Galvanized Flat Iron Bar Hot Rolled Gi Flat Steel for Construction Fabrication

Galvanized flat steel costs about RMB 800-1200/tonne more (galvanizing fee, depends on size and zinc requirements). But galvanized has 20-30 year anti-corrosion life, 3-5 times painted flat steel, lower lifecycle cost. Outdoor, humid, grounding corrosive environments must use galvanized; indoor dry environments can use regular flat steel with paint.

Welding damages zinc layer at weld area, after welding must: 1) Clean slag and spatter with wire brush or angle grinder; 2) Apply two coats zinc-rich primer (zinc >=92%, dry film >=60um); 3) Apply one coat galvanizing repair compound or silver paint. Repaired area corrosion performance should match overall zinc layer. Important grounding welds also need grounding resistance test.

Per GB 50057 "Building Lightning Protection Design Code", minimum galvanized flat steel section for lightning grounding: Class I buildings >=100mm2 (e.g., 40x4), Class II >=80mm2 (e.g., 40x3 or 25x4), Class III >=80mm2. Common sizes: grounding main 40x4mm, grounding branch 25x4mm, electrode connection 50x5mm.

Per GB/T 13912, steel thickness >=6mm: average zinc >=85um, local >=70um; thickness <6mm: average >=70um, local >=55um. Flat steel common thickness 3-10mm, generally requires average >=65um. We spot check with magnetic gauge at delivery, 5 points per member averaged, provide zinc thickness inspection report.

Stock sizes (40x4, 50x5, 25x4 etc.): 1 tonne MOQ, 3-7 days. Galvanizing required: 3 tonnes MOQ, 7-15 days (including 3-5 days galvanizing cycle). Large project orders can lock galvanizing capacity for batch delivery per schedule. We provide galvanizing + cut-to-length + drilling + bending one-stop fabrication service.