Lincoln 7018-AC E7018 Low-Hydrogen Electrode — Overview
Lincoln 7018-AC is an AWS A5.1/A5.1M E7018 H8 low-hydrogen, iron-powder, basic-coated SMAW electrode specifically engineered to run reliably on AC welding machines — including low open-circuit-voltage (OCV) farm transformers and shop buzzboxes that cannot maintain stable arcs with standard DC-formulated E7018. The potassium-enhanced coating stabilizes the AC arc cycle without sacrificing the low-hydrogen (H8) diffusible hydrogen content and 70 ksi tensile strength that make E7018 the universal standard for structural and pressure vessel code welding. DC+ or AC; all positions. WeldingMart stocks Lincoln 7018-AC as an authorized Lincoln Electric distributor — select your diameter and package size in the variant selector above.
Specifications
| AWS classification | AWS A5.1/A5.1M E7018 H8 |
|---|---|
| Coating type | Low-hydrogen, iron-powder basic, potassium-enhanced for AC |
| Polarity | DC+ (DCEP) or AC |
| Welding positions | All positions: 1G, 2G, 3G, 4G (flat, horizontal, vertical, overhead) |
| Minimum tensile strength | 70,000 psi (483 MPa) |
| Minimum yield strength | 58,000 psi (400 MPa) |
| Elongation | 22% minimum |
| Charpy V-notch | 20 ft-lb at −20°F (27 J at −29°C) |
| Diffusible hydrogen | H8 — ≤ 8 mL/100g deposited weld metal |
| Typical current range | 3/32 in: 60–100 A | 1/8 in: 90–140 A | 5/32 in: 120–180 A | 3/16 in: 155–220 A | 7/32 in: 190–260 A |
| Available diameters | 3/32, 1/8, 5/32, 3/16, 7/32 in |
| Manufacturer | Lincoln Electric |
| Standards compliance | AWS A5.1/A5.1M; AWS D1.1 pre-qualified; ASME Section IX |
Applications & Industries
Lincoln 7018-AC brings the code-quality performance of E7018 to AC-only welding machines:
- Structural fabrication (AWS D1.1): Prequalified for use under AWS D1.1 on carbon steel structural shapes, plate, and pipe — the same code coverage as standard E7018 DC electrodes
- Farm and maintenance welding on AC machines: The most popular choice for welders whose Lincoln AC225, Idealarc, or similar AC transformer welder cannot run standard 7018 DC reliably
- Pressure vessel and pipe: ASME Section IX qualified procedures on carbon steel — fill and cap passes on pipe joints started with E6010 root pass
- Shipbuilding and general manufacturing: All-position filler and cap passes on carbon steel where low-hydrogen practice is required
- Multi-process environments: Shops with a mix of AC and DC machines that want one 7018 electrode that works across all machines
Process Technology — How to Run 7018-AC
- AC machine setup: Lincoln 7018-AC is formulated to run on AC machines with OCV as low as 50 V. Set current to the mid-range for the selected diameter. If the arc is unstable, increase amperage slightly — AC 7018 typically needs a slightly higher amperage setting than DC E7018 for comparable performance.
- Arc start: Scratch-start on AC. Start on scrap or use a run-on tab if available; the first inch of a cold-start bead will have a slightly elevated hydrogen level. The arc stabilizes within 1–2 seconds.
- Arc length: Short arc — 1× rod diameter maximum. A long arc increases spatter and diffusible hydrogen. This is more critical on AC because the arc extinguishes on each current reversal; short arc length helps re-ignition.
- Travel angle: 5–15° drag for flat and horizontal; 5–10° push for vertical-up with slight weave or pause-at-the-toes to avoid undercut.
- Slag removal: E7018 has a heavy, glassy basic slag that requires firm chipping. Remove completely between passes. Slag inclusions are the primary defect risk if interpass cleaning is skipped.
- Electrode drying after opening: See the Storage section below — 7018-AC requires oven storage after opening the container.
Storage & Handling — Low-Hydrogen Critical
Proper storage of E7018 is mandatory to maintain the H8 hydrogen designation and prevent hydrogen-induced cracking (HICC) in structural joints:
- Unopened packaging: Store in original sealed carton in a dry location at ambient temperature (40–120°F). Original Lincoln cartons are moisture-resistant but not hermetically sealed.
- After opening: Transfer immediately to a rod oven at 250–300°F (121–149°C). Do not leave 7018 in open air — moisture absorption begins within 30–60 minutes in humid conditions.
- In the field: Use a heated electrode quiver (at least 150–200°F). Remove only the rods needed for the current work session.
- 4-hour rule: Remove only what you need; use within 4 hours of removing from the holding oven. Any rods unused after 4 hours must return to the oven.
- Reconditioning: Per AWS A5.1, E7018 may be reconditioned at 500–800°F (260–427°C) for 1 hour. The Lincoln recommended temperature for 7018-AC is 500–600°F for 1 hour. Do not recondition more than once, and discard rods with visibly cracked or damaged coatings.
Frequently Asked Questions
- When should I use 7018 instead of 6013?
- Use E7018 for structural and code-governed welding on mild and low-alloy carbon steel — AWS D1.1 structural frames, ASME pressure piping, and any application requiring low-hydrogen weld metal. E6013 is for light fabrication, maintenance, and training where code compliance and low hydrogen are not required. On thick plate or restraining joints, E7018 significantly reduces the risk of hydrogen-induced cracking that would occur with E6013's higher hydrogen level.
- What is the difference between 7018 and 7018-AC?
- Standard E7018 is formulated primarily for DC+ operation, though most are technically classified for DC+ or AC. Lincoln 7018-AC specifically uses a potassium-enriched coating that provides exceptional arc stability on AC machines — including low-OCV farm welders that cannot maintain a stable arc with standard 7018. For DC machines (inverters, engine drives), standard Lincoln Excalibur 7018 is preferred. For AC machines, 7018-AC is the better choice.
- How do you store 7018 welding rods?
- After opening the original packaging, store 7018 rods in a rod oven at 250–300°F (121–149°C). In the field, use a heated quiver at 150–200°F. Remove only the rods needed for 4 hours of welding at a time. Rods exposed to ambient air for more than 4 hours should be returned to the oven or reconditioned at 500–600°F for 1 hour. Never store open 7018 without heat — moisture absorption will increase diffusible hydrogen above the H8 limit, risking weld cracking.
- Can 7018-AC run on DC machines too?
- Yes. Lincoln 7018-AC is dual-polarity — it runs on both AC and DC+ (DCEP). It is an excellent universal electrode for shops with a mix of AC and DC machines. Performance on DC is comparable to standard E7018, though Lincoln's Excalibur 7018 H4R (DC+ only, H4 hydrogen) is preferred for critical DC applications requiring the lowest possible hydrogen level.
- What is E7018 used for?
- E7018 is the most widely used structural SMAW electrode in North America. It is prequalified for AWS D1.1 structural steel welding and commonly used for fill and cap passes on carbon steel plate and pipe. It is the standard "production" electrode for fabrication shops, ironworkers, and pipe welders running multi-pass joints started with an E6010 root pass.
Browse all 7018 electrodes: Stick Welding Electrodes & Rods — or pair with a Lincoln Fleetweld 5P+ E6010 root pass for structural pipe procedure.