The combination of E6010 for the root pass and E7018 for fill and cap passes is one of the most common SMAW practices in structural steel fabrication. E6010 offers deep penetration and excellent arc control in tight, open-root groove welds — qualities that E7018 does not match for root pass work. E7018 offers low hydrogen, excellent mechanical properties, and high deposition for filling and capping — qualities that go to waste on a root pass.
The combination works precisely because the two electrodes are optimized for different pass types. The WPS documentation challenge is ensuring the procedure covers both electrode classifications with a properly structured PQR behind it.
Why E6010 for root passes
E6010 (AWS A5.1, DCEP) is a cellulosic electrode characterized by a highly active, penetrating arc and a fluid, fast-freezing slag. Those properties make it the standard choice for open-root groove welds:
The forceful arc drives into the root opening and washes the root edges, supporting good fusion at the root face without burn-through
The fast-freezing slag supports the weld pool in vertical and overhead positions without sagging
The arc is easy to restart, which matters when welding around the joint is interrupted
The rod runs well in tight grooves where electrode angle is constrained
The cellulosic electrode coating produces high diffusible hydrogen — typically 15–30 mL/100g by the IIW method. This is why E6010 is categorized as a non-low-hydrogen electrode and why it is not acceptable as the only electrode on joints requiring low-hydrogen filler metal, such as high-restraint connections or high-strength steels where hydrogen cracking is a primary concern.
E6011 (AC-capable) and E6010 share similar penetrating arc characteristics. E6011 is sometimes specified where only AC welding machines are available, but E6010 on DCEP remains the standard for structural root passes.
Why E7018 for fill and cap passes
E7018 (AWS A5.1, DCEP) is a low-hydrogen, iron-powder electrode with H4 or H8 diffusible hydrogen levels when handled per manufacturer requirements. It deposits a clean, fluid weld pool with good sidewall wash and produces a flat-to-slightly-convex bead profile well-suited to filling a groove cavity efficiently.
For fill and cap passes where the constraint of the root opening no longer applies and deposition rate matters, E7018 is the workhorse:
Low hydrogen eliminates the hydrogen cracking risk that would otherwise accumulate in a multi-pass weld as hydrogen diffuses through the joint
Iron powder in the coating increases deposition rate compared to E6010
The slag is heavier and less fluid than E6010, which is acceptable in fill passes where the slag is on top of a supported bead rather than at the bottom of a groove
The tradeoff — E7018's sluggish arc is poor for root pass work in open-root joints — is exactly what E6010 overcomes in the first pass.
Essential variable implications under AWS D1.1:2025
AWS D1.1:2025 Table 6.6 governs essential variables for SMAW procedures. Filler metal AWS classification is an essential variable for SMAW — that is, changing the electrode classification from what is recorded on the PQR is a requalification trigger.
If a WPS lists only E7018 and a welder uses E6010 for the root pass, that is a deviation from the qualified WPS and is not code-compliant, regardless of whether the E6010 root pass is otherwise sound. The essential variable has changed without authorization.
The correct approach: the WPS must list both electrode classifications:
Root pass: E6010, per SMAW process
Fill and cap passes: E7018, per SMAW process (low-hydrogen, H4 or H8)
And the PQR that supports the WPS must reflect both classications used during the qualification test.
The most common and practical approach is to run one PQR test that replicates production practice: E6010 for the root pass, E7018 for fill and cap passes. The test welder makes the root pass with E6010, cleans, and completes the joint with E7018. All PQR test specimens — tensile, guided bend, or macro as applicable — are taken from the completed multi-pass test weld.
This single PQR then qualifies a WPS that lists both electrode classifications. Because the test weld itself was made with both electrodes, the qualification is directly supported by a realistic test.
Two separate PQRs combined in a single WPS
Some shops already have a PQR for E7018 groove weld qualification from prior work. If they want to add E6010 root pass coverage without re-running the full test, they need a second PQR that includes E6010 as the root electrode and references the E7018 fill. AWS D1.1 permits a WPS to be supported by more than one PQR, and the WPS can reference both documents.
One concern with the E6010 + E7018 combination is the hydrogen contributed by the cellulosic root electrode. Hydrogen cracking (cold cracking) is a time-delayed failure mode driven by: diffusible hydrogen in the weld metal, tensile residual stress, and susceptible microstructure in the heat-affected zone.
Managing hydrogen risk with E6010 roots:
Maintain adequate preheat. The same preheat required for the E7018 fill passes applies to the E6010 root pass. Do not reduce preheat just because the root electrode is being used. If anything, the cellulosic electrode argues for careful attention to preheat, since the hydrogen burden is higher.
Complete the weld in sequence. Do not leave an E6010 root pass in a joint open overnight without depositing fill passes. The root bead is thin and cools quickly; hydrogen that diffuses toward the fusion line finds a stress concentration at the root face geometry. Completing the fill with low-hydrogen E7018 covers the root and establishes a larger heat sink that keeps the joint above the critical cooling rate for hydrogen diffusion.
Use E6010 only for the root pass. The WPS should specify E6010 for root pass only. There is no reason to run E6010 in fill or cap passes where E7018's properties are superior and its use eliminates hydrogen concern.
Document electrode storage. E6010 does not require oven storage the way E7018 does — the cellulosic coating is not hygroscopic in the same way. However, E7018 electrodes for fill passes must be stored and handled per AWS D1.1:2025 low-hydrogen requirements (sealed containers, stabilization ovens, exposure time limits). The WPS and electrode control procedure should address both electrode types.
WPS documentation checklist for E6010 + E7018 combination
A WPS covering this combination should address all of the following:
Process: SMAW (single process, two electrode classifications)
Root pass electrode: E6010, specific diameter(s) qualified, DCEP
Fill and cap electrode: E7018, specific diameter(s) qualified, DCEP, low-hydrogen designation (H4 or H8 preferred)
Minimum preheat: per AWS D1.1:2025 for the base metal specification, thickness, and heat input
Maximum interpass temperature: typically 550°F (290°C) for common structural steels unless the WPS specifies otherwise
Joint design and configuration: groove type, root opening range, land dimension, groove angle — must match the PQR test geometry within the qualification range
Positions qualified: from the PQR
Backing: steel or none — one test, one position in the PQR
The finished WPS should be clear that E6010 is the root electrode and E7018 is the fill/cap electrode. Ambiguity in this specification leads to welders using E6010 throughout, which is not prohibited but adds unnecessary hydrogen burden, or E7018 for the root, which often produces a cold, convex root bead with poor fusion to the root faces.
WPS Welding structures the WPS form to capture multi-electrode sequences in a single document, linking the root electrode and fill electrode to their respective passes with the correct essential variable fields.
Rule library based on AWS D1.1:2025; verify against your governing edition.
FAQ
Frequently asked.
Can a single WPS cover both E6010 root and E7018 fill passes?
Yes. A single WPS can and typically should cover both electrode classifications when the intent is to use E6010 for the root pass and E7018 for fill and cap. The WPS must list both electrode AWS classifications, specify which classification is used for which pass type, and the supporting PQR must qualify both. Running the PQR test using E6010 root + E7018 fill replicates production practice and provides a single qualification document for the combination.
Does changing from E6010 to E7018 mid-weld require a new WPS under AWS D1.1?
No, not if the WPS already covers both electrode classifications. AWS D1.1:2025 Table 6.6 lists electrode classification as an essential variable for SMAW. This means changing to an electrode not listed in the qualified WPS is a requalification trigger. But if both E6010 and E7018 are listed in the WPS (with PQR qualification covering both), there is no code barrier to using them in sequence.
Can E6010 and E7018 be used in the same AWS base metal group and material?
Both E6010 and E7018 are approved for use on prequalified base metals in AWS D1.1 Table 6.9 groups. E6010 (A5.1) is a cellulosic electrode approved for structural use; E7018 (A5.1) is a low-hydrogen electrode. Both may be used on A36, A572, A992, and other common structural steels. The filler metal selection and matching to base metal strength group is the same regardless of whether the electrodes are used in sequence.
What hydrogen level does E6010 introduce in a root pass?
E6010 is a cellulosic (non-low-hydrogen) electrode with typical diffusible hydrogen levels of H16 or higher. When preheat is maintained and the root bead is thin (as is typical on root passes), hydrogen cracking risk is managed. The key is adequate preheat per AWS D1.1:2025 and immediate follow-up with E7018 fill passes — which are low-hydrogen — before the joint cools. Leaving an E6010 root in a thick joint overnight without completing the fill is a hydrogen cracking risk.