Maintaining the surface patina of Q355NH weathering steel screens is all about keeping it uniform, stable, non-flaking, and free from discoloration or rust streaks. Here's the practical, on-site maintenance method:
1. Apply a transparent matte protective coating (most critical)
Once the patina reaches your ideal color (deep brown / chocolate brown):
Spray or brush with matte acrylic varnish, polyurethane clear coat, or special weathering steel protective oil
Isolates air, moisture, dust, and UV rays
Stops the patina from getting darker and locks the color
Reapply every 3–5 years
2. Regular gentle cleaning
Rinse with clean water every 3–6 months to remove dust, leaves, and flying dirt
Use a soft cloth or soft brush; do not scrub hard
Avoid high-pressure water jets that may damage the patina
Never use strong acid/alkali cleaners
3. Prevent water retention and rust streaks
Ensure the screen has good ventilation and drainage
Avoid long-term waterlogging in gaps or frames
Keep the surface dry to prevent light-colored water stains and dark streaks
4. Avoid contact with corrosive substances
Do not let cement, lime, soil, or wet wood stick to the surface
Isolate from dissimilar metals (stainless steel, aluminum) with rubber gaskets
Keep away from chemical fumes, oil pollution, and strong acid/alkali environments
5. Timely minor repairs
For small scratches or partial discoloration:Lightly sand → spot-spray a small amount of weathering steel accelerant → re-coat with transparent finish
For flaking or damaged patina:Clean the loose layer → re-form uniform patina → seal again
6. Keep away from long-term damp and closed environments
Q355NH needs wet-dry cycles to maintain a stable patina
Long-term dampness will make the surface powdery and uneven
