The self-protective rust layer is the core of Corten Steel's corrosion resistance. During long-term use, improper environment or mechanical damage may lead to rust layer failure. Accurately judging failure and taking targeted repair measures are crucial to extend service life. This article provides practical guidance for foreign customers.
1. How to Judge Rust Layer Failure
Visual Observation: Normal self-protective rust layer is dense, uniform reddish-brown (α-FeOOH). Failure signs include: uneven rust color (dark spots, yellowish rust), loose rust powder that falls off easily, and visible steel substrate exposure or pitting corrosion.
Simple Tests: ① Tape test (ASTM D3359): Stick pressure-sensitive tape on the rust layer and tear it off quickly-obvious rust powder on the tape indicates failure. ② Rub test: Rub the surface with a dry cotton cloth; continuous rust powder shedding means poor stability.
Corrosion Rate Monitoring: If the annual corrosion rate exceeds 0.03mm/year (tested by thickness gauge), it indicates the rust layer can no longer block corrosive media, leading to accelerated substrate corrosion.
2. Corresponding Repair Measures
Local Minor Failure (Small-area loose/peeling): ① Clean the failure area with a wire brush or sandpaper to remove loose rust and expose the fresh substrate. ② Apply Corten Steel rust accelerator to the area and cure it in a 70-85% humidity environment for 24-48 hours to form a new dense rust layer. ③ Spray a transparent rust layer curing agent to enhance adhesion.
Large-area Failure (Over 10% of total surface): ① Use sandblasting to completely remove the failed rust layer (surface roughness Ra 3.2-6.3μm). ② Conduct overall artificial rust acceleration treatment (follow the accelerator's instructions) to form a uniform self-protective rust layer. ③ For harsh environments (coastal, industrial areas), add silane impregnation treatment to improve corrosion resistance.
Severe Failure (Substrate pitting/corrosion penetration): ① Cut off the severely corroded parts and replace them with new Corten Steel sheets of the same grade. ② Weld with low-temperature-resistant weathering welding materials (e.g., ER50-GNiCuCr) and grind the weld seam. ③ Perform rust acceleration and curing treatment on the new and welded areas to ensure consistent rust layer performance.
3. Post-Repair Maintenance Suggestions
After repair, inspect the rust layer monthly for the first 6 months. Avoid mechanical impact on the repaired area. For outdoor projects, clean the surface annually to remove dust and corrosive residues, ensuring the repaired rust layer remains stable.
