| Steel Substrate Grade | Common commercial, forming, and structural grades are selected according to required strength and forming performance. | The supplier should confirm the steel grade, yield strength, tensile strength, elongation, and intended application before production. | Mill test certificate, chemical composition, mechanical-property report, and product standard reference. | A mismatch between the ordered grade and delivered grade may cause cracking, deformation, or insufficient load performance. |
| Zinc Coating Mass | Common PPGI coating masses include approximately 80–275 g/m² total on both sides, depending on the product specification and corrosion requirement. | The order should state the coating designation or exact minimum coating mass, along with the test method and tolerance. | Coating-mass test report, agreed technical specification, and independent laboratory verification when required. | A lower-than-specified zinc layer can significantly reduce corrosion resistance and service life. |
| Organic Coating System | Polyester, silicone-modified polyester, high-durability polyester, and fluoropolymer systems are used for different durability and appearance requirements. | The supplier should identify the paint chemistry, primer, topcoat, back coat, and intended exposure environment. | Technical data sheet, coating-system description, paint batch information, and durability test results. | Selecting a standard coating for a marine, industrial, or high-UV environment may lead to premature fading or corrosion. |
| Paint Film Thickness | A common arrangement is approximately 15–25 μm on the top side and 5–10 μm on the reverse side, although specifications vary by coating system. | The supplier should guarantee the agreed nominal and minimum dry-film thickness for each side. | Dry-film thickness measurements at multiple coil positions and a coating inspection report. | Insufficient or uneven paint thickness can cause poor appearance, weak adhesion, and reduced weather resistance. |
| Base Metal Thickness | PPGI products are manufactured in various thicknesses, commonly from about 0.20 mm to 1.20 mm, subject to the production line and applicable standard. | Thickness should be specified as the ordered value, with clearly stated measuring location, tolerance, and whether the value includes metallic and paint coatings. | Micrometer readings, dimensional inspection report, and agreed tolerance standard. | Incorrect thickness may affect structural capacity, forming behavior, weight calculations, and compatibility with downstream equipment. |
| Coil Width and Dimensional Tolerance | Available widths commonly range from narrow slit coils to approximately 1,250–1,500 mm wide coils, depending on the line and order specification. | The supplier should confirm width, thickness, edge condition, camber, flatness, and applicable dimensional tolerances in writing. | Dimensional inspection report, coil photographs, and sample measurements before shipment. | Poor dimensional control can increase cutting waste and create feeding or installation problems. |
| Surface Finish and Color Consistency | Common finishes include smooth, matte, and textured surfaces; color consistency is normally assessed against an approved color sample or reference. | The supplier should provide a retained sample, agreed color reference, gloss requirement, and acceptable visual limits. | Color comparison record, gloss measurement, surface inspection report, and pre-shipment photographs. | Color variation between batches can affect the appearance of building facades, roofing, and visible panels. |
| Corrosion and Durability Performance | Durability depends on steel grade, metallic coating, paint system, film thickness, forming, installation, and exposure conditions. | The supplier should recommend a coating system based on UV exposure, humidity, pollutants, salt spray, temperature, and forming requirements. | Relevant accelerated-weathering, salt-spray, adhesion, and flexibility test results, where applicable. | A generic durability claim without exposure conditions or test details is difficult to validate. |
| Formability and Bend Performance | Bend performance varies with substrate grade, coating system, thickness, temperature, and bend radius. | The supplier should state the minimum recommended bend radius and confirm compatibility with roll-forming, stamping, or folding operations. | Bend test results, adhesion test, forming trial, and written processing guidance. | Excessive bending may damage the coating and expose the substrate to corrosion. |
| Quality Management and Traceability | Reliable production requires documented inspection, calibrated instruments, batch identification, and traceable raw materials. | Each coil should have a unique identification number linked to production records and test results. | Quality manual, inspection plan, calibration records, batch certificates, and nonconformance procedure. | Without traceability, it is difficult to identify affected coils or resolve quality disputes. |
| Packaging and Transportation Protection | PPGI coils require protection from moisture, impact, edge damage, condensation, and uncontrolled storage conditions. | Packaging should match the transport mode and include suitable wrapping, edge protection, strapping, labeling, and lifting instructions. | Packaging specification, loading photographs, packing list, and moisture or damage inspection at receipt. | Transit damage and wet-storage stains may occur even when the material itself meets the technical specification. |
| Order Flexibility and Supply Capacity | Minimum order quantities, available widths, production capacity, and lead times vary by specification and production schedule. | The supplier should confirm achievable quantity, production slot, delivery schedule, and contingency arrangements before accepting the order. | Written quotation, production schedule, capacity confirmation, and order-status updates. | Unclear capacity commitments can cause delayed projects, material substitutions, or partial deliveries. |
| Pre-Shipment Inspection and Claims Handling | Inspection may be performed by the supplier, buyer, or an independent inspection body according to the purchase agreement. | The contract should define acceptance criteria, sampling frequency, inspection timing, claim deadlines, replacement terms, and responsibility for verified defects. | Inspection and test plan, certificate of conformity, independent inspection report, and written warranty terms. | Vague acceptance and warranty conditions can make valid quality claims difficult to enforce. |
| Total Delivered Cost | The delivered cost includes material price, coating specification, slitting or cutting, packaging, inland transport, freight, insurance, duties, and inspection expenses. | Compare quotations on the same technical specification and delivery basis rather than using the lowest unit price alone. | Itemized quotation, delivery terms, freight estimate, duty information, and payment schedule. | A low initial price may conceal thinner coating, lower-grade substrate, higher waste, or additional logistics costs. |