Packaging – tasks and properties
15.12.2021 | Article of Salzgitter Flachstahl GmbH
Packaging plays an important role for every product. The principal task of the packaging used for steel products is to protect them. And there are different kinds of packaging that are used for different products. Basic packaging is comprised of strapping band. In addition to which there are various elements that are used, such as rigid fiber components, edge protectors, strapping band underlays, all-round internal and external protection, foil wrapping or fiber-reinforced PE materials. Some steel products also need to be secured to suitable timber frames or wooden pallets to provide adequate protection during transport. Dependent on the destination specified by the recipient, for example, packaging suitable for shipment by sea, also known as export packaging, may be appropriate.
Besides protecting against damage, the main role of packaging is to protect against penetration by condensation. In the process of storage and logistics during manufacture, suitable climatic conditions are in place in the warehouses and storage areas to prevent condensation from forming. Once the product has left the works premises, by the nature of transportation, these conditions can no longer be maintained.
Notice 114 “Packaging, storage and transport” issued by the Steel Information Center states that “condensation can often occur unnoticed, in the interior of stacks or between the windings of a coil, where it is kept in place by capillary action, with the result that the effects of moisture can continue for an extended period without access to air. Condensate (sweating) occurs exclusively where damp, warm air cools on cold surfaces: warm air can absorb more moisture, that is to say, evaporated water, than cold air. Water contained in air that is warmer (than the surface of the steel) is therefore precipitated as condensate on the cold surface of the steel, for example in winter when packs of steel sheets or rings are brought from the unheated material storage area into the heated production area, where the moisture level is relatively high.” (Source: Notice 114, Packaging, storage and transport of uncoated and coated strip and sheet, 2010 edition, Steel Information Center).
Above all in the “cold season of the year”, Salzgitter Flachstahl recommends the use of winter packaging to provide suitable protection for steel products against the possible formation of wet storage stains. The tried and tested winter packaging preferred by Salzgitter Flachstahl is comprised of fiber reinforced, PE-coated sodium paper with integrated corrosion inhibitors (“VCI paper”). This packaging serves not only as a physical barrier, it also actively deters corrosion.
The metallic surface coatings applied during the strip galvanizing process consist of reactive zinc or zinc alloys which offer excellent protection against corrosion. With the application of oil or chemical passivation, these zinc surfaces can also be protected against corrosive effects when properly transported and stored. However, the protective effect of these measures is not sufficient to prevent localized corrosion damage due to condensing moisture. Therefore, whenever condensation cannot be excluded through other measures, it makes good sense to use transport packaging. In addition, it is particularly important that this packaging should not be removed at the point of destination until the coil is “acclimatized". Adaptation to the ambient temperature generally takes 3 – 4 days. For as long as moisture continues to condense on the packaging, the process is not yet complete.
In conclusion it may be said that, dependent on the actual specification, the optimum mix of post-treatment, packaging, transport and storage conditions should be selected in order to minimize the possible risk of the material deteriorating relative to the target standard required for subsequent processing. Consumers should keep in mind the potential physical-chemical conditions that may apply during transport, in order to choose the most ideally suitable packaging to meet their needs.
The logistics concepts and corresponding packaging types available from Salzgitter Flachstahl offer en extensive range of options.