1. Pre-Welding Preparation
Surface Cleaning:
Remove the protective patina (rust layer) near weld zones using grinding or brushing.
Eliminate mill scale, oil, and moisture to avoid porosity.
Preheating (If Needed):
For thick sections (>20mm), preheat to 100–150°C to prevent cracking (due to high carbon equivalent, CE).
2. Welding Methods & Materials
(A) Recommended Processes:
Shielded Metal Arc Welding (SMAW):
Common for fieldwork (e.g., bridges).
Gas Metal Arc Welding (GMAW/MIG):
Better for controlled environments.
Flux-Cored Arc Welding (FCAW):
Suitable for outdoor, windy conditions.
(B) Filler Metal Selection:
Match Base Metal:
Use low-alloy electrodes (e.g., AWS E7018-W for ASTM A588).
Stainless steel fillers (309L/312) for dissimilar metal joints.
Key Properties:
Higher Ni/Cr content to replicate weathering resistance.
3. Post-Welding Treatments
• Slag Removal:
◦ Clean weld slag to avoid crevice corrosion.
• Patina Restoration:
◦ Allow natural rusting or accelerate with salt spray/cyclic wet-dry exposure.
• Avoid Paint Unless Necessary:
◦ If painted, use breathable coatings to avoid trapping moisture.
