What are common quality risks when sourcing rebar and roofing sheets from China?

**Rebar (deformed steel bar):** - **Theoretical vs. actual weight.** Some mills produce "light-section" rebar that is dimensionally close to spec but under nominal weight, so a 12mm bar might weigh ~0.85 kg/m instead of the standard 0.888 kg/m. Buyers pay by quoted weight but receive less steel. - **Wrong grade.** A mill may quote Gr60 / B500B / Fe500 and ship Gr40 / B400 material. Mitigation: require MTC per heat, plus a third-party tensile/yield test. - **Surface rust beyond spec.** Light surface rust is acceptable per most standards; heavy flaking is not. - **Bundle weight variation.** Bundles should be tied and within ±2% of stated weight. **Galvanised / pre-painted roofing sheets:** - **Coating mass below spec.** Sheets marketed as Z120 (120 g/m²) may test at Z80 or lower. Require coating-thickness testing during PSI. - **Base metal thickness shortfall.** A "0.4mm" sheet may measure 0.32-0.35mm. Use a micrometer at 10+ random points. - **Paint adhesion failure.** Pre-painted sheets should pass a cross-hatch tape test. - **Profile dimensions and pitch.** Profile depth and rib pitch outside spec means sheets won't interlock or fit purlins. **General mitigations:** 1. Specify the exact standard in the PO (GB, ASTM, EN, JIS) 2. Mandatory MTC per heat/coil 3. Pre-shipment inspection by a third-party agency 4. Holding back 10-20% payment until clearance/inspection See related: [Steel products](/products/steel) and [Roofing materials](/products/building-materials).