INHERENTLY GOOD:
STEP BY STEP FOR
HOT-DIP GALVANISING

Hot-dip galvanising in compliance with DIN EN ISO 1461: your components are in the best hands with us

The production process for hot-dip galvanising steel follows simple and sequential steps. The steel parts should have a bare metallic surface to achieve the best hot-dip galvanised finish.

We therefore ask our customers to take particular care to ensure that there are no foreign residues (e.g. residual paint coatings, weld slag, inscriptions, etc.) on the goods that are to be hot-dip galvanised as these could cause galvanising defects.

Technological requirements relating to "hot-dip galvanising-compatible design and production” also apply. This means, for example, that the steel parts have to be designed with inlet and vent apertures to allow air to escape from cavities and the zinc to flow in and out.

From bath to bath

To ensure comprehensive, efficient, durable and economical corrosion protection for your steel components, we take a systematic approach to hot-dip galvanising – from bath to bath and always with the utmost precision.

First, we pre-treat the steel parts in various wet-chemical baths. For this, they are subjected to a degreasing bath to remove any grease residues from the surface.

The degreasing agent residues are then washed off in the subsequent rinsing bath. This is followed by the pickling bath, in which diluted hydrochloric acid removes inherent residues on the steel parts such as rust and scale. As in soldering, substances are added in the flux bath. These provide for a final "fine cleaning" of the steel surface when it is immersed in the molten zinc.

This process also makes sure that the entire surface is evenly moistened during the galvanising process.

However, the aqueous flux film on the steel part is first dried onto the surface in a drying oven. The steel part is then finally galvanised in the zinc kettle.

The melting point of zinc is 419 °C, although on average the temperature of the liquid zinc in the zinc kettle is raised to 450 °C.

Hot-dip galvanising with one of the most state-of-the-art machines available today!

Thanks to the state-of-the-art machine technology, seamlessly interrelated processes and a highly motivated and qualified workforce, you benefit from:

fast delivery times
top quality
compliance with all environmental regulations

We achieve the maximum throughput capacity of 240 t/day with a kettle size of:

hot-dip galvanising shop (maximum working dimensions):
Length:	7000 mm	(Kettle: 7500 mm)
Width:	1320 mm	(Kettle: 1500 mm)
Depth:	2650 mm	(Kettle: 3350 mm)
Weight:	max. 2000 kg

BRISTA – environmentally aware action as the creed for a modern company

As an innovative company that is fully aware of its ecological responsibilities, we invest in the future – for the sake of humanity and the environment. With our state-of-the-art filter systems, high-tech control systems and ultra-precise testing equipment, we undercut all the required guidelines. This enables us to guarantee production processes that minimise energy consumption and waste.

Our galvanising machine meets not only today’s but also future requirements for eco-friendly, fast, cost-effective and competitive production methods.

It offers a clean working environment and emission-free workplaces as acid-contaminated areas are fully compartmentalised.
It operates with minimised energy consumption and waste. The emission thresholds stipulated by EU standards are undercut to a significant degree. We have all waste materials recycled at approved facilities.
Thanks to an intelligent heat recovery system, an energy utilisation rate of up to 96% is achieved.
We recycle rinsing water to prepare new baths.

Hot-dip galvanising protects against corrosion

Hot-dip galvanising gives your components sustainable and long-lasting protection against corrosion. Relevant standards for these various processing methods and typical applications are as follows:

Process	Standard	Application
Discontinuous hot-dip galvanising (batch galvanising)	DIN EN ISO 1461	Metalworking, metal construction and steel construction products e.g. gates, posts, twin wire mesh panels
Continuous hot-dip galvanising (strip galvanising – Sendzimir galvanising)	DIN EN 10143 DIN EN 10346	Hot-dip galvanised steel strip for automotive engineering, white goods (e.g. washing machines), fence construction (e.g. posts)
Continuous hot-dip galvanising (wire galvanising – Sendzimir galvanising)	DIN EN 10244-1 DIN EN 10244-2	Hot-dip galvanised steel wire for various applications e.g. gabions, twin wire mesh panels, hoardings

Discontinuous hot-dip galvanising (batch galvanising)
In this process, we galvanise previously manufactured steel parts (e.g. gates, twin wire mesh panels) completely, i.e. in one piece.

Continuous hot-dip galvanising (Sendzimir galvanising)
Sendzimir galvanising turns steel strips – coils, sheets or wire – into semi-finished products that are then processed further, e.g. posts for hoardings or twin wire mesh panels.

Differences between continuous and discontinuous hot-dip galvanising
The main difference between the two processes is the thickness of the zinc coating. While we achieve layer thicknesses of between 10 µm (72 g/m²) and 45 µm (324 g/m²) with Sendzimir galvanising, thicknesses of between 45 µm (324 g/m²) and well over 100 µm (720 g/m²) are obtained with batch galvanising depending on the thickness and composition of the steel.

Steel as the base material for BRISTA hot-dip galvanising: it’s the composition that counts

Steel as the base material has a huge influence in hot-dip galvanising. This applies above all to its chemical composition and in particular to its silicon and phosphorus content. These factors have a massive impact on the result of the ensuing zinc coating.

During hot-dip galvanising, a chemical reaction occurs between the steel and the molten zinc. If the chemical compositions differ significantly, considerable differences in the appearance and layer thickness of the zinc coatings and the surface structure can arise.

Appearance and surface properties: between look and functionality

DIN EN ISO 1461 emphasises that batch galvanising is primarily a process for protecting steel parts against corrosion. The focus is therefore on the protective effect and not on the appearance.

As the steel part is pulled out of the galvanising kettle, a flowery structured zinc surface is usually formed which is caused by lead and tin content in the zinc kettle.

The residual heat and composition of the steel cause the textured zinc surface to partially or fully take on a grey appearance. While this may not visually please everyone, it is definitely not a defect where corrosion protection is concerned. This also applies to the slow corrosion of every zinc coating over the course of time. Consequently the appearance can change from being lustrous to matt grey.

Hot-dip galvanising can also result in so-called zinc protrusions. These run-off points form when the material is pulled out of the zinc kettle. Excess zinc runs off at the lowest point of the material. When it hardens, zinc protrusions are formed. Production-related ash residues may also remain on the material.

Development of white rust

White rust is a powdery and water-soluble zinc corrosion product consisting of zinc hydroxide and zinc oxide, which develops in high-humidity environments on freshly galvanised parts at points where the grey zinc patina layer has not yet formed. The formation of white rust on hot-dip galvanised workpieces cannot be completely avoided. White rust is only an optical blemish, however, which washes off quickly when exposed to the weather and then allows the formation of the grey zinc patina as a protective layer.

The formation of white rust can be largely avoided by storing parts in dry rooms with sufficient ventilation. Covering parts with plastic film (e.g. as shrink-wrapped pallets), a frequently used measure, is not recommended as the non-drying condensation water stimulates the formation of white rust.

This has nothing to do with the galvanising process and is not a benchmark for its quality. Rather, it is a phenomenon that is largely dependent on the prevailing weather conditions during the storage or transportation of freshly hot-dip galvanised parts.

Zinc: protective effect thanks to corrosion resistance

Zinc is a relatively base metal and reacts fairly quickly with substances in its surrounding environment. Substances in the air therefore trigger a fast reaction with the metallic zinc causing zinc compounds (zinc oxides) to form on the surface. It is primarily these zinc compounds which give zinc its good resistance to corrosion.

The atmospheric effect on the zinc coating depends on the aggressive nature of the air. Clean country air is much less harmful to zinc than heavily polluted industrial air or particularly salty sea air.

Consequently, the durability of zinc coatings always depends on where the parts concerned are being used. Carbon dioxide (CO2), sulphur dioxide (SO2), nitrogen compounds (NOX) and hydrogen chloride (HCI) form compounds with metals. The most aggressive reactants among these are sulphur dioxide and hydrogen chloride, which have the greatest impact on the durability of corrosion protection systems.

Other factors such as dust, humidity and air temperature also have a detrimental effect on the zinc coating. The exposure to corrosion of the steel part can therefore vary greatly – depending above all on the ambient conditions in which it was installed. However, it is not possible to make a clear distinction between the different types of atmosphere (country, urban, sea and industrial air) as the transitions are fluid.

A very rough estimate of the corrosion load is provided by different corrosiveness classes derived from investigations:

Corrosiveness class	Atmosphere type	Corrosion load	Average zinc erosion
C 1	Indoor areas (dry)	negligible	< 0,1 µm / year
C 2	Indoor areas (occasional condensation // outdoor areas (country atmosphere)	low	0,1 - 0,7 µm / year
C 3	Indoor areas (high humidity, moderate air pollution) Outdoor areas (industrial or urban atmosphere or coastal climate with low chloride content)	moderate	0,7 - 2,1 µm / year
C 4	Indoor areas (swimming pools, chemical plants) Outdoor areas (industrial atmosphere, coastal climate with moderate chloride content)	high	2,1 - 4,2 µm / year

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