Requirements for steel structures submitted for anti-corrosion coating
Products intended for hot-dip galvanizing must meet the following requirements:
Products must be made of steel in accordance with EN 10025; carbon content — no more than 0.24%, silicon — no more than 0.03% (or within 0.12–0.25%).
Depending on the chemical composition of the steel, the resulting zinc coating may differ in appearance (gloss, smoothness, thickness, etc.). Higher carbon and silicon content may worsen the visual appearance of the coating.
Galvanizing bath dimensions: 13000 × 1600 × 3200 mm.
Surface cleanliness must be no lower than class three.
Products must have technological openings for the free passage of zinc, located at opposite ends and as close as possible to weld seams.
Openings for hanging the products, or special holders, must be provided and positioned to prevent deformation under the product's own weight.
Products must not contain closed cavities; all elements must allow free access and drainage of liquids and molten zinc.
Pipes and nozzles must be open, without caps, so as not to obstruct the free flow of zinc.
Product surfaces must be cleaned of scale, burrs, paint, graphite, shavings, grease, welding slag, rust and other contaminants.
Structures must be welded butt-to-butt or with double-sided weld seams.
Welds of surface joints must be closed along the contour.
Welds must be uniform and continuous along their entire length.
Pores, cracks, slag inclusions and internal stresses are not allowed; all welds must be cleaned.
Products with residual internal stresses (after welding, stamping, rolling, etc.) may deform during galvanizing, so they must undergo stress-relief heat treatment before processing.
When joining elements of different thicknesses, the ratio of maximum to minimum thickness must not exceed 5:1 to avoid deformation at 440–450°C.
The metal supplier must be informed in advance that the products will be subjected to hot-dip galvanizing.
Loading and unloading of vehicles is performed using a crane and a forklift; manual unloading is not allowed.