The golden rule: match the filler to the base metal's composition and strength. The second rule: when in doubt between two wires, read the alloy numbers again — 308 and 316 are not interchangeable.
ER = electrode/rod; S = solid wire, T = tubular (flux-cored). The numbers carry tensile strength (70 = 70 ksi) and the letter/numbers the composition.
| Filler | Process | Matches Base Metals | Key Features | Typical Applications |
|---|---|---|---|---|
| ER70S-6 | GMAW | A36, A572, most mild & low-alloy carbon steel | High Si/Mn deoxidizers — tolerant of light mill scale and rust | General fabrication, structural, auto repair, 75/25 gas |
| ER70S-2 | GMAW | Mild steel, HSLA; thin galvanized (vented) | Triple-deoxidized (Al, Ti, Zr) — the dirty/rusty steel wire | Repair work, contaminated surfaces, outdoor tanks |
| ER80S-D2 | GMAW | HSLA steel, 80 ksi grades (e.g., A514-type base) | Mn-Mo wire, 80 ksi tensile, crack-resistant | Heavy equipment, pressure piping, 80 ksi weldments |
| ER308L | GTAW / GMAW | 304, 304L, 308 base stainless | L-grade (low carbon) resists chromium-carbide sensitization | Food, dairy, brewery, chemical processing |
| ER309L | GTAW / GMAW | Dissimilar: carbon steel ↔ stainless; 309 base; cladding | High alloy content absorbs dilution from steel side | Transition joints, stainless overlay / cladding |
| ER316L | GTAW / GMAW | 316, 316L base stainless | Mo addition boosts pitting and chloride resistance | Marine, chemical, pharmaceutical piping |
| ER4043 | GTAW / GMAW | Aluminum 6061, 6063, 3003, many castings | 5% Si — lower melting point, fluid, crack-resistant, colors gray when anodized | General aluminum fab, extrusions, radiators, castings |
| ER5356 | GTAW / GMAW | Aluminum 5052, 5083, 5086, 5454 (5xxx marine) | 5% Mg — higher strength than 4043, better corrosion resistance | Salt-water environments, boat hulls, tanks, dump bodies |
| E71T-1 | FCAW (gas) | A36, A572, carbon steel | Flux-cored, 71 ksi, high deposition, wind-tolerant | Structural, heavy fab, shipbuilding — 75/25 or CO2 |
The mistakes that show up on X-ray reports and cracked welds.
A 316 flange welded with 308 loses the molybdenum protection. Match the base: 316 gets 316L filler, 304 gets 308L.
Welding carbon steel directly to stainless with 308 produces a brittle, crack-prone martensitic zone. 309L handles the dilution — it's the only right answer for transition joints.
6061 accepts 4043 (easy, crack-resistant) or 5356 (stronger, ~30% more tensile). Marine 5xxx aluminum must use 5356 — 4043 has no place in salt water.
The "4" in 4043 and "5" in 5356 are the same first digits used in base alloy families: 4xxx bases (like 4043) are silicon alloys, 5xxx bases (like 5052) are magnesium alloys. Match the family and you're already most of the way home.
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