1.What are the core selection principles?
Color-coated steel sheets (coated steel plates) are made by coating colored paint onto the surface of cold-rolled galvanized or aluminum-zinc coated substrates. Their core advantage lies in their superior corrosion resistance. The screws used for connection must form part of the overall corrosion protection system, not be the weakest link. If the screws corrode before the sheet material, it can lead to leaks, loose connections, or even complete failure.
2.What types of screws are recommended?
Best general-purpose choice: Aluminum-zinc plated self-tapping screws
Features: The screw surface has a distinctive bright silver snowflake pattern. It usually comes with a color-matched plastic washer head.
Top-tier option: Stainless steel self-tapping screws
Features: Typically stainless steel in its natural color (matte silver-white).
Model: A2-70 (304 stainless steel) is recommended. For highly corrosive environments (such as coastal areas or chemical plants), consider A4-80 (316 stainless steel).
Available options: High-quality galvanized self-tapping screws
Features: Bright silver or colored zinc coating.
3.What is the function of key functional components?
Waterproof sealing: When the screw is tightened, the washer deforms, fitting tightly against the surface of the color-coated steel sheet to prevent rainwater from seeping in through the screw holes.
Cushioning and scratch protection: Prevents the metal screw head from directly cutting or abrading the color-coated surface.
Electrical insulation: Isolates different metals, reducing the risk of electrochemical corrosion.
Inspection: The washer should be soft, elastic, and resistant to aging (not easily cracking under sunlight).
4.What are the key construction points?
Strictly prohibit mixing: Never use ordinary black carbon steel screws, self-drilling screws (without washers), or any screws without effective sealing washers.
Perpendicular driving: Screws must be driven perpendicular to the panel surface. Driving at an angle will result in a poor seal from the washers, inevitably leading to leaks.
Moderate torque: Use a dedicated electric screwdriver and adjust the torque accordingly. Tighten until the washers are completely flattened and slightly bulging. Do not overtighten, as this may cause the washers to break or the color-coated panel to deform or dent.
Roof: Fix at the crest of the corrugation.
Wall: Usually fix at the trough of the corrugation.
Specific locations must strictly adhere to the design drawings and panel type requirements.
On-site protection: Screws should be stored in a dry place. If any remaining coating on the screw heads is damaged after installation, it can be repaired by applying a dedicated anti-corrosion paint (such as zinc oxide).
5.What are the summary and action steps?
Review the design: First, verify the specific requirements for fasteners in the design drawings or technical specifications.
Match the sheet material: Select the screw material based on the substrate of the color-coated coil (galvanized steel sheet GL or aluminized zinc sheet GL) and the project environment (coastal, industrial area, general inland).
Calculate the length: Determine the screw length using the formula "sheet thickness + purlin thickness + 10mm".
Purchase qualified products: Purchase aluminized zinc self-tapping screws or stainless steel self-tapping screws with complete EPDM sealing washers from reputable channels and obtain quality certification documents.
Standardize construction: Provide technical instructions to workers, emphasizing key points such as vertical driving and torque control.