Shielded metal arc welding (SMAW) may be the oldest arc welding process in commercial use, but electrode selection still trips up experienced fabricators when they move to new base metals, new joint configurations, or new code editions. AWS D1.1:2025 has specific requirements about which SMAW electrodes are preapproved and for what applications — getting this right before writing the WPS saves requalification costs.
This article focuses on the four electrodes that account for the large majority of structural SMAW work: E6010, E6013, E7016, and E7018. Understanding the differences — chemically, mechanically, and code-wise — is a prerequisite for building a WPS that survives audit.
The cellulosic vs. low-hydrogen divide
SMAW electrode coatings fall into two broad families based on their chemistry and moisture content:
Cellulosic coatings (E6010, E6011, E6013) contain high amounts of cellulose in the flux, which produces a deep-penetrating, forceful arc with high hydrogen levels in the weld deposit. The high hydrogen is a feature, not a bug — it improves arc penetration through mill scale and rust, making these electrodes excellent for root passes in open-root joints and field repair on less-than-ideal surfaces. But that same hydrogen creates cracking risk in susceptible base metals.
Low-hydrogen coatings (E7016, E7018, E8018, E9018) use a lime-fluoride (basic) flux with minimal moisture-bearing compounds. The result: much lower diffusible hydrogen levels in the deposit. These electrodes require dry storage and, for some alloys, pre-baking before use — but they are the required choice for most structural steel above A36 grade.
The dividing line in AWS D1.1:2025 is not the electrode type alone — it is the combination of electrode type and base metal properties. The code's preheat requirements in Clause 7 (or the applicable table) reference base metal category and carbon equivalent, which then reference process hydrogen level. Low-hydrogen process is typically required when carbon equivalent rises above a threshold and base metal thickness or restraint is significant.
E6010: the root pass workhorse
E6010 is a cellulosic electrode classified for use on DC+ (DCEP) only. Its characteristics:
- Penetration: The cellulosic arc drives deep into the joint root, bridging gaps and fusing root faces even in less-than-perfect fit-up.
- Positional capability: All-position (1G, 2G, 3G, 4G, 1F through 4F), making it useful for field work and out-of-position joints.
- Surface tolerance: Performs better than low-hydrogen electrodes on surface contamination — rust, mill scale, zinc primer — because the aggressive arc burns through surface films.
- Slag characteristics: Thin slag that is easy to remove; the weld face is somewhat coarse but adequate for root pass quality.
Where E6010 fits in AWS D1.1:2025: E6010 is preapproved in AWS D1.1:2025 for SMAW root passes in CJP groove welds, particularly where open-root technique is used with back-side access for back gouging or where steel backing will be left in place. Verify the specific filler metal preapproval table in the 2025 edition for your joint type.
Where E6010 does not fit: On higher-strength steels (A514, A709 HPS 70W, A913 Grade 65+), the cellulosic hydrogen level is incompatible with the base metal's HAZ sensitivity. E6010 root passes on these materials require preheat levels that negate the fit-up forgiveness advantage, and low-hydrogen fill and cap passes create a procedure complication. For high-strength structural steel, the better practice is to use low-hydrogen electrodes throughout — an E7018 or E8018 root on a cleaner joint with tighter tolerances.
E6011: Similar to E6010 but AC-compatible. Sees limited use in structural fab where DC machines are standard. Same hydrogen concerns apply.
E6013: Often labeled "general purpose" and marketed as easy-starting. The coating produces low penetration and a smooth, cosmetic bead — useful for thin sheet metal and light fitment, not appropriate for structural groove welds. AWS D1.1:2025 does not list E6013 as a preapproved filler for prequalified structural WPS. Avoid E6013 in structural applications.
E7016 and E7018: the low-hydrogen pair
Both E7016 and E7018 are low-hydrogen electrodes delivering 70 ksi (480 MPa) minimum tensile strength in the deposit. The critical difference is the coating:
E7016 (low-hydrogen potassium): The potassium-bearing flux allows operation on both AC and DC+. Deposition efficiency is moderate. Common in situations where only AC power is available — older field machines, remote generators. Less common in production shops with DC equipment.
E7018 (low-hydrogen potassium, iron powder): The iron powder addition increases deposition efficiency and makes E7018 the production favorite. The smooth arc and fast deposition rate reduce labor cost per foot of weld. Requires DC+ in most applications, though some E7018 classifications are AC-rated.
For structural SMAW WPS development on A36, A572, and A992, E7018 is the default electrode choice in nearly every shop. The WPS should specify the classification (E7018 or E7018-1 for improved notch toughness), the applicable AWS A5.1 or A5.5 specification, and the hydrogen designator (H4, H8, or H16) when a low-hydrogen requirement applies.
E7018-1 is a variant with improved Charpy V-Notch impact requirements — specified where CVN testing is required per AWS D1.1:2025 Table 6.8 supplementary essential variables. If your project invokes CVN supplementary essentials under Table 6.8, verify that your electrode classification meets the CVN requirements for the test temperature.