Question 1: Why do the edges of pre-coated steel coils require special treatment?
After pre-coated steel coils are cut, very fragile "cut edges" are left. The coating is damaged here, exposing the metal substrate directly, which is the starting point for future corrosion. If left untreated, rust will spread beneath the coating, causing blistering and peeling, severely affecting the lifespan and appearance.
Second question: What are the core edge finishing methods and accessories?
Edge finishing of color-coated steel sheets mainly involves two methods: covering and sealing, and physical folding, used in conjunction with specialized accessories.
Treatment Methods | Specific Measures | Applicable Scenarios
🧴 Sealing Application | Sealant/Tape: Apply a neutral, UV-resistant special sealant (such as silicone sealant) to the cut and overlap areas. Molded foam sealing strips can also be used in areas such as eaves for sealing and waterproofing.
Special Rust-Preventive Paint/Coating Repair: Apply a matching rust-preventive paint to the cut edges of the sheet (i.e., "edge sealing"), which is an economical and effective method. Suitable for exposed cut edges, sheet overlaps, and screw fixing points.
Three key questions: What are the core points for specific construction?
**Proper Cutting and Protection:** Use electric shears or hand shears whenever possible, keeping the blade sharp. Avoid burrs; a more economical method is to apply rust-preventive paint to the cut edges.
**Firm Overlaps and Reliable Sealing:** The longitudinal overlap length of roof panels should be no less than 200mm, and wall panels no less than 100mm. For low-corrugated panels, the overlap length should not be less than 250mm. Sealant or sealing strips must be used at the overlap points, and the overlap width for flashing should be no less than 150mm.
**Precise Tightening to Avoid Damage:** Screws must be driven in vertically, 15-20mm from the edge of the panel, and must not be tilted. The tightness should be such that the washer is slightly compressed but the panel surface does not deform.
**Frequent Cleaning and Inspection:** Clean up metal debris promptly after installation, and regularly check the condition of screws and coatings. Repair any problems immediately.
Fourth Question: When should the edge finishing process be performed?
The edge finishing process can be performed before or after board installation, each with its own advantages and disadvantages:
Pre-installation edge finishing: The edges are pre-folded before the boards are laid, making the operation more convenient and efficient.
Post-installation edge finishing: Special tools are used on-site to bend the edges, but after cutting, approximately 50mm of allowance must be left at the top of the board. This is subject to site conditions and often requires the use of edge finishing strips.
Five Questions: What to do if there are problems with the edge trim?
Edge trim too short: It is generally not recommended to force it flat (e.g., pressing a 90° trim to 180°), as this can cause metal fatigue or even breakage. A slightly longer new trim should be made, or an "I"-shaped joint should be used for overlap.
Coating damage or minor rust: First, clean the area with fine sandpaper, then apply a special repair coating and matching primer to prevent the rust from spreading.
Edge trim misalignment or incorrect angle: If the misalignment is minor, it can be removed and repositioned; if the hole deviation is large, the old hole needs to be filled with sealant and a new hole drilled for fixing.
Water leakage: Locate the leakage point, remove the expired sealant, reapply a neutral, mildew-resistant, and weather-resistant sealant, or reinforce the seal with sealing tape.