1. MIG Welding Corten: Key Considerations
A. Filler Wire Selection
AWS ER70S-6: Common for mild steel, but may not match Corten's weathering properties.
Weathering-Specific Wires:
AWS ER80S-Ni2 (for ASTM A588 Corten) – Better corrosion resistance.
ER90S-G (high-strength option).
Stainless Steel 309L – Used for dissimilar joints (e.g., Corten to stainless).
B. Shielding Gas
75% Argon + 25% CO₂ (C25): Standard for clean, stable welds.
Avoid 100% CO₂ – Increases spatter and oxidation risk.
C. Preheating & Interpass Temperature
Preheat: 150–200°C (300–400°F) for thick sections (>20mm) to prevent cracking.
Interpass Temp: Keep below 250°C (480°F).
D. Post-Weld Treatment
No stress relief needed for most Corten grades.
Wire-brush welds to remove slag and promote even patina formation.
2. Challenges & Solutions
| Issue | Cause | Fix |
|---|---|---|
| Cracking | High hardness, hydrogen embrittlement | Preheat, low-hydrogen rods, slow cooling |
| Uneven Patina | Welds rust differently than base metal | Use weathering-grade filler, sand/brush blend |
| Porosity | Moisture in shielding gas or wire | Dry storage, gas flow check (20–25 CFH) |
3. Best Practices
Cleanliness: Remove mill scale, oil, and rust before welding.
Travel Speed: Moderate to avoid excessive heat input.
Test Welds: Verify settings on scrap Corten first.
4. When to Avoid MIG Welding Corten
Critical structural joints: Consider SMAW (stick) or FCAW for better penetration.
Saltwater/marine environments: Use stainless filler (309L) for corrosion resistance.
