Processes » Galvanizing
Galvanizing (zinc thermal diffusion)
Zinc thermal diffusion is the most advanced technology to galvanize parts. It creates a new quality, which is significantly better than any previously known galvanizing method. Galvanizing is done in enclosed chambers in which the process of zinc thermal diffusion runs into the metallic structures of iron.
With the application of the gas phase – different to the immersion method for hot-dip galvanizing or lamella – even cavities of durable layers are reached. High strength zinc layers are already achieved around the 20 µm mark, which in traditional methods could only be obtained with more than 50 µm. Advantages of the precise dimensions and greatly reduced setting behaviour were largely achieved by ageing the parts.
Some of the zinc thermal diffusion benefits are:
- Strong adhesive connection of the layer – without peeling and cracks
- High quality of the coating – period of corrosion resistance is about two times longer than for hot-dip galvanizing
- Very high wear resistance
- Uniform thickness of the obtained layer
- Smooth coating which eliminates the zinc skin formation and roughness
- Perfect as an undercoat before painting and vulcanization
- Variable thickness of the galvanized coating of 15 µm up to 120 µm
- A relatively low process temperature – treatment option of special parts and strength of the steel alloy
- Environmentally friendly process, without chromate coating
- Very good protection of threaded elements
- No hydrogen brittling of components
In combination with CDP coating or other wet or powder paints, it is possible to create thus a highly corrosion-resistant surface in any colour as a duplex system.
A duplex system is as per EN ISO 12944-5 a corrosion protection system which consists of a galvanizing in combination with one or several of the following coatings.
Galvanizing and coating complement each other. Galvanizing is protected against atmospheric and chemical influences by the overlying coating. Thereby the service life of the galvanizing is increased. Conversely, damages to the coating have no adverse effects since the galvanizing can withstand higher loads due to its great durability and abrasion resistance. The rust creepage typical for coating cannot occur. The overall protection duration of a duplex system is 1.2 to 2.5 times longer than the sum of the relevant individual protection periods of galvanizing and coating thanks to the so-called synergism effect between galvanizing and coating.