Walk into most structural fab shops and the electrode rack holds E7018. It is the default SMAW choice for carbon and low-alloy structural steel — widely available, forgiving on fit-up, familiar to every journeyman welder who has spent time in a structural shop. E7016 appears less often in North American structural fab, but it shows up in contractor submittals, overseas fabricator packages, and shops with older AC-only welding equipment. CWIs reviewing those submittals need to know what changes and what does not.

The two electrodes share the same classification baseline. Both are AWS A5.1 low-hydrogen SMAW electrodes, both produce 70 ksi minimum tensile weld metal, and both qualify as F-number 4 filler metal under AWS D1.1. The differences are in coating chemistry, power source flexibility, and deposition rate — not in the metallurgical class of the deposit.

The AWS A5.1 Classification System

AWS A5.1 encodes four properties in the electrode classification string. For E7018:

  • E = electrode
  • 70 = minimum tensile strength of weld metal in ksi (70,000 psi minimum)
  • 1 = all-position: flat, horizontal, vertical up, and overhead
  • 8 = coating type: iron-powder, low-hydrogen, designed for DCEP (and some AC formulations)

The suffix digit is where E7016 and E7018 diverge. Suffix 6 designates a low-hydrogen coating with a potassium-stabilized flux that supports both AC and DCEP power. Suffix 8 designates a low-hydrogen coating with iron powder added to boost deposition rate, optimized for DCEP.

Both suffix types produce low-hydrogen weld deposits within the same base class. The "low-hydrogen" designation means diffusible hydrogen is controlled at the manufacturing level through coating chemistry — not by baking or drying the electrode before use (though proper storage still matters; more on that below).

E7018: The Structural Shop Standard

E7018 dominates North American structural fabrication for a reason. The iron powder in the coating increases deposition rate by 20–30% compared to E7016 at the same diameter and current setting — meaningful throughput on long fill passes in heavy groove welds or on high-volume fillet welding. The slag is dense and self-releasing on most passes, and the arc is stable and easy to control at the current ranges used in structural work.

The limitation is polarity: E7018 is designed for DCEP (reverse polarity). Running an DCEP-formulated E7018 on an AC transformer produces an unstable, spitting arc and poor slag coverage. Some manufacturers offer E7018-AC formulations specifically for AC machines, but standard E7018 from a structural electrode brand should be run on DC.

For WPS documentation, the polarity requirement matters. Polarity is an essential variable under AWS D1.1:2025 Table 6.6 — changing from DCEP to AC on a WPS written for E7018 is a procedure change, not a minor adjustment. A detailed SMAW WPS for E7018 on structural steel specifies the electrode classification, diameter range, polarity, and current range as minimum content.

E7016: The AC-Compatible Alternative

E7016's distinguishing characteristic is its potassium-bearing coating, which stabilizes the arc under AC current. Potassium has a low ionization potential compared to sodium, making it easier to maintain arc continuity through the current zero-crossing that occurs 100–120 times per second on a 50–60 Hz AC transformer machine.

This matters in two practical situations:

Shops with AC-only welding equipment. Older transformer-based SMAW machines are common in smaller shops, rental fleets, and international markets. If the equipment cannot produce DC output, E7016 provides low-hydrogen compliance without capital investment in new welding machines.

Remote field welding on generator power. Engine-driven generators sometimes produce DC output of inconsistent quality depending on load, speed, and age. E7016 tolerates AC operation as a fallback without the arc instability that E7018 would show on a rough-output generator.

The trade-off is deposition rate. Without iron powder in the coating, E7016 deposits slightly less filler metal per unit time than E7018 at equivalent diameter and current. For high-volume structural fab, the difference is noticeable on production throughput. For occasional repairs, site welding, or lower-volume work, the difference is negligible.

Hydrogen Designation: H4, H8, H16

The base classification — E7016 or E7018 without an optional suffix — is tested to ≤16 mL/100g diffusible hydrogen, equivalent to the H16 designation. Both electrodes are also available with supplemental hydrogen test designations:

  • H4: ≤4 mL/100g — the tightest designation, used for high-carbon-equivalent base metals, heavy restraint, or cold service applications
  • H8: ≤8 mL/100g — common for general structural work involving A572 Gr. 50 or thicker sections
  • H16: ≤16 mL/100g — base level; adequate for A36 and low-restraint applications

The designation is independent of the coating type. E7016-H4 and E7018-H4 are equally controlled for hydrogen; the difference remains in deposition rate and AC capability, not in hydrogen performance. When a specification or WPS requires a specific H designation — as is common on A913, A514, or demand-critical welds — both electrode types can meet it. Specify the designation by name: "E7018-H4" or "E7016-H4" rather than just "low-hydrogen."

For a full explanation of conditioning, storage, and the consequences of H-designation violations, see low-hydrogen electrode conditioning and hydrogen designations.

Storage Requirements: No Difference

No distinction applies between E7016 and E7018 here. Both are low-hydrogen electrodes and both require the same handling protocol per AWS D1.1:2025 and electrode manufacturer guidance:

  • Unopened containers: store in dry conditions below 50% relative humidity at ambient temperature
  • Opened containers: transfer immediately to a rod oven at 250–300°F (121–149°C)
  • Time-out-of-oven: limited per the electrode manufacturer's published data sheet (typically 4 hours maximum in ambient humidity conditions below 90°F [32°C])
  • Reconditioning: electrodes that exceed the time-out-of-oven limit can be reconditioned once at 700–800°F (371–427°C); a second reconditioning is the maximum; beyond that, discard
  • Welder-carried electrodes: in a quiver or heated portable rod oven during the shift

A CWI performing a pre-weld inspection checks rod oven temperature and electrode handling as a standard inspection point. An E7016 rod sitting on a workbench in a humid shop is just as compromised as an E7018 in the same condition.

WPS and Essential Variable Implications

If your shop is evaluating a WPS submittal that specifies E7016, or considering whether to add E7016 as an alternative on an existing E7018 procedure, verify these points:

F-number compatibility. E7016 and E7018 are both F-number 4 under AWS D1.1's filler metal grouping system. A prequalified WPS covering F4 low-hydrogen electrodes for SMAW can accommodate either, subject to the WPS's stated classification.

Classification as written on the WPS. If the WPS lists "AWS A5.1 E7018" specifically, substituting E7016 changes the A5.1 classification suffix. This is an essential variable change under AWS D1.1:2025 Table 6.6 and requires a WPS revision or a separate procedure. A WPS written to allow "F4 low-hydrogen SMAW electrodes meeting AWS A5.1" is broader and may cover both without revision.

Polarity listing. E7016 runs on DCEP or AC; E7018 on DCEP (and some AC formulations). If the WPS specifies DCEP only and you are switching to E7016 on AC, polarity is an essential variable — a procedure revision is required. If adding E7016 as an alternative for AC operation on a job site, the WPS should list DCEP or AC as the current type.

Diameter range. No difference between E7016 and E7018 diameter classification. Both are available in standard structural diameters (3/32, 1/8, 5/32, 3/16, 7/32 in). The WPS diameter range applies equally to both.

Choosing the Right Electrode for Your Shop

For most North American structural fab shops with DC welding equipment and volume production, E7018 is the correct default. The higher deposition rate and dominant position in the supply chain (availability, cost, consistency across manufacturers) make it the practical standard.

E7016 makes sense when:

  • The power source is AC-only or produces unreliable DC output
  • The project is international and the fabricator's standard consumable supply uses E7016
  • The WPS requirement specifies AC capability explicitly
  • A temporary field repair situation limits access to DC equipment

The metallurgical result — weld chemistry, mechanical properties, and hydrogen control — is equivalent between the two when operated within their respective qualified parameter ranges. Neither electrode is inherently superior to the other for structural steel quality; the choice is an equipment and logistics decision, not a quality decision.

For AWS D1.1-compliant WPS documentation that covers SMAW procedures for both E7016 and E7018 applications with the required essential variable detail, structured software reduces the risk of missing a classification or polarity notation that becomes an audit finding.