1. First: Thorough Rust Removal (Choose based on rust severity)
Light rust (thin, powdery rust with no pitting): Use 120–180 grit sandpaper, a wire brush (manual or electric), or a sanding block to gently polish the cut surface until the bright metal texture is exposed. Then wipe the surface with a clean cloth dipped in ethanol or acetone to remove oil stains, and dry it immediately.
Moderate rust (thick rust layer with slight pitting): Use an electric angle grinder with a 120-grit flap disc or wire wheel to remove rust and scale, focusing on pitted areas to avoid residual rust. Alternatively, apply a water-based neutral rust remover (pH 6–8), let it sit for 5–10 minutes (follow the manufacturer's instructions), rinse thoroughly with clean water, and dry within 30 minutes.
Severe rust (deep pitting with thick scale): Use dry sandblasting (80–100 grit quartz sand or aluminum oxide) to blast the cut surface-this efficiently removes rust/scale and creates a slightly rough surface for better coating adhesion. After sandblasting, blow off residual sand with compressed air and wipe with ethanol to remove dust.
2. Second: Anti-Rust Treatment (Match to your scenario)
Outdoor use (e.g., structural parts): Use weathering steel-specific coatings-such as polyurethane weather-resistant paint, fluorocarbon paint, or inorganic zinc-rich primer (zinc content ≥ 85%). Apply 1–2 coats (spraying for even coverage); the first coat (primer) should be ~30 μm thick, the second (topcoat) ~40 μm. Let each coat cure fully (e.g., polyurethane paint takes ~24 hours to fully cure at 25°C).
Indoor/short-term storage (≤ 1 year): Apply a thin layer of neutral anti-rust oil/wax to the cut surface with a clean cloth, or wrap the edge with VCI (Volatile Corrosion Inhibitor) film/paper. Wipe off the oil/wax or remove the VCI wrap before formal use.
Decorative scenarios (visible cut surfaces): After sandblasting, immerse the edge in an eco-friendly, chromium-free weathering steel passivation solution for 10–15 minutes to accelerate dense oxide film formation. Rinse with deionized water, dry, and apply a transparent fluorocarbon clear coat (~30 μm thick) to preserve the rusty texture while preventing further rust.
3. Third: Preventive Measures (Avoid future rust)
Prioritize laser/plasma cutting (low heat input) over flame cutting (which creates a thick oxide layer). If using flame cutting, trim the oxidized edge with a grinder immediately.
Store cut plates in a dry, well-ventilated area (avoid rain/high humidity). Stack with spacers (e.g., wooden blocks) for air circulation.
For outdoor plates, inspect the cut surface every 6–12 months. Touch up peeling coatings or rust spots promptly (local rust removal + re-coating).
