Lincoln 7018-AC RSP is a low-hydrogen E7018 welding rod specifically formulated for outstanding performance on AC (alternating current) power sources — including older transformer buzz-boxes, AC engine-driven welders, and multi-operator machines. Where standard E7018 electrodes can be finicky on AC due to re-ionization demands, the 7018-AC RSP's potassium-enhanced flux chemistry delivers smooth, stable arc performance even on 60 Hz AC machines with moderate open-circuit voltage. The RSP designation (Rotary Slag Peeling) indicates the flux is engineered for fast, self-releasing slag that peels cleanly in all positions for efficient production welding.
Lincoln 7018-AC RSP is Lincoln Electric's AC-optimized E7018 iron-powder low-hydrogen SMAW electrode. The AWS classification E7018 applies: "E" = electrode; "70" = 72,000 psi minimum tensile; "1" = all-position; "8" = low-hydrogen iron-powder covering with AC or DCEP polarity. The standard E7018 flux uses sodium-based stabilizers that can produce erratic arc behavior on 60 Hz AC power due to the brief extinction at each polarity reversal. Lincoln's 7018-AC RSP upgrades the stabilizer system with potassium compounds that re-ionize more easily at the AC zero crossing, producing a smooth, steady arc on AC machines that would cause standard E7018 to sputter, stick, or extinguish. This makes 7018-AC RSP the designated solution for contractors and shops that operate exclusively on AC power — construction sites with 480 V transformer-based welding machines, rural operations with AC engine-driven welders, and multi-operator welding systems that supply AC to each station. The RSP (Rotary Slag Peeling) technology ensures the slag lifts cleanly after each pass, maintaining production pace and inter-pass cleanliness consistent with standard low-hydrogen practice. Despite the AC optimization, 7018-AC RSP also performs well on DCEP for shops that transition between AC and DC machines.
| Property | Specification |
|---|---|
| AWS Classification | E7018 |
| Tensile Strength (min.) | 72,000 psi (496 MPa) |
| Yield Strength (min.) | 60,000 psi (414 MPa) |
| Elongation (min.) | 22% |
| Charpy CVN (−20°F) | 20 ft·lbf minimum |
| Flux Type | Low-hydrogen iron-powder, potassium-stabilized AC |
| Current | AC (optimized), DCEP |
| Positions | All (F, H, V-up, OH) |
| Special Feature | RSP — Rotary Slag Peeling for fast slag removal |
| Diameters | 3/32, 1/8, 5/32, 3/16 in |
The 22 % elongation and 20 ft·lbf CVN at −20 °F confirm that 7018-AC RSP meets the same structural performance requirements as standard E7018 — the AC optimization does not compromise the mechanical properties. This is important because some AC-capable electrodes historically traded hydrogen control for AC compatibility; 7018-AC RSP maintains full low-hydrogen classification.
- Construction sites with AC-only transformer-based welding machines — building structural steel, pre-engineered metal buildings, and infrastructure work where the site transformer machine is AC.
- Multi-operator AC welding systems — multi-operator transformer welders supply AC to multiple weld stations simultaneously; 7018-AC RSP runs on each station without the arc instability that plagues standard E7018 on AC multi-operator systems.
- Rural and remote operations with AC engine-driven welders — some engine-driven welders supply AC output for stick welding; 7018-AC RSP is the specified low-hydrogen rod for these machines.
- Structural fabrication shops with AC-only machine fleets — shops that have not upgraded to DC inverters and still operate AC transformer machines benefit from 7018-AC RSP over standard E7018 on AC.
- General structural fabrication per AWS D1.1 — any D1.1 application where low-hydrogen filler is required and the machine is AC.
- Repair and maintenance welding on AC machines in field environments — bridge repair, highway infrastructure maintenance, and field structural welding with AC machines.
| Diameter | Amperage (AC) | Amperage (DCEP) |
|---|---|---|
| 3/32 in | 65–100 A | 60–90 A |
| 1/8 in | 90–140 A | 85–130 A |
| 5/32 in | 120–175 A | 115–165 A |
| 3/16 in | 160–225 A | 155–215 A |
AC machine OCV: 7018-AC RSP is designed to run reliably on AC machines with OCV as low as 50–55 V, compared to 70+ V typically needed for standard E7018 on AC. This enables use on older or smaller transformer machines that cannot support standard E7018. Set OCV to maximum available setting on the machine for best arc starts.
Arc length: Short arc is still essential for low-hydrogen performance — 1/2 to 1× core diameter. The potassium stabilizers improve AC re-ignition but a long arc still introduces porosity risk through atmospheric nitrogen pickup.
Position technique:
- Flat/horizontal: Straight stringer or slight weave; 5–15° drag angle.
- Vertical-up: J-weave or triangular weave; reduce amperage 10–15 A below midrange.
- Overhead: Low end of amperage range; short arc; forehand technique.
7018-AC RSP follows the same low-hydrogen storage protocol as all E7018 classifications:
- Sealed container storage: Indefinite shelf life in original sealed Lincoln container in a dry area.
- Holding oven (mandatory once opened): 250–300 °F. Do not leave opened canisters unattended in shop environments overnight.
- Redrying: If moisture-exposed, dry at 700–800 °F for 1 hour. This is required — not optional — for H-rated electrodes.
- AWS D1.1 exposure limits: Follow Table 4.7 time limits for E7018 (without H4R designation unless confirmed by the packaging) — typically 4 hours maximum in low-humidity environments, less in high-humidity.
- ASTM A36 structural steel
- ASTM A572 Grades 42, 50, 60, 65
- ASTM A516 Grades 55, 60, 65, 70
- ASTM A709 Grades 36 and 50 (bridge plate)
All groove and fillet joint types in all positions. Same structural code applicability as standard E7018 under AWS D1.1. The AC optimization does not change the structural chemistry or code classification of the electrode — it only improves AC performance.
Q: Why does standard E7018 perform poorly on AC and what does 7018-AC fix?
Standard E7018 uses sodium-based flux stabilizers. Sodium has a high ionization potential, meaning it does not re-ionize easily at the zero-crossing of a 60 Hz AC waveform. At each polarity reversal, the arc briefly extinguishes and must re-start — sodium flux can fail this re-ignition, causing sputtering, sticking, or arc extinction. Potassium has a significantly lower ionization potential and re-ionizes quickly at the AC zero crossing, maintaining a smooth, continuous arc. Lincoln 7018-AC RSP uses potassium-enhanced stabilizers to solve exactly this AC re-ignition problem.
Q: Can I run 7018-AC RSP on a DC machine?
Yes. 7018-AC RSP runs well on DCEP as well as AC. The potassium stabilizers do not negatively affect DCEP performance. If you have both AC and DC machines in your shop, 7018-AC RSP works on all of them.
Q: What minimum OCV do I need for 7018-AC RSP?
7018-AC RSP is designed for AC machines with OCV as low as 50–55 V, compared to 70+ V typically required for standard E7018. Most AC transformers in the 225–300 A range achieve 55–80 V OCV — verify your machine's OCV against Lincoln's minimum recommendation before use.
Q: Is 7018-AC RSP a low-hydrogen electrode?
Yes. 7018-AC RSP is a classified E7018 electrode and meets low-hydrogen requirements per AWS A5.1. It requires 250–300 °F holding oven storage once the container is opened, identical to standard E7018. The AC optimization does not affect hydrogen classification — the rod must be stored in an oven like any other E7018.
Q: What does RSP stand for in the electrode name?
RSP stands for Rotary Slag Peeling. It refers to the slag's engineered tendency to peel away from the weld bead rapidly and cleanly as the weld cools — without requiring aggressive chipping. This is particularly useful in production environments where inter-pass slag removal time is a bottleneck. The slag literally rolls or peels back as it contracts, reducing cleanup time between passes.
Q: Does 7018-AC RSP meet AWS D1.1 requirements for Low Hydrogen welds?
Yes. 7018-AC RSP is an E7018 classification and is listed in AWS D1.1 Table 4.5 as an approved electrode for Group I and II base metals in prequalified WPS. It meets the Low Hydrogen designation required for Category F and H weld positions in D1.1.
Q: When should I use 7018-AC RSP instead of Excalibur 7018 MR?
Use 7018-AC RSP when your primary concern is AC machine performance — when you're running an AC transformer, AC multi-operator system, or AC engine-driven welder and standard E7018 produces arc instability. Use Excalibur 7018 MR when H4R moisture-resistant credentials, premium arc quality, and Demand Critical weld applications are the priority. Both are excellent structural electrodes for their respective use cases.
The physics of AC arc stability in SMAW is fundamentally different from DC arc maintenance. In DC welding, the arc is sustained continuously by thermal ionization of the arc column between electrode and workpiece. In AC welding, the arc extinguishes at each zero crossing of the 60 Hz cycle — that is, 120 times per second. Re-ignition depends on the presence of easily ionized species in the arc column at the moment the polarity reverses. Sodium compounds, used as arc stabilizers in many E7018 formulations, have an ionization energy of 5.14 eV — adequate for DC but marginal for AC re-ignition. Potassium compounds, with an ionization energy of only 4.34 eV, re-ionize significantly more easily at the AC zero crossing, providing reliable arc re-ignition 120 times per second. Lincoln 7018-AC RSP is formulated with potassium-based flux stabilizers that ensure consistent re-ignition even on AC machines with moderate open-circuit voltage (55–70 V OCV range). The RSP (Rotary Slag Peeling) technology complements the AC performance: the slag undergoes controlled thermal contraction upon cooling that generates a rotary-shear motion at the slag-weld-metal interface, lifting the slag cleanly rather than requiring aggressive chipping. This is particularly valuable in multi-pass AC production welding where slag trapping between passes is a quality risk. For AWS D1.1 structural applications on AC machines, 7018-AC RSP provides the complete Low Hydrogen, CVN-rated, all-position performance of E7018 with optimized AC arc characteristics.