ER70S-3 vs ER70S-6: Clean Steel Wire vs All-Purpose Wire
Same wire, different deoxidizer levels. ER70S-6 handles dirty steel better and is what 90% of shops stock. ER70S-3 leaves a cleaner surface when your steel is already clean. If you are not sure, buy ER70S-6.
ER70S-3: Base metal is clean and properly prepared. ER70S-6: You are doing general shop welding where base metal cleanliness varies.
Which One Should You Use?
Pick ER70S-3 if:
Base metal is clean and properly prepared. You need minimal silicon deposits for cosmetic or coating reasons. The application specification calls for ER70S-3 specifically.
Runs on DCEP, 40-340A range. ER70S-3 full amperage chart
Pick ER70S-6 if:
You are doing general shop welding where base metal cleanliness varies. You want a single wire that handles most mild steel applications. You are ordering from standard stock without specialty requirements.
Runs on DCEP, 30-350A range. ER70S-6 full amperage chart
Side by Side
| Attribute | ER70S-3 | ER70S-6 |
|---|---|---|
| Manganese content | 0.90 - 1.40% | 1.40 - 1.85% |
| Silicon content | 0.45 - 0.75% | 0.80 - 1.15% |
| Contaminant tolerance | Requires clean base metal | Tolerates moderate rust, oil, mill scale |
| Silicon island deposits | Minimal | More common, small glassy spots on bead |
| Weld pool fluidity | Standard | More fluid, better wetting |
| Market availability | Less common, specialty orders | Universally stocked, industry standard |
Settings at a Glance
Machine settings and operating characteristics side by side. For full amperage charts, see the individual electrode pages.
| Setting | ER70S-3 | ER70S-6 |
|---|---|---|
| Polarity | DCEP | DCEP |
| Positions | flat, horizontal, vertical-up, overhead | flat, horizontal, vertical-up, overhead |
| Penetration | medium | medium |
| Coating | copper-coated solid wire | copper-coated solid wire |
| Amps at 0.030" | 40-140A | 40-145A |
| Amps at 0.035" | 50-210A | 50-220A |
| Amps at 0.045" | 75-340A | 75-350A |
How ER70S-3 and ER70S-6 Work Together
The real-world difference comes down to how much cleanup you want to do. ER70S-6 leaves a glassy silicon residue (called silicon islands) on the weld surface. On carbon steel that gets painted, this is not a problem. On stainless or on visible welds where surface finish matters, ER70S-3 produces a cleaner result. Most shops default to ER70S-6 because it handles light mill scale and surface contamination better, and the cleanup difference is not worth stocking two spools.
Common Mistake With ER70S-3
Specifying ER70S-3 for outdoor structural work or on steel with any surface contamination. ER70S-3 has lower deoxidizer content, which means it is less forgiving of surface impurities. If your steel has any mill scale, light rust, or oil residue, ER70S-6 is the safer choice. ER70S-3 is for clean steel in controlled environments.
Practical Differences
| Factor | ER70S-3 | ER70S-6 |
|---|---|---|
| Common Brands | SuperArc L-50, HB-25 | SuperArc L-56, HB-28 |
Where to Buy
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ER70S-3 vs ER70S-6: Common Questions
Which is better, ER70S-3 or ER70S-6?
Different rods for different jobs. Key differences: Manganese content: ER70S-3 has 0.90 - 1.40%, while ER70S-6 has 1.40 - 1.85%. Silicon content: ER70S-3 has 0.45 - 0.75%, while ER70S-6 has 0.80 - 1.15%. Contaminant tolerance: ER70S-3 has requires clean base metal, while ER70S-6 has tolerates moderate rust, oil, mill scale. Match the rod to the work, not the other way around.
Can I substitute ER70S-3 for ER70S-6?
Not a straight swap.
Can I use both ER70S-3 and ER70S-6 on the same joint?
The real-world difference comes down to how much cleanup you want to do. ER70S-6 leaves a glassy silicon residue (called silicon islands) on the weld surface. On carbon steel that gets painted, this is not a problem. On stainless or on visible welds where surface finish matters, ER70S-3 produces a cleaner result. Most shops default to ER70S-6 because it handles light mill scale and surface contamination better, and the cleanup difference is not worth stocking two spools.
Reference data only. Verify all settings against manufacturer documentation and the applicable welding code before use. Amperage ranges are starting points that vary by position, fit-up, and material. Welding involves serious injury risks including burns, electric shock, fume exposure, and fire. This site does not replace proper training, certification, or employer safety procedures. See full terms of use.
Data sourced from AWS A5.18/A5.18M.