen electrode practice, aws.org.