| 1 | Base Steel Grade | Steel designation, yield strength, tensile strength, elongation, and chemical composition. | Grade and mechanical properties should match the project specification, forming method, and applicable standard. | The substrate affects roll forming, bending performance, structural strength, and service life. | Mill test certificate and independent material inspection report when required. |
| 2 | Metallic Coating Mass | Zinc or zinc-aluminium coating type and coating mass on both sides. | Select the coating mass according to exposure conditions; common commercial specifications include approximately 40–275 g/m² total coating mass. | Higher coating mass generally provides improved corrosion protection, but should be balanced against forming and cost requirements. | Coating test results, product specification, and lot-based inspection records. |
| 3 | Paint System | Primer type, topcoat chemistry, back-coat specification, and total paint-film thickness. | Typical total top-surface paint thickness is about 15–35 μm, depending on the coating system and end use. | The paint system influences UV resistance, color retention, adhesion, flexibility, and corrosion performance. | Technical data sheet, coating-production records, and paint-film thickness measurements. |
| 4 | Dimensional Accuracy | Thickness, width, length, coil weight, flatness, edge condition, and shape tolerances. | Tolerances should be stated in the purchase contract and aligned with the applicable steel standard. | Accurate dimensions reduce slitting waste, installation problems, profiling defects, and production downtime. | Inspection plan, calibration records, dimensional inspection report, and approved sample. |
| 5 | Color and Surface Finish | Color reference, gloss level, texture, minor surface defects, and protective-film requirements. | Use an approved color standard or physical sample; define acceptable gloss and visual tolerance before production. | Consistent appearance is essential for roofing, wall cladding, appliances, doors, and other visible applications. | Approved color panel, spectrophotometer results where applicable, and pre-shipment photos. |
| 6 | Formability and Adhesion | Bend performance, coating adhesion, cracking resistance, and suitability for roll forming or stamping. | Confirm the required bend grade, such as a specified minimum inside-bend radius, before ordering. | Poor formability can cause coating cracks, delamination, edge damage, and premature corrosion. | Bend-test results, adhesion-test records, and production trial samples. |
| 7 | Corrosion and Weather Resistance | Exposure category, humidity, salt contamination, UV intensity, temperature variation, and warranty conditions. | Specify the intended environment and test method; do not select a coating solely by color or nominal paint thickness. | A suitable coating system is critical for coastal, industrial, high-humidity, and high-UV applications. | Corrosion-test data, weathering-test data, product warranty, and application limitations. |
| 8 | Production Capacity and Lead Time | Monthly capacity, minimum order quantity, available widths, production schedule, and delivery reliability. | The supplier should confirm capacity for the complete project volume and provide a written production and shipping schedule. | Reliable supply protects construction schedules and reduces the risk of color or specification changes between batches. | Capacity statement, recent delivery records, production plan, and agreed order milestones. |
| 9 | Packaging and International Logistics | Coil eye orientation, waterproof wrapping, edge protection, pallet or skid design, marking, and loading method. | Packaging should protect against moisture, abrasion, deformation, and handling damage during multimodal transport. | Correct packaging reduces white rust, paint scratches, coil collapse, and claims after long-distance shipment. | Packaging specification, loading photos, weight list, shipping documents, and cargo-insurance terms. |
| 10 | Quality Assurance and Technical Support | Traceability, complaint handling, technical communication, inspection access, and corrective-action process. | Prefer suppliers with documented quality procedures, batch traceability, clear acceptance criteria, and defined response times. | Strong after-sales support helps resolve coating, dimensional, delivery, and application issues quickly. | Quality manual, traceability sample, inspection certificate, corrective-action template, and warranty terms. |
