Steel and Preservation

Steel is an alloy consisting of iron and carbon. Iron has been used for all sorts of purposes for more than 4000 years. Steel is exceedingly strong compared to other (light) metals. The production of steel requires relatively little energy. Steel is 100% reusable, making it fully compliant with the cradle-to-cradle policy Steel also has highly advantageous properties in respect of metal-fatigue. It is insensitive to galvanic corrosion and is highly suitable for welding.

A thermally galvanised column is guaranteed to stand for at least 40 years without maintenance. A well preserved column has a virtually limitless life span. Steel columns are less vulnerable to collisions and can be formed and shaped in an almost infinite variety of ways. All of the aforesaid properties speak in favour of the use of steel. In addition to the many advantages stated above, steel has a very attractive price tag.­


A steel column lasts a lifetime. Should the column eventually become redundant or be replaced by a new one under a renovation programme, then the steel can simply be recycled. The steel is then separated from all other waste products. By melting it, the steel is prepared for use in a new generation of columns. And the beauty of it is that no degeneration occurs. The recycled material retains each of its original properties. Steel is the most recycled material on the planet. Steel remains the best possible choice in terms of material. Steel is not consumed, it is used!



The majority of our columns are manufactured from steel. Steel has the characteristic that it must be protected against air oxygen, salt and moisture. In order for a steel object to be used sustainably, it must be treated for preservation accordingly. If it is not treated, then nature will eventually claim the object and return it to its original form: iron rust.

There are numerous ways of preserving a steel object. This page describes the most common preservation methods: thermic galvanisation, wet coating and powder coating. It also describes the methods for treating ground segments, something that is frequently done by our organisation.

In 1742, the French chemist Malouin discovered that it was possible to protect steel against air oxygen, salt and moisture by submerging it in molten zinc. With this discovery, the galvanisation process was born. In 1836, an economically viable staining procedure for steel components was developed by Sorel, which finally made it possible to thermally galvanise steel on an industrial scale.

verzinkprocesThe entire process of thermal galvanisation is described in the EN-ISO 1461 standard (formerly NEN 1275). Prior to submerging an object in a hot zinc plating solution (450°C), the object is degreased, stained and fluxed (see the process described above).

Thermal galvanisation has two major advantages in respect of other preservation methods:
1. full submersion, due to which the entire steel surface is coated with a layer of zinc (therefore also the inside of a column and all vulnerable components surrounding an assembly hatch);
2. zinc amalgamates with steel, thus creating an inseparable layer. If the zinc surface is damaged, then the cathodic effect prevents the object from corroding.


Thermal galvanisation is a physical process, in which the composition of the material (phosphoric and siliceous levels) and the thickness of the material are determinative in acquiring the required zinc layer thickness. The EN ISO 1461 standard specifies the minimum and average thicknesses for zinc for the various steel gauges. For more information, please refer to this standard sheet.


If a sealed wet coating is applied to a steel object, then the requirement for the steel surface of the object to be protected against air oxygen, salt and moisture is met. No corrosion will occur to the object as long as its steel surfaces are protected. There are currently 1001 different types of wet coatings and wet coating systems available and just as many different (RAL) colours; we suggest the advice of an expert in this area for reliable recommendations on the proper wet coating system. For the technical specifications of wet coating systems, please refer to the websites of Zandleven Coatings or International Coatings.

A sealing layer can also be obtained by applying a powder coating, in which an electrical charge is used to adhere the powder to the intended steel surface. The steel is then heated to 180°C in a furnace, as a result of which the powder adheres to the surface. The powder ultimately hardens into a high-quality protective layer. Powder coating (also: polyester coating or thermal paint) has a higher resistance to mechanical stress. Powder coating forms a smooth surface area, due to which it is not only easy to clean, but also has a timeless appearance. A disadvantage of powder coating becomes apparent when retouching is required: this requires careful preliminary treatment.

A duplex system is used to first thermally galvanise an object and then apply a wet or powder coating system. We often advise a duplex system for the treatment of steel columns, which prevents the formation of rust (thanks to thermal galvanisation) and creates a very attractive product (thanks to a wet or powder coating in any conceivable colour). The application of a wet or powder coating alone is not enough to provide full protection against the formation of rust in some vulnerable areas. Examples in this respect are door fringes, drill holes and cavities (see photograph below).



Each column segment close to the ground surface is vulnerable, seeing that it is exposed to (animal) urine, lawn mowers, wood cutters, salt, fluctuating ground water levels, etc. In order to prevent damage to your columns, we recommend additional ground segment treatment, for which we offer the following options:
– tar-free bitumen
– GPP ground level protection (glass fibre-reinforced plastic)
– asphaltic jute bandage
– heat shrinking sleeve
– steel cuff
– separate ground level protection, fitted after construction


Each material has its advantages and disadvantages. We shall be happy to advise you on what is best in your situation!


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