Hot-dip galvanise

Hot-dip galvanising offers excellent long-term protection against rust, even in hard-to-reach areas and in pipes, hollow sections and welded parts in general.

The surface is abrasion-resistant, impact-resistant and scratch-resistant, and even minor damage can be easily repaired with zinc dust paint.

Hot-dip galvanised components are almost maintenance-free and, depending on the environment, have a service life of 25 to 100 years. This has been confirmed by decades of experience in the respective areas of application (outdoor weathering) on site.

In the case of scratches and scuffs, cathodic protection comes into effect, which builds up a barrier by electro-chemical means and thus also protects damaged areas from corrosion.

Thanks to the metallurgical bond between the zinc layer and the steel material of the component during hot-dip galvanising, this method of galvanising provides optimum protection against so-called base corrosion.

The layer thickness (45-150 µm) depends on the thickness of the base material and is regulated by ISO 1461.

Over time, hot-dip galvanised surfaces undergo oxidation of the zinc surface, which causes the originally shiny, light-coloured surface to gradually turn dark grey. This is a natural oxidation of the zinc layer, which chemically stabilises and becomes more resistant as a result of this process. 

The alloy layer (zinc-iron) is hard and resistant to abrasion and impact.

• Ideal for building and construction components.

Damage to the zinc coating can be repaired within narrow limits in accordance with ISO 1461 – if necessary, it must be re-zinc-coated or repaired with zinc dust paint.
 

• Zinc is a natural, recyclable element.
• Galvanising plants operate without wastewater.
• Hot-dip galvanised products have a long service life and reduce maintenance costs.

The combination of long service life and low maintenance costs makes hot-dip galvanising an economically attractive solution in the long term, despite higher initial costs.

Immersion in the zinc bath (approx. 450°C) can cause deformation, especially in thin-walled or asymmetrical components.

The application of zinc causes tolerance changes, which can be problematic for precisely fitting components.

In the case of hollow bodies, sufficient ventilation and drainage openings must be ensured, which means that a design suitable for galvanising is necessary.

Otherwise, explosions may occur when the parts are immersed in the zinc bath, which can lead to the destruction of the component, personal injury, incomplete galvanising or damage to the plant technology.

The surface after hot-dip galvanising ranges from bright shiny to dark grey, depending on the silicon (Si) and phosphorus (P) content in the base material.

The oxygen in the ambient air gradually transforms the originally shiny, bright surface into a dark grey surface, which has no effect on corrosion resistance.

Since the surfaces are usually not smooth, zinc flowers, drips, roughness and slag inclusions may occur. These are permissible to a certain extent in accordance with ISO 1461 or must be reworked.

For visible components (e.g. in architecture), this is sometimes visually problematic, but permissible within ISO 1461.

Steels with a critical silicon or phosphorus content (Sandelin range and high silicon range) lead to excessive zinc coating or brittle zinc layers.
 

The entire component is galvanised – selective galvanisation of individual areas is not possible or only possible after manual preparation.

Threads, sliding surfaces or fits must be reworked or masked.

Welding galvanised surfaces requires special measures, as this produces welding fumes that are hazardous to health.

The powder coating of hot-dip galvanised components requires special surface treatment (sweeping).