The "special protection" is a procedural treatment to make the HAZ perform like the parent metal.
1. Thorough Cleaning (Essential):
◦ Action: Immediately after welding, use power tools like needle scalers, grinders, or rotary wire brushes to aggressively remove all welding slag, spatter, and, most importantly, the entire heat-tinted scale from the weld bead and the surrounding HAZ.
◦ Goal: Achieve a clean, bright, bare metal surface. This provides a uniform and stable base for the new patina to form.
2. Surface Profiling (Highly Recommended for Aesthetics):
◦ Action: Grind the weld reinforcement smooth and flush with the base metal.
◦ Goal: This eliminates crevices that trap moisture and removes the most severely altered part of the HAZ on the weld crown. A smooth contour ensures water drains quickly, promoting even wet/dry cycles crucial for patina stability.
3. Patina Reformation (The Active "Healing" Step):
◦ Action: Apply a commercial weathering steel patina accelerator (a chemical solution) to the entire cleaned area (weld and HAZ).
◦ Goal: This solution chemically accelerates the oxidation process, forcing a stable, protective patina to form in days or weeks instead of years. This is the most effective way to ensure the HAZ is "protected" and blends seamlessly with the rest of the structure, both in appearance and corrosion resistance.
