Reading a Rod
A stick electrode is a steel core wire inside a flux coating whose burn shields the weld — and its AWS number states its strength, positions, and coating in a code you can read. · 10 min
Pick up a stick electrode and you are holding three tools in one. The steel core wire is filler metal, melting into the joint. The chalky flux coating around it burns in the arc and becomes two shields at once: a cloud of gas that pushes air away from the molten puddle, and slag — a crust of hardened flux — that blankets the cooling bead. The bare end is the electrical connection for the stinger. Every rod has this same construction; the recipe of the coating is what varies.
Guess before you learn
The number printed on the rod — E7018 — is mostly telling you what?
It is a standard AWS code, identical across every brand: tensile strength, positions, coating. If you guessed a catalog number, that is the natural read — most numbers printed on products are private codes. This one is public, and by the end of this folio you can read it off any rod on the shelf.
9–12
3–5
The coating is not paint. In the arc it burns into a gas cloud and a crust called slag, and both keep air away while the metal is melted. Air touching molten weld metal would fill the weld with holes.
The code E7018 reads in parts: 70 is the strength, 1 means it works in every position, 8 names the coating. Learn the parts and you can read any rod on the shelf.
6–8
Read E7018 left to right. E — an arc-welding electrode. 70 — minimum tensile strength of 70,000 pounds per square inch: pull a welded bar apart, and the weld metal itself resists at least that much stress. 1 — usable in all positions, flat through overhead. 8 — the coating and current family: low-hydrogen coating with iron powder, run on DCEP or AC.
The last digit matters as much as the first two. Coatings decide how the arc behaves — how hard it digs, how the puddle wets in, what dirt it tolerates — so two rods of equal strength can act like entirely different tools.
9–12
Tensile strength is stress at failure: 70,000 psi means a weld with one square inch of cross-section would carry 70,000 pounds before breaking. Matching filler to base metal is deliberate — common mild steel runs near 60,000 psi, so E70XX weld metal is slightly stronger than the plate, putting the weakest link outside the weld.
The 8 also flags chemistry: low-hydrogen. Hydrogen dissolved in hot weld metal migrates as the joint cools and can crack hardened zones hours after you finish. The coating is baked dry to keep hydrogen out — which is why a 7018 left in open air overnight is no longer the rod its number claims.
K–2
A welding stick is metal inside and a gray crust outside. When it burns, the crust makes smoke and a shell that keep air off the hot metal.
The numbers printed on the stick tell you what it is: how strong, and where it can work. Bigger first numbers mean stronger metal.
Undergrad
Coating families divide by slag chemistry. Cellulosic coatings (E6010, E6011) evolve gas violently — a forceful, deep-penetrating arc that tolerates contamination, at the cost of high diffusible hydrogen. Rutile coatings (E6013) run smooth and shallow. Basic low-hydrogen coatings (E7018) trade ease for cleanliness: calcium compounds, low moisture, a quiet arc, dense weld metal.
Hydrogen-assisted cracking needs three things at once: diffusible hydrogen, a susceptible microstructure, and tensile restraint. The electrode controls the first; preheat and heat input govern the second; joint design sets the third. Rod selection is one leg of a three-legged cracking analysis, not a preference.
Postgrad
AWS A5.1 defines the classification: strength designators are minimums measured on all-weld-metal specimens, and optional suffixes bound diffusible hydrogen (H8, H4 — milliliters per 100 g of deposited metal). Exposure limits and re-drying schedules — typically 260 to 430 °C for basic coatings — exist because reabsorbed moisture regenerates diffusible hydrogen within hours.
The coating also sets metal transfer. Cellulosic slags drive forceful, spray-like transfer with high arc pressure; basic slags favor larger droplets and a short workable arc. Deposition rate, slag detachability, and out-of-position control all trace back to slag viscosity and surface tension at the puddle rim.
slag
The hardened flux crust left on a finished bead. It protects the cooling metal, then chips off after the bead freezes.
Now the comparison that teaches rod choice. E6011 is a fast-freeze rod: its cellulosic coating burns with a forceful, digging arc that punches through rust, paint, and mill scale, and its puddle solidifies quickly — it will weld metal that should probably be cleaner. E7018 is the opposite: a smooth, quiet arc, dense strong weld metal, a handsome bead — but its low-hydrogen coating pulls moisture from the air, and a damp 7018 plants hydrogen in the weld. One tolerates dirt; the other demands care.
Why is this true?
Why a heated rod oven, rather than just a tightly sealed box?
A sealed can works only until it is opened. The oven holds rods warm enough that the coating cannot take moisture back from the air, so the door can open all day.
Decode a rod you have never met: E6013 — the steps fade as you master them
60 → 60,000 psi minimum tensile
1 → all positions
3 → rutile coating: a soft, easy-striking arc on AC or DC
Light fabrication on clean, thinner steel, where a gentle arc and easy slag matter more than maximum strength
A rod is a decision, not a part you grab blind. Read the code, weigh the metal's condition against the weld's duty, and store the rod the way its coating demands. Next folio you finally strike: the scratch start, the tap start, and the calm recovery for the rod that sticks.
Practice — new ink and old, interleaved
1.One sentence: why can a damp E7018 crack a weld hours after it cools?
2.In one sentence: why does lifting the rod far from the work kill the arc?
3.The last arc is out. What does the fire procedure still owe, and why?
A fire watch of at least 30 minutes, because a lodged spark can smolder unseen and flare after the work ends.
How close were you? Grade yourself honestly — it sets your review date.
4.Which statement about slag is true?
5.Order the parts of the E7018 code as you read them, left to right.
- 1 — all positions
- E — arc-welding electrode
- 8 — low-hydrogen coating
- 70 — 70,000 psi tensile
6.A machine holds 20 volts across the arc while pushing 120 amps. How many watts is the arc delivering?
7.A 1/8-inch E7018 (0.125 inch). Rule-of-thumb starting amperage?