Based on standards GOST 9.307-89 and STB ISO 14713-2-2012 requirements, materials to be exposed to hot-dip galvanizing must conform to the following criteria:
· Steel carbon content < 0,25%, silicon content < 0,37%, arsenic content <0,08%; please note that if silicon content in metal structures is more than 0,25% the appearance of the galvanized surface may worsen.
· Overall dimensions of metal structures to be galvanized - (length x width x height) are 14,5×1,6×3,2 m;
· Metal structures should be without airlocks, closed cavities and air pockets; all cavities must be accessible for unobstructed passing of liquids, molten zinc and flux decomposition gases in and out ; please note that at hot-dip galvanizing metal structures may shrink on exposure to high temperatures.
· Long-length articles (longer than 3 m) must have prearranged service holes at the edges. It is possible to weld loops on articles for hang-up;
· Containers, drums, coil pipes, threaded assemblies are galvanized by agreement with the customer;
· In case of vertical galvanizing pipes, fittings, boxes must have no plugs hindering free zinc flow out of internal opening;
· Drawings of components, including welded assemblies, should be agreed with the production plant. Customers provide certificates for metal used for the production of metal structures;
· Rolled-in scale, pin holes, burrs, inclusions (welding slag, molding compounds, mineral black, the marking dye, metal chips, lubricant residuals) on the surface of the parent metal are not allowed;
· Elements of metal structures must be butt-welded, or double-welded, or single-welded with backing welding.
· Butt-welded joints must be welded up along the outline;
· Joint welds must be even, tight and full through the full length (CO2 welding is desirable);
>Pin-holes, gas pockets, cracks, flux inclusions, welding couplings are not allowed (deseaming is obligatory, sandblast cleaning is desirable);
· Metal structures are to be delivered in batches classified by grades and profile. Structures shall be tagged; each tag must have indication of a steel mark;
· Coating thickness agreed with the customer must range from 40 microns depending on the steel type.