What Are Welding Rods Made Of? Core Wire, Flux & Alloy Guide

A hobbyist pulls a sticky rod out of a damp garage box, strikes an arc, and gets porosity and a crumbling bead instead of a clean weld — so is the rod defective, or is what it’s made of simply not what he assumed? Welding rods are far more engineered than a coated metal stick: the wire core, the flux chemistry, and even the moisture in that coating decide whether your weld holds a bridge together or falls apart.

Write section 1, 560-840 words, target 700. Include hook briefly, answer immediately, anatomy, SMAW vs bare vs flux-cored, AWS A5.1 fact, OSHA fume fact, internal links (a couple naturally), external links inline.

Need to weave internal links once each — but I only have one section; pick natural ones: “All Position Welding Rod Guide” maybe, “Advantages of Stick Welding”, “Aluminum MIG Welding”. External: Miller Welds for AWS A5.1, OSHA for fume constituents, Lincoln Electric for AWS classifications maybe.

Keep within 700 words. Let’s draft.

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What Are Welding Rods Made Of? The Short Answer

Picture the scene: a hobbyist digs a half-forgotten box of rods out of a damp garage, strikes an arc, and watches the bead crumble into porosity instead of laying down clean metal. The rod looked fine. So what went wrong?

Here is the short answer. A welding rod is not a simple metal stick. It is a small, carefully engineered consumable, and most of what you need to know fits into two parts:

• The core wire — the solid metal center that melts and becomes the filler metal in your joint.
• The flux coating — the mineral and chemical jacket that burns in the arc to create shielding gas, form slag, stabilize the arc, and feed alloying elements into the weld pool.

In a stick electrode, also called a SMAW (shielded metal arc welding) electrode, both parts matter. The core wire supplies the deposit; the coating controls the atmosphere around it. When someone asks what welding rods are made of, the honest answer is: a specific alloy plus a specific chemistry, matched to a specific job.

Two Parts, Two Jobs

The core wire is drawn to a standard diameter and a tightly controlled chemistry. On common mild steel electrodes it is low-carbon steel with small additions of deoxidizers like manganese and silicon, which keep oxygen from forming porosity in the pool. The coating is a blend of powdered minerals, cellulose or rutile, carbonates, fluorides, ferroalloys, iron powder, and a binder such as sodium silicate that holds it onto the wire.

When the arc strikes, that coating does several things at once. It gas-shields the molten metal from the air, it forms a slag blanket that slows cooling and protects the bead, and it can add alloys or control hydrogen. The wire alone would weld, but it would weld badly. The coating is why a stick rod works outdoors in a breeze where a bare wire process would fail.

Stick Electrodes, Bare Rods, and Flux-Cored Wire

Not every filler is built this way, and knowing the difference clears up most beginner confusion.

Family	What it’s made of	How the arc is protected
SMAW stick electrode	Metal core wire + flux coating	Gases and slag from the burning coating
TIG (GTAW) filler rod	Bare solid alloy, no coating	External inert shielding gas, usually argon
MIG (GMAW) wire	Bare solid wire on a spool	External shielding gas, or flux inside the wire
Flux-cored wire	Steel sheath packed with powdered flux or metal powder	Flux-derived gas, sometimes plus external gas

Bare rods used in TIG and MIG contain no flux coating whatsoever. Their protection comes from a bottle, not the rod. Flux-cored wire flips the stick electrode inside out, putting the flux powder in the middle of a hollow tube. If you want to see how that logic plays out with aluminium, our guide to aluminum flux welding walks through where it works and where it does not.

Why the Chemistry Is Written in Code

Because composition drives performance, the industry classifies electrodes by number rather than by description. In North America, AWS A5.1 is the specification covering carbon steel stick electrodes, including the familiar E6010, E6011, E6012, E6013, E7014, E7024, and E7018. Other specifications cover stainless, aluminium, and low-alloy fillers. Each number encodes strength, position, coating type, and current.

That is also why “what is this rod made of” has real safety weight. Welding fume is literally built from volatilized coating, wire, and base metal. OSHA lists iron, manganese, titanium dioxide, calcium, and silicates among the common constituents, and some rods add chromium, nickel, or fluorides to that list.

The rest of this guide takes each layer apart: the wire, the coating, the code, the alloy families, and what all of it means at the bench. If you are still deciding whether stick is worth learning at all, the case for it is laid out in advantages of stick welding.

The Core Wire: The Metal Inside the Rod

Peel back the flux coating of a stick electrode and you find a plain-looking metal rod. That core wire is the backbone of the weld: it carries the current, melts into the joint, and becomes the deposited weld metal. The coating gets the attention, but the wire holds the structure together.

Most Stick Rods Start as Low-Carbon Mild Steel

For the common E60xx and E70xx stick electrodes that cover most shop and repair work, the core wire is low-carbon mild steel. In plain terms, it is mostly iron with a small amount of carbon and manganese, plus trace elements that are either left in from the steelmaking process or added on purpose.

Those deliberate additions matter more than they sound. Carbon-steel core wires carry small, controlled amounts of manganese, silicon, phosphorus, and sulfur:

• Manganese strengthens the steel and helps remove oxygen from the molten puddle.
• Silicon acts as a deoxidizer, helping the puddle stay quiet and sound.
• Phosphorus and sulfur are limited tightly because they embrittle weld metal.

Chemistry like this is not accidental. Manufacturers tune the core wire so the finished weld deposit meets the mechanical properties promised by the electrode’s AWS classification. As Lincoln Electric’s AWS classification guide explains, the numbers stamped on a rod are really a chemistry and performance specification, and the core wire carries much of that load.

Standard Diameters and How Much Metal the Wire Contributes

Stick core wire comes in standardized diameters so welders can match rod size to material thickness and amperage range. Under the AWS A5.1 specification, common sizes run from about 1/16 in (1.6 mm) up through 3/32 in, 1/8 in, 5/32 in (4.0 mm) and larger, with each diameter paired to a recommended current range and plate thickness.

Here is a point many beginners miss: for a plain-extruded coating, the core wire alone typically contributes most of the deposited weld metal, because the flux burns off as gas and slag and leaves very little metal behind. But many rods are “iron powder” types. Iron powder blended into the coating fuses into the puddle alongside the melting core wire, and deposition rate climbs sharply. The AWS A5.1 annex notes on electrodes like E7018 and E7024 reflect exactly this: iron-powder coatings can add substantial weld metal on top of what the core wire provides, which is why those rods run faster and fill joints quicker than their plain counterparts.

Where Tensile Strength Actually Comes From

Remember the “70” in E7018: it means the deposited weld metal must meet a minimum tensile strength of 70,000 psi. That strength is engineered into the finished weld through a combination of the core wire chemistry, the alloying elements the flux adds during the arc, and the cooling behavior of the puddle. The wire sets the baseline; the flux fine-tunes it. The same logic applies to E8018-B1 or other alloy-rod designations, where chromium and molybdenum additions in the wire and flux produce heat-resistant properties, a topic we look at further in our guide to alloy steel welding electrodes.

The Same Idea, Different Names: ER-Numbered MIG Wire

Bare filler wire used in MIG welding follows the same philosophy with a different label system. A spool marked ER70S-6 tells you a lot:

• E or R (shown together as ER) means the product works as either an electrode or a filler rod.
• 70 again means 70,000 psi minimum tensile strength.
• S means it is a solid wire (an F would mean flux-cored).
• 6 is the chemical subclass. The “-6” wire carries extra silicon and aluminum deoxidizers, which also help the arc burn through the light mill scale left on the wire surface itself.

That last detail surprises people: the deoxidizers in ER70S-6 do double duty, cleaning the wire as well as the puddle. It makes S-6 a forgiving, general-purpose choice for mill-scaled hot-rolled steel, while a cleaner S-1 or S-2 wire suits applications where smoother feeding and less silicon residue matter, such as thin automotive sheet or out-of-position work. If you are welding aluminum instead, the whole material palette changes to silicon-aluminum and magnesium-aluminum alloys such as 4043 and 5356, which we cover in depth in the aluminum MIG welding guide and the companion piece on prepping aluminum before welding.

Why the Core Wire Quality Shows Up in the Bead

Wire is drawn from steel rod stock through a series of dies to its final diameter, and consistency in that drawing shows up at the arc. A wire with tightly controlled diameter, clean surface condition, and uniform chemistry feeds smoothly and arcs steadily. Skimp on the wire and you get erratic feeding, unstable arcs, and weld metal that never quite reaches the strength the classification promised. That is why reputable manufacturers publish chemistry certificates: the core wire is not a commodity stick with a coating slapped on it. It is a precision alloy, engineered from the center out.

The Flux Coating: What the Outer Layer Is Made Of

If you stripped the coating off a stick electrode, you would be left with a fairly ordinary low-carbon wire that would burn erratically, spatter badly and leave a porous, slag-covered mess. The coating is where the engineering lives. It is not paint or glue, but a carefully balanced mineral recipe that melts, decomposes and reacts in the arc to do six jobs at once:

• Stabilize the arc so it does not wander or stutter.
• Produce shielding gas that keeps oxygen and nitrogen out of the puddle.
• Form a protective slag that floats on the weld pool and cools slowly over it.
• Deoxidize the puddle, scavenging oxygen before it can form blowholes.
• Add alloys to tune tensile strength, toughness and bead shape.
• Control hydrogen, the main culprit behind cold cracking in restrained joints.

Six jobs, one thin layer of powder and clay pressed onto a wire. The trick is that different ingredients deliver different jobs, and the ratio between them is exactly what separates one AWS classification from another.

Ingredient Families and What Each One Does

Coating chemistries generally fall into a handful of families. Most electrodes use a blend rather than a single material:

Ingredient	Family / Role	What it does in the arc
Rutile (titanium dioxide)	Arc stabilizer, slag former	Gives a soft, smooth arc and a fast-freezing slag that is easy to control; the basis of E6013-style titania coatings.
Cellulose (wood pulp fibre)	Gas producer	Breaks down into a hydrogen-rich gas stream that blasts the puddle, producing deep, forceful penetration.
Calcium carbonate + calcium fluoride (lime-fluoride)	Basic / low-hydrogen slag	Creates a basic slag that deoxidizes and desulfurizes the weld while keeping diffusible hydrogen low.
Feldspar and kaolin (clay minerals)	Binders and arc stabilizers	Give the coating its plasticity so it can be extruded onto the wire, and help stabilize the arc in titania rods.
Graphite	Gas former, arc aid	Adds carbon and generates gas for shielding; helps arc initiation.
Ferromanganese, ferrosilicon	Ferroalloys	Deoxidize the puddle and add manganese and silicon back into the deposit for strength.
Iron powder	Deposit builder	Is itself consumed as weld metal, boosting deposition rate and letting a 7018 bead fill a joint in fewer passes.
Sodium silicate, resins	Binders	Hold the whole mineral mix to the wire through handling and arc strike.

What an SDS Actually Lists for Common Rods

Manufacturers publish Safety Data Sheets that name the ingredients rather plainly. A typical SDS covering E6010, E6011, E6013, E7014 and E7018 electrodes lists iron, titanium dioxide, kaolin, feldspar, cellulose and manganese, each with a percentage range covering both the coating and the core. Reading one side by side with the next makes the differences obvious:

• E6010 / E6011: roughly 5–10% cellulose in a sodium- or potassium-based coating. That cellulose decomposes into a hydrogen-rich gas stream, which is why these rods dig deep through root gaps and rusty plate, as explained in Miller’s guide to common electrodes.
• E6013: titanium dioxide dominates, with clay binders doing much of the rest. The result is a soft arc, shallow penetration, light spatter and a slag that lifts off in one piece.
• E7018: a calcium carbonate/calcium fluoride lime-fluoride coating with iron powder and ferroalloys, no cellulose. Because basic coatings pick up hydrogen readily, the rods are baked and sealed at the factory to hold diffusible hydrogen at or below the H4/H8 levels marked on the wrapper.

The Washington Pressbooks welding text walks through these coating families in the same functional terms, and the pattern holds across brands: rutile rods behave like rutile rods, basic rods behave like basic rods, no matter whose logo is on the box.

This is also why two rods with identical tensile strength can be completely different to weld. An all-position job that demands flat-position control may still point you toward a 6010 root pass and a 7018 fill, a pairing covered in our All Position Welding Rod Guide. And when the base metal carries alloy content rather than plain carbon, the ferroalloys in the coating start doing real metallurgical work instead of simple deoxidation, as discussed in Alloy Steel Welding Electrodes. The coating is not an accessory to the wire. For most stick welding, it is the part you are actually choosing.

Decoding the AWS Number: Composition Written in Code

Pick up any stick electrode box and you’ll see a code stamped onto the wrapper: E6013, E7018, or E6010. This isn’t a catalog number, but a compact recipe card. It tells you the minimum strength of the deposited weld metal, which positions it’s approved for, its required current, and most of all, what its flux is made of. These classifications come from the American Welding Society through documents such as AWS A5.1 for carbon steel stick electrodes, a standard maintained by the AWS A5 Committee on Filler Metals and Allied Materials.

The Four Digits, One by One

Using E7018 as an example, each digit has a purpose:

• E – Stands for “arc electrode”. Bare filler wires for TIG or MIG use an “R” or “ER” prefix instead, such as ER70S-6.
• 70 – The minimum tensile strength of the deposited weld metal in thousands of pounds per square inch. E70xx rods are rated for 70,000 psi, while E60xx rods are rated for 60,000 psi.
• 1 – The welding position. A “1” allows all positions, including overhead, while a “2” is limited to flat and horizontal fillet work.
• 8 – The coating type and current digit. This is the key to reading the flux chemistry. As outlined by Lincoln Electric’s guide to AWS classifications, this last digit is where the majority of a rod’s characteristics originate.

The Last Digit: A Direct Link to Flux

According to the OpenWelding Pressbooks electrode classification chapter, each coating digit corresponds to a specific covering and current requirement:

• x0 and x1 (cellulose sodium/potassium): Forceful, deep-penetrating arcs. E6010 runs on DCEP only, while E6011 runs on AC or DCEP.
• x2 and x3 (high titania sodium/potassium): Rutile based coatings. These provide a softer arc, lighter penetration, and easier starting, making E6012 and E6013 very forgiving.
• x4 (iron powder titania): Rutile with added iron powder to increase the deposition rate. E7014 is the most recognizable example.
• x5, x6, and x7 (low-hydrogen): Coatings based around calcium carbonate and calcium fluoride. These are designed to minimize hydrogen in the weld pool.
• x8 (low-hydrogen potassium with iron powder): The family of E7018. The iron powder boosts deposition while maintaining the low-hydrogen benefits of a lime-fluoride covering.

Common Electrodes at a Glance

Electrode	Coating Type	Flux/Core Traits	Typical Use
E6010	High cellulose sodium	Cellulose + sodium, DCEP	Pipe root passes, dirty or rusty steel
E6011	High cellulose potassium	Cellulose + potassium, AC/DCEP	Field repairs, AC-only machines
E6012	High titania sodium	TiO₂ + sodium	Fast-fill on mild steel, flat and horizontal
E6013	High titania potassium	TiO₂ + potassium	Thin sheet, beginners, general repairs
E7014	Iron powder titania	Rutile + iron powder	Increased deposition with easy cleanup
E7024	Iron powder high titania	Heavy iron powder load	High-deposition flat and horizontal production work
E7018	Low-hydrogen potassium, iron powder	CaCO₃/CaF₂ + iron powder	Structural steel, code work, all positions

For a more practical breakdown between these options, our all position welding rod guide covers field selection with more context.

Suffixes: H4, H8, and -1

Some rods go beyond the four-digit code. Suffixes such as H4, H8, and H10 denote the maximum diffusible hydrogen in the deposited weld metal, measured in milliliters per 100 grams of deposit. Lower values, such as H4, greatly reduce the risk of hydrogen-induced cracking on thick, restrained, or high-strength joints, which is why they are often required for structural work.

Additionally, the -1 designator (such as E7018-1) indicates supplemental requirements, most notably improved low-temperature impact toughness. This isn’t added strength, but notch toughness for cold service conditions. Both of these are covered in detail by Lincoln Electric’s classification reference and Miller’s common electrode Q&A.

It’s worth remembering that the classification only applies to the deposited weld metal. The core wire is typically a plain low-carbon steel, and it’s the flux that provides the alloying elements to reach those properties. For alloys outside of mild steel, entirely different specifications apply, which are explored in our alloy steel welding electrodes guide.

In short, read the last digit before you strike the arc. With a little practice, the AWS code will tell you almost everything you need to know about what’s inside that rod.

Flux-Cored, Metal-Cored and Bare Rods: Other Ways to Build a Filler

Stick electrodes are only one branch of the filler metal family. Plenty of modern welding happens with wire on a spool or a bare rod fed into an arc, and those consumables follow the same two-part logic as a coated stick: a metal that becomes the weld, plus something added to control the arc, the atmosphere, or the chemistry. Once you can read what a tubular or bare filler is packed with, you can predict how it will behave before you strike an arc.

Self-Shielded Flux-Cored Wire (FCAW-S)

Flux-cored wire looks like solid MIG wire, but it is not. It is a low-carbon steel sheath rolled into a tube and filled with a powdered flux charge: mineral fluorspar (calcium fluoride) for arc action and fluid slag, slag formers such as titanium dioxide and silicates, ferroalloys like ferromanganese and ferrosilicon for deoxidation and alloying, arc stabilizers, and often iron powder to boost deposition. When the arc melts the wire, that charge breaks down into a shielding gas envelope and a protective slag layer, exactly like a stick coating does.

Because the wire shields itself, FCAW-S needs no external gas cylinder. That makes it the practical choice outdoors, in drafts, and on dirty or coated plate where a gas envelope would blow away. It runs all-position with practice, deposits metal fast, and penetrates deeply. The trade-offs are heavier slag, more fume, and a bead that needs cleaning before painting or inspection.

Gas-Shielded Flux-Cored and Metal-Cored Wire

Gas-shielded flux-cored wire (FCAW-G) still carries a mineral flux, but it leans on an external gas, usually CO₂ or an argon-CO₂ mix. With the gas doing part of the shielding work, the flux charge can be lighter, which means less smoke, a flatter and cleaner bead, lower spatter, and easier out-of-position welding. It is common in structural and shipyard work because it combines flux-cored deposition rates with a tidier weld surface.

Metal-cored wire is the cousin people often confuse with flux-cored. It is a tubular sheath filled with metal powder rather than mineral flux, so it produces almost no slag. The powder blend, which can include iron, ferroalloys, and alloying elements, gives higher deposition rates, smoother transfer, and lower spatter than solid wire, and it bridges gaps well on fit-up that is not perfect. It generally needs a shielding gas and works best flat and horizontal.

Wire type	Inside the sheath	Shielding	Best suited to
FCAW-S (self-shielded)	Mineral flux, ferroalloys, iron powder	None required	Outdoor, windy, dirty or thick plate
FCAW-G (gas-shielded)	Lighter flux charge	CO₂ or mixed gas	Structural work, all-position, cleaner beads
Metal-cored	Metal powder, alloy additions	Usually gas-shielded	High-speed deposition, wide joints, thin-to-thick bridging
Solid MIG wire	Nothing, solid alloy wire	Gas required	Clean fabrication, sheet metal, controlled shop work

Stainless versions of both tubular types are covered by AWS A5.22/A5.22M, the specification for stainless steel flux-cored and metal-cored welding electrodes and rods, where the designation itself tells you the weld metal chemistry, the welding positions allowed, and the shielding gas the wire needs.

Bare MIG, TIG and Laser Filler Rods

Bare fillers carry no flux at all. Protection comes entirely from the shielding gas, the tungsten arc, or, in laser processes, the beam envelope. That means the alloy has to be right on its own: there is no flux to fix a bad chemistry match or scavenge contaminants. Solid MIG wire such as ER70S-6 gets its deoxidizers, mainly silicon and manganese plus a touch of aluminum, right into the wire drawing process, and TIG rods are the same alloys cut into straight lengths.

Two standards cover most bare non-ferrous and stainless rods. AWS A5.9 classifies bare stainless electrodes and rods, and within that specification the chromium content of the filler metal is not less than 10.5%, the threshold that makes the deposit stainless rather than merely corrosion-resistant steel. The common grades are ER308L for 304 stainless and ER316L for molybdenum-bearing 316; the “L” simply means low carbon, which reduces carbide precipitation and keeps the weld zone from sensitizing during service.

AWS A5.10 covers bare aluminum filler rods such as ER4043 and ER5356, classified by chemical composition rather than strength. ER4043 is an aluminum-silicon alloy, roughly 5% silicon, that flows beautifully, resists cracking, and is the default for most aluminum except anodized parts, where it discolors. ER5356 is aluminum with about 5% magnesium: stronger, stiffer, more crack-sensitive on certain alloys, and preferred for 5000-series base metal, marine work such as aluminum boat welding, and anything that will see impact. If you are feeding these wires mechanically, our aluminum MIG welding guide walks through gas, cleaning, and wire feed settings, while aluminum flux core welding covers what does and does not work when an aluminum tubular wire is the only option on the job. For process work beyond wire, alpha laser welding shows how bare filler is introduced into a laser keyhole with far less heat input than an arc.

Whichever family you pick, the classification prefix is your first clue to composition: ER before the number means a rod suitable for both arc and gas welding, R means rod only, and E means electrode. Read the number after it, and you know the alloy before the box is ever opened.

Rod Materials by Metal: Stainless, Aluminum, Nickel, Cast Iron and Copper

Ask ten welders what a welding rod is made of and you will get ten answers, because the honest answer depends entirely on the metal you are joining. A filler rod is not a generic coated stick; it is a carefully balanced alloy chosen to behave like the base metal around it. Once you know the main alloy families and what gives each one its properties, rod selection stops being guesswork.

Mild Steel Fillers: The Everyday Workhorse

The rods most hobbyists buy first are low-carbon mild steel with small additions of manganese and silicon for deoxidation. That same chemistry runs through E6013 and E7018 stick electrodes and through ER70S-6 MIG wire. They are cheap, forgiving and strong enough for general fabrication. When the job involves quenched-and-tempered or high-strength low-alloy steel, you move into a different family where the core wire carries chromium, molybdenum or nickel additions, as covered in our alloy steel welding electrodes guide.

Stainless Steel Rods: Iron, Chromium and Nickel

Stainless fillers are iron-chromium-nickel alloys. Under the AWS A5.9 specification, stainless filler wires and rods must contain at least 10.5% chromium with iron as the balance, which is exactly the threshold that gives stainless its passive, rust-resistant oxide layer. The common grades break down like this:

• ER308L – roughly 19-20% chromium and about 10% nickel; the standard filler for 304 stainless.
• ER309L – higher chromium and nickel content for welding stainless to carbon steel, or for a first pass over cast iron.
• ER316L – adds 2-3% molybdenum for better pitting resistance in chemical and marine exposure.

The “L” simply means low carbon, which reduces carbide precipitation in the heat-affected zone so the weld stays corrosion resistant after welding.

Aluminum Rods: Silicon and Magnesium Alloys

Aluminum filler rods are not “pure aluminum.” ER4043 contains about 5% silicon, which makes the puddle more fluid and noticeably reduces crack sensitivity, making it the default for architectural and 6xxx-series alloys. ER5356 contains about 5% magnesium instead, giving higher strength and better corrosion resistance in water and marine service, though it is more sensitive to silicon-rich cracking. Prep matters as much as alloy here: a clean, oxide-free surface is half the weld, which is why proper aluminum cleaning before welding is non-negotiable. For practical process detail, see our aluminum MIG welding guide.

Nickel and Cast Iron Rods

Cast-iron repair rods are typically nickel, nickel-copper (the familiar “Ni-Rod”) or nickel-iron alloys. They are deliberately soft and machinable, because gray cast iron is hard, brittle and full of carbon that can poison a steel weld. Nickel resists carbon pick-up; nickel-copper gives a softer, easier-machining deposit for general patching; nickel-iron (such as ENiFe-CI) is stronger and better suited to heavy sections, ductile iron and repair welds that must be machined afterward.

Bronze, Brass and Brazing Rods

These copper alloys are the odd family out, because they usually melt below the base metal. Copper-zinc rods are brass, copper-tin rods are bronze, and silicon bronze (roughly 95% copper with silicon as the deoxidizer) is the favorite for brazing steel, cast iron, galvanized sheet and even some aluminum work. Since the base metal barely melts, dilution is minimal and distortion stays low.

Hardfacing and Tungsten-Carbide Rods

When wear resistance is the goal, the rod itself is a composite. AWS A5.21 classifies surfacing and hardfacing electrodes and rods, including tubular tungsten-carbide rods that are classified by the mesh range and quantity of tungsten carbide granules in the deposit. The core is a steel tube; the filler inside is crushed carbide that gets embedded in a tough matrix, used on bucket teeth, augers, crusher plates and plow shares.

The practical rule is simple: identify the base metal, decide what the joint must survive, then choose the alloy family that behaves like it. Getting that match right is what separates a repair that lasts from one that cracks within a week.

How Rod Composition Changes the Weld: E6010 vs E6013 vs E7018

Hand a welder three rods of the same diameter and identical 60,000 psi strength rating, and they will cut three completely different beads. That is the clearest proof that a welding rod is a chemical recipe, not just a coated stick. The core wire is largely the same low-carbon steel; what separates E6010, E6013 and E7018 is the flux, and the flux decides penetration, spatter, slag behavior, deposition rate and even which positions you can weld in.

E6010: Cellulose and Sodium for a Hard-Biting Arc

E6010 uses a high-cellulose sodium coating. Cellulose is an organic filler that burns almost instantly, producing a stream of gases plus a forceful arc action that blasts through mill scale, rust and surface contaminants. The result is an extremely tight, crisp arc with deep, narrow penetration and very fast-freezing slag, which is exactly why pipe welders trust it for root passes where full penetration matters more than pretty ripples. The same chemistry makes it comfortable out of position: the puddle sets quickly, so overhead and vertical-up work stays controllable. E6010 is a DC-only rod, while its AC-friendly sibling E6011 swaps sodium for potassium to keep the arc stable on alternating current, a handy option for farm repairs on rusty steel with an old buzz box.

E6013: Titania Flux for a Soft, Forgiving Arc

E6013 is built around rutile, meaning titanium dioxide. Titania softens the arc, lowers penetration and keeps spatter to a minimum, and the slag lifts off in easy sheets rather than chipping like armor. It runs well on AC or DC, needs very little arc cleanup, and is the rod most beginners strike their first arc with. The trade-off is honest: it prefers clean, relatively thin sheet metal and will not dig through heavy mill scale the way E6010 does. If you are welding thin material and learning puddle control, a rutile rod is forgiving. If you are welding dirty structural steel, its gentle arc is the wrong tool.

E7018: Low-Hydrogen Iron Powder for Strength and Toughness

E7018 flips the priorities. Its thick coating carries a high proportion of iron powder plus calcium carbonate and calcium fluoride (lime-fluoride), giving a smooth, quiet arc, medium penetration and a noticeably higher deposition rate than a bare-flux rod. The weld metal comes out strong and tough with good notch impact behavior, so it is the standard for structural and code work, and it performs acceptably in cold weather where a hard, fast-freezing bead might crack. The “18” coating is also low-hydrogen by design, which introduces a storage obligation: the coating absorbs moisture from humid air, and that hydrogen ends up in the weld. As Lincoln Electric’s AWS classification reference explains, the H4, H8 and H5 suffixes on the rod label state the maximum diffusible hydrogen in millilitres per 100 grams of deposited weld metal.

Production shops lean on a close relative, E7024, where the flux is loaded with even more iron powder. The heavier coating pushes deposition rates up substantially, but it works only flat and horizontal. That is the general pattern: the more iron powder in the flux, the higher the deposition, the more restricted the positions.

Rod	Coating chemistry	Penetration	Deposition	Slag	Positions	Current
E6010	High cellulose, sodium	Deep, narrow	Moderate	Fast-freezing, thin	All	DC only
E6011	High cellulose, potassium	Deep, narrow	Moderate	Fast-freezing, thin	All	AC/DC
E6013	Titania (rutile)	Shallow to moderate	Low to moderate	Easy-lifting	All	AC/DC
E7018	Lime-fluoride, low-hydrogen, iron powder	Medium	High	Thick, glassy, peel-off	All	AC/DC
E7024	High iron powder, titania	Medium	Very high	Heavy, easy	Flat, horizontal	AC/DC

One more habit worth breaking: a smooth, shiny bead does not mean a sound weld. Appearance tells you about arc stability and travel speed; chemistry tells you about tensile strength, toughness and crack resistance. A flawless-looking E6013 bead on a heavy, loaded joint is still a 60 ksi weld with shallow fusion, while a slightly rippled E7018 pass carries the impact properties a structure actually needs. Rod chemistry, not looks, determines performance, which is why stick welding remains dominant wherever the joint cannot be inspected by eye. For a deeper dive into how each classification maps to real-world behavior, Miller Welds’ electrode Q&A is a useful follow-up read.

What Welding Rods Are Made Of Means for Your Health

Everything you have read so far about core wire chemistry and flux ingredients has a second consequence that rarely gets discussed: the moment you strike an arc, some of that metal and mineral chemistry does not stay in the weld. It goes into the air you are breathing. A stick electrode is essentially a small chemical package designed to vaporize in a controlled way, and a portion of what burns leaves the weld pool as fume, smoke, and gases that drift straight through your breathing zone.

What Is Actually in Welding Fume

The fume is not one thing. OSHA’s fact sheet on controlling hazardous fume and gases during welding lists aluminum, arsenic, cadmium, chromium, manganese, nickel, vanadium, and zinc among the metals commonly found in welding fume. Where each one comes from depends directly on what the rod is made of:

• Core wire: iron oxide from the steel itself, plus manganese and silicon from the deoxidizer additions in E60xx and E70xx rods.
• Flux coating: titanium dioxide from rutile coatings (E6013, E7014), sodium and potassium compounds from arc stabilizers, and carbonates that release carbon dioxide as shielding gas.
• Fluorides: calcium fluoride in lime-fluoride and low-hydrogen coatings breaks down into airborne fluoride compounds. OSHA notes these fluoride compounds as a cause of metal fume fever, with symptoms like chills, fever, nausea, and a metallic taste that usually appear hours after exposure.
• Alloyed or stainless filler: welding stainless or alloy steel introduces chromium and nickel into the fume. Chromium in fume is largely hexavalent, Cr(VI), which is far more toxic than metallic chromium. If you are prepping or welding aluminum, the filler and cleaning residues add aluminum oxide to the mix, which is one reason careful Aluminum Cleaner for Welding: How to Prep Aluminum Right matters for both weld quality and air quality.

The Numbers Regulators Use

OSHA sets a permissible exposure limit, or PEL, of 5 mg/m³ for welding fume measured as total particulate in the welder’s breathing zone over an eight-hour shift. That is the general limit. Specific components have much stricter limits of their own:

Substance	OSHA PEL	Why it matters
Welding fume (total particulate)	5 mg/m³ as an 8-hour TWA	The baseline limit for overall fume load
Hexavalent chromium, Cr(VI)	5 µg/m³ as an 8-hour TWA under 29 CFR 1910.1026	One thousandth of the general fume limit; stainless and chrome-alloy rods are the source
Manganese	NIOSH recommends a far tighter REL than OSHA’s PEL	Prolonged manganese fume exposure can cause Parkinson’s-like symptoms, per OSHA

How Well Do Controls Actually Work?

Local exhaust ventilation, or LEV, is the first line of defense, and the data is encouraging. In NIOSH engineering-control evaluations of welding operations, total welding fume concentrations ranged from 2–60 mg/m³ without LEV and dropped to 3–13 mg/m³ with LEV in place. Good ventilation does not eliminate exposure, but it consistently pulls readings down and often below the PEL. The same evaluations emphasize that capture arms have to be positioned close to the arc, because fume rises and spreads within seconds.

Controls worth prioritizing, roughly in order of effectiveness:

1. LEV positioned at the source, within about a foot of the arc where possible.
2. Work position and airflow awareness: never weld directly upwind of your own face, and avoid working in a confined bay where fume pools.
3. Respiratory protection when engineering controls cannot get readings low enough, selected through a written program rather than guessed from a hardware-store cartridge.
4. Lower-fume consumables: low-manganese and low-alloy rods, and gas-shielded processes over covered electrodes where the job allows it. The tradeoff is real, since flux chemistry is what gives a rod its arc characteristics, so a lower-fume option may not match every application.

Understanding this tradeoff is part of reading any electrode guide properly, and the same thinking applies when you evaluate Alloy Steel Welding Electrodes: Selection, Use & Safety, because the more alloying elements in the core wire, the more of them end up in the fume.

The practical takeaway is simple: the ingredients that make a rod weld well are the same ingredients that become airborne. Knowing which coating family you are burning tells you which hazards to plan for, and that planning is what keeps a healthy welder healthy over a thirty-year career.

Storage, Handling and the Most Common Rod Mistakes

A welding rod is a chemical package with a shelf life. Crack a carton open in a humid shop and that package starts changing. Most welders lose good metal here, not because the rod was made wrong, but because it was stored, handled, or selected wrong. Every one of those failures traces back to the core wire or the coating.

Why Low-Hydrogen Rods Go Bad in the Box

Low-hydrogen electrodes such as E7018 get their name from their coating chemistry: calcium carbonate (limestone), calcium fluoride (fluorspar), ferroalloys, graphite, and a sodium silicate binder. That blend is deliberately alkaline, and the binder plus the powdered lime is hygroscopic. Left in open air, the coating adsorbs moisture, and when the arc breaks that moisture down, hydrogen splits off directly into the molten weld pool.

The amount of hydrogen that survives into the solidified weld is what the AWS H designators measure: H4, H5 and H8 tell you the maximum diffusible hydrogen in millilitres per 100 grams of deposited metal under standard test conditions. An E7018H4 rod deposits a measurably drier weld than a plain E7018 that has been sitting in a damp garage, even though the core wire is identical. Lincoln Electric’s overview of the AWS classification system walks through those suffixes in detail.

That hydrogen matters because of hydrogen-induced cracking, also called cold or delayed cracking. It does not happen while the puddle is fluid. It happens after the weld cools, usually in the heat-affected zone, and it needs three things together: diffusible hydrogen, a tensile stress (restraint, a thick joint, shrinkage), and a susceptible hard microstructure. Restrained, high-strength joints are the classic victims, and because the crack can appear hours after welding, it is the one that surprises people.

The defense is storage discipline:

• Use a rod oven. Low-hydrogen electrodes should be held at the temperature printed on the manufacturer’s data sheet, commonly around 250–300°F (120–150°C), and kept there until struck.
• Reseal opened packages. Leftover rods go back into the foil pouch with the desiccant, or into the oven. Do not leave them in the rod bin overnight.
• Re-bake per the data sheet only. Re-baking can restore dried-out rods, but temperature and time limits are strict. Overheating bakes out the binder and destroys the coating’s arc characteristics.
• Track exposure time. Manufacturers specify allowable open-air exposure and re-drying cycles. After that, the rod is scrap.
• Keep cartons off the floor. Concrete wicks moisture, and a paper carton left on a damp slab over a weekend will pull that moisture into the coating.

Cellulose-based rods like E6010 and E6011 are far more tolerant of damp, dirty field conditions. Their coatings already contain organic moisture by design, which is one reason they dominate repair and pipeline work while E7018 lives in a climate-controlled box.

Handling Rules That Protect the Coating

The coating is precisely engineered for arc behavior, so physical damage is chemical damage. Cracked, chipped, or loosely bonded flux causes arc wander, heavy spatter, and unmelted coating fragments trapped in the weld as inclusions. Bare spots on the wire let the electrode short-circuit against the workpiece at the wrong moment. Practical habits:

• Do not re-bend a rod that has already been heated near one end; the coating there is brittle.
• Do not drop or throw cartons, and do not drag rods through shop grime or puddle water.
• Inspect a rod before striking. If the flux is cracked along its length, throw it away. The cost of the rod is nothing next to the cost of cutting out a bad bead.

Four Mistakes That Have Nothing to Do With Moisture

1. Wrong rod for the base metal. Matching filler to base metal is a metallurgical requirement, not a suggestion. A mild-steel rod on alloy steel, or the wrong alloy steel welding electrode grade, gives you a weld whose strength and heat treatment don’t match the part, and dilution from the base metal can push the chemistry somewhere useless.
2. Dirty or corroded steel under a rutile rod. E6013 and other titania coatings have a soft arc that tolerates almost no contamination. Oil, mill scale, rust, or paint turns straight into porosity. Aluminum is less forgiving still, since the oxide layer and surface hydroxides must be removed with a dedicated process, as covered in aluminum cleaner prep for welding.
3. Ignoring polarity. Rods are formulated for a specific current. E6010 runs DC electrode-negative (straight polarity) for its deep, forceful arc; E7018 runs DC electrode-positive (reverse) for proper penetration and deposition, and AC-rated versions exist for job-site machines. Running a rod on the wrong polarity gives weak penetration, violent spatter, or an arc that will not stay lit.
4. Cold or damaged coating at the start. A rod that has absorbed surface dampness, or one used after freeze-thaw cycling in an unheated truck, will stutter and pop. The old “hold the rod against the plate to warm it” trick is a symptom of a rod that should have been stored properly in the first place.

None of this is exotic knowledge, but it separates a rod that performs to its classification from one that only looks like it. The composition is written into the designator; the performance is written into how you kept it.

How to Choose the Right Rod: A Practical Decision Guide

Here is the good news: you do not need a hundred electrodes on the rack. Outside specialized hardfacing and exotic alloy work, five stick electrodes cover the overwhelming majority of repair, fabrication, and structural jobs: E6010, E6011, E6013, E7018, and E7024. Picking between them is not about memorizing a catalog. It is about asking a short series of questions in the right order, because every answer narrows the field until one rod is obviously correct.

And once you understand what each rod is actually made of, selection stops being guesswork. A cellulose-sodium coating behaves nothing like a rutile coating, and a low-hydrogen iron-powder coating behaves nothing like either. Composition is the whole story.

A Seven-Step Selection Checklist

Work through these before you buy or strike an arc. Manufacturer guides such as Miller Welds’ common electrode reference follow the same logic.

1. Identify the base metal and its thickness. Most stick work is mild or low-carbon steel, which is why the E60xx and E70xx families dominate. Thickness drives diameter: thin sheet wants a small rod on low amperage, while heavy plate can take a larger diameter and a hot, deep-penetrating setting. Welding stainless, aluminum, nickel, or cast iron? Stop and switch alloy families entirely, because a mild steel rod is the wrong filler metal.
2. Check the required strength. The first two digits after the E give the minimum tensile strength of the deposited weld in thousands of psi: E60xx delivers 60,000 psi, E70xx delivers 70,000 psi. For light repair either is fine; structural work usually calls for 70,000 psi. This numbering comes from AWS A5.1, maintained by the AWS A5 Committee on Filler Metals and Allied Materials.
3. Consider the welding position. The third digit encodes it. A “1” means all-position, which matters the moment you leave the bench. An overhead or vertical joint rules out flat-only rods. Our all-position welding rod guide covers the positioning details.
4. Know your power source. A shop machine on DC open up the full range, including low-hydrogen E7018. Older transformer rigs, AC-only boxes, and engine-driven generators favor E6011, which runs happily on AC or DCEP. That is exactly why E6011 remains the go-to for farm and field repair.
5. Assess joint access and fit-up. An open root with a real gap wants a deep-penetrating rod like E6010. Poor fit-up and heavy bevels want fast fill, which is where an iron-powder rod such as E7024 earns its keep in flat and horizontal work.
6. Think about service conditions. Parts that see impact, low temperatures, vibration, or cyclic loading should be welded with low-hydrogen consumables for toughness. Corrosive or high-heat service pushes you toward stainless, nickel, or bronze filler instead of plain carbon steel. For alloyed steels, see our alloy steel electrode selection guide.
7. Confirm code requirements. Structural, pressure vessel, and pipeline work almost always names the exact classification and standard the inspector expects. Match it, and keep the certification paperwork.

Common Scenarios, Mapped to a Rod

Scenario	Go-to rod	Why it fits
Clean, new thin sheet; light fabrication	E6013 (or E6010 root)	Soft rutile arc, shallow penetration, low spatter
Pipe root pass or open-root joint	E6010	Deep, forceful penetration with fast-freezing slag
Outdoor or rusty repair on a generator rig	E6011	AC or DCEP operation; digs through mill scale and rust
Structural code work, heavy plate, load-bearing welds	E7018	Low-hydrogen, 70 ksi, strong and tough deposit
High-deposition flat and horizontal fill	E7024	Iron-powder coating lays metal fast with a smooth bead

Practical Tips Before You Buy

Buy a small pack of each of the five common rods and test them on scrap before committing to a bulk order. Keep opened E7018 in a sealed container or a rod oven, since that coating absorbs moisture and picks up hydrogen. Clean the base metal properly, set polarity to match the rod, and dial amperage to the diameter printed on the box. When the job is aluminum rather than steel, skip stick entirely and move to a dedicated process such as MIG with proper filler wire, starting with thorough surface preparation.

Learn the five rods, learn what they are made of, and you can walk into almost any repair situation, look at the metal in front of you, and pick the right electrode off the rack with confidence. For a broader look at why this process still holds up against newer alternatives, our guide to the advantages of stick welding makes the case, and the Lincoln Electric AWS classification reference is worth bookmarking for the next time an unfamiliar number shows up on the box.

Frequently Asked Questions

What are welding rods made of?

A stick welding rod has two parts: a metal core wire, usually low-carbon mild steel alloyed with manganese and silicon, and a flux coating made from minerals like rutile (titanium dioxide), cellulose, calcium carbonate, feldspar, kaolin, iron powder and binders. Bare TIG and MIG filler rods are just the alloy wire with no coating.

What is the coating on a welding rod called?

It is called the flux coating or covering. It melts during welding to produce shielding gas and slag that protect the molten puddle, while also stabilizing the arc and adding deoxidizers and alloys to the weld metal.

What does the number on a welding rod mean?

In the AWS system, E7018 breaks down as E = electrode, 70 = 70,000 psi minimum tensile strength, 1 = weldable in all positions, and 8 = low-hydrogen iron-powder coating type. The last digit effectively tells you the chemistry of the flux.

Are welding rods just steel?

Not always. Carbon-steel rods are mostly iron, but stainless rods contain at least 10.5% chromium plus nickel, aluminum rods are aluminum alloyed with silicon or magnesium, nickel rods are used for cast iron, and bronze brazing rods are copper-zinc or copper-tin alloys.

What are E7018 rods made of?

E7018 has a mild-steel core wire and a low-hydrogen calcium carbonate/calcium fluoride flux coating with added iron powder. The iron powder boosts deposition rate, and the low-hydrogen chemistry produces strong, crack-resistant welds for structural work.

Why does my welding rod make so much smoke?

The smoke is fume made from the burning flux coating and volatilized metals such as iron, manganese and titanium dioxide. Adequate ventilation or local exhaust is essential; OSHA notes prolonged manganese fume exposure can cause Parkinson’s-like symptoms.

Can you weld with a rusty or damp welding rod?

Surface rust on the core wire can be wiped off, but a damp low-hydrogen E7018 rod will introduce hydrogen and can cause porosity or cracking. Re-bake or replace wet electrodes according to the manufacturer’s data sheet rather than using them as-is.

What is the difference between flux-cored wire and a stick electrode?

A stick electrode is a solid wire with flux on the outside, while flux-cored wire is a hollow tube filled with powdered flux. Both shield the weld internally, but flux-cored wire feeds continuously and can deposit metal faster.

Do welding rod ingredients affect weld strength?

Yes. The core wire chemistry sets the minimum tensile strength class, and the flux adds alloying elements and deoxidizers while controlling hydrogen. An E7018 deposit is rated at 70,000 psi minimum versus 60,000 psi for E6013, purely because of that engineered chemistry.