Hot-Dip Galvanized Steel

Hot-Dip Galvanized Steel

Hot-dip galvanized according to EN ISO 1461

For hot-dip galvanizing steel as the basic material is dipped into a zinc bath (about 450°C ≈ 842°F). After draining a more or less thin zinc layer remains as a coating. This layer forms an active as well as a passive corrosion protection: The thin layer protects the basic metal against humidity (passive) and also works as a sacrificial anode (active). The steel under the zinc layer is protected against corrosion as long as there still is zinc that has not yet been corroding. In the fresh condition the zinc layer is shining brightly. As time goes by a patina develops as a result of this corrosion which makes it appear darker and matter.

The main effect of hot-dip galvanizing is to protect the objects against corroding. By the way of hot-dip galvanizing a cost-effective lifelong but only technical surface is achieved. Requirements concerning the look of the surface are not defined. In order to avoid customer complaints we therefore recommend considering alternative or additional color-coating.

Feuerverzinkte Bank - Typ LEIPZIG

Hot-dip galvanized bench, type LEIPZIG, with seat rest made from 100% hardwood and side rests

Layer Thickness

All our hot-dip galvanized metal garden objects are treated according to the standards of the DIN EN ISO 1461. This guarantees a coating thickness of 55 μm with a material thickness between 3 and 6 mm, and a coating thickness of 70 μm with a material thickness of more than 6 mm. Thanks to this thickness – depending on the environmental conditions – the passive and active protective effect of the zinc layer can have a lifespan of more than 50 years.

Zinc-coating with Patina

In fresh condition the zinc layer is shining brightly. As time goes by a patina develops. As a result of this corrosion the surface appears darker and matter. Hot-dip galvanized objects can be color-coated. To make sure that the color sticks to the hot-dip galvanized surface, the surface usually has to be prepared by using an appropriate adhesive primer. If the adhesive primer was really used on the whole surface often only shows after years. On the basis of our experience we recommend to manufacture all garden objects from stainless steel (V2A) and then color-coat them. This is not the cheapest variant, but then you will be sure to enjoy your color-coated garden objects for a lifetime.

White Rust with Hot-Dip Galvanizing

Basically the white rust problem can appear with all hot-dip galvanized objects! White rust is the name for corrosion forms of the hot-dip galvanized surface. The white rust is not wanted, as it looks shabby, but it does not have any effect on the corrosion protection. White rust can develop, when the freshly zinced objects are stored under unsuitable weathering conditions, i.e. temporary air exclusion and simultaneous water contact, above all condensed water which is poor in minerals. Low temperatures especially under the dew point reinforce that effect.
The classical case: In fall and winter the objects are waiting to be installed, covered with a foil. The white rust can develop within a few hours.
In order to reduce the development of white rust some companies in the galvanizing industry offer additional protective layers. These are relatively expensive and above all useless if the freshly zinc-galvanized objects are treated and stored appropriately. That is why an additional protective coating is no standard and has to be agreed on and ordered separately.

The white rust can be removed under certain circumstances. But it has to be remembered: The earlier, the better.

White rust can be removed mechanically by using hard nylon brushes. The treated surfaces have to be rinsed with lots of water. Wire brushes are not suitable, as they leave scratches in the soft zinc coating.

Weißrostbildung auf der Oberfläche an einer Sitzbank

Development of white rust on the surface of a bench

Reducing or Removing White Rust

In order to reduce the development of white rust some companies in the galvanizing industry offer additional protective layers. These are relatively expensive and above all useless if the freshly zinc-galvanized objects are treated and stored appropriately. That is why an additional protective coating is no standard and has to be agreed on and ordered separately.

The white rust can be removed under certain circumstances. But it has to be remembered: The earlier, the better.
Under certain circumstances white rust can be removed mechanically by using hard nylon brushes. The treated surfaces have to be rinsed with lots of water. Wire brushes are not suitable, as they leave scratches in the soft zinc coating.

Conserving Natural Resources and Ecologically Sustainable

Corrosion protection by the way of hot-dip galvanizing saves recources and is sustainable. In direct comparison with other procedures a big amount of CO2 is saved.

Suggestion for Tender Template

Note: In order to have the best possible protection against white rust we recommend an additional seal directly at the plant of the company that does the galvanizing part. This is an extra service compared to the regulation DIN EN ISO 1461 and has to be agreed on and ordered separately. Text suggestion: “With additional protective coating for further protection against white rust after the hot-dip galvanizing process.”