GEOMET ®: Thin-film corrosion protection by BENSELER


In the area of surface technology, the thin-film corrosion protection process with the product GEOMET ® is the most widely used water-based process.
Find out more about the advantages and services in the field of thin-film technology with GEOMET ® below.

What is GEOMET ®?

GEOMET ® 321 is a patented technology consisting of passivated zinc and aluminum flakes in a binder. It was developed to meet the highest industrial requirements and regulations with regard to the environment, health and safety.

The corrosion protection system is applied by using various application techniques. This process is an environmentally friendly option for coating of smaller metal parts, as it offers very high corrosion protection with comparatively low layer thicknesses.

These layers can be combined with topcoats to achieve customized solutions in terms of functional properties, friction behavior and corrosion resistance of the system.

The characteristics of surface technology with GEOMET ® are:

  • Layer thicknesses usually 5-20µm on average, depending on requirements
  • Salt spray test DIN EN ISO 9227 NSS well over 1500 hours possible
  • Alternating test according to DIN 50017 KK/FKW/KWT at least 480 hours
  • No risk of hydrogen embrittlement
  • Metallic silver-grey
  • Can be painted with conventional paints and/or by cathodic dip coating
  • High resistance to diesel and gasoline, engine oils, organic solvents, coolants and brake fluids
  • In combination with different topcoats, the characteristics of the coating system can be adapted to specific requirements, making colored or black coatings possible
  • Fulfills worldwide specifications of the automotive industry

Application process with GEOMET®:

In principle, GEOMET ® coatings are produced by applying the liquid medium to pre-treated parts with final drying. The coating can be applied using bulk, spray or rack technology.

Process bulk goods dip-spin technology:

In the BENSELER large-scale production systems, the components are fed in automatically via dosing systems. They then undergo alkaline pre-treatment and, if necessary, are also blasted, depending on the delivery condition. They are then transferred to the coating process in an interlinked processing batch.

The batch is immersed in the liquid GEOMET ® and spun off using defined programs. This is followed by drying and baking of the first basecoat layer. Depending on customer requirements, this process is repeated several times. The GEOMET ® coating system is water-based and extremely low in solvents. At the end of this process, it forms a hardened, predominantly metallic layer that is bonded to the component.

Finally, the components are usually coated with a topcoat to optimize specific characteristics. In the case of threaded parts, the focus is often on the screw fastening features. Black topcoats are also possible.

At the end, the parts are filled from the system into the labeled customer containers according to the order. Before being made available in the finished goods warehouse, BENSELER undertakes a documented quality inspection and approval process.

Requirements for an application on bulk material with GEOMET ®:

In order to be able to apply the GEOMET ® thin-film corrosion protection process to bulk material, the components should:

• have a rotationally symmetrical shape
• be non-interlocking
• have a weight of less than 300 g/part
• or alternatively be pourable

view into geomet production site
GEOMET production line

Process for rack goods with the dip-spin technique:

At BENSELER, the coating for rack goods is applied to all parts that are no longer pourable, without any mechanical impairment of the functional characteristics of the parts.

This process technology can be used, for example, to coat rotationally symmetrical part geometries in the inner diameter or also undercuts that are given by design.
Coating with basecoat and topcoat is carried out in a large-scale production lines using base frames that are loaded with the parts.

The BENSELER specialists define the pre-treatment, which corresponds to a multi-stage alkaline hot degreasing process with rinsing and final drying, based on the evaluation of the condition of the raw material as it is delivered. If necessary, this can be supplemented by a further intensified pre-treatment process using blasting and subsequent dedusting.

Due to the larger part geometries and weights, extremely gentle pre-treatment handling of the parts in the processes takes place.

After the pre-treatment process, the parts are loaded onto rack levels, which are flexibly inserted into a cylindrical base frame.

The coating in the water-based medium is applied by immersing the entire frame in the paint system, which wets the parts. BENSELER removes the excess material down to the smallest droplets from the component by subsequent dripping and a defined spinning process.

In the subsequent oven, the parts are pre-dried on the rack and baked at a specified baking temperature and duration.

The coating process is repeated at least once more in the same way, depending on the corrosion resistance requirements.

After the cooling process, the parts are coated with a basecoat layer of the paint system. This is cross-linked with the base metal.

To complete the surface, a topcoat is usually applied to create a sealing effect and set specific characteristics.

For example, friction value windows can be set for threaded parts or a colored final finish can be created.

The same coating technique for the parts on the rack applies to the topcoat: dipping, spinning, drying and cooling.

Finally, the parts are removed from the racks according to the order, packed into the labeled customer containers and subjected to a documented quality inspection and approval process before being made available in the finished goods warehouse.

Process for rack goods using electrostatic spraying technology:

BENSELER uses electrostatic spraying technology to coat rack goods for all parts that are not pourable. This process does not mechanically impair the functional characteristics of the part.

The coating is applied by using frames fitted with steel parts, which pass through a spray booth where they are painted using electrostatic technology.

A typical example of the use of spray technology is the partial coating or coating of masked parts where corrosion protection is only required for certain areas of the part surface.

The pre-treatment is always defined on the basis of the evaluation of the delivery condition. After a multi-stage alkaline hot degreasing process with rinsing and final drying, a further pre-treatment process is carried out using blasting and subsequent dedusting if required.

Due to the larger part geometries and weights, the specialists at BENSELER handle the components with extreme care in the individual pre-treatment processes.

After pre-treatment, the parts are loaded onto customized cross beams, which are attached to a base frame and transported via a power-and-free conveyor.

Coating is carried out in a spray booth using paint-saving, electrostatically supported high-speed rotary bells in several cycles, each with an intermediate drying process.

In the subsequent oven, the parts are baked on the rack at a specified baking temperature and duration.

To complete the surface, a topcoat is usually applied, which enables the same sealing effect and the same specific characteristics to be set as with the rack material using dip-spin technology.

The same coating technique for the parts on the frame applies to the topcoat: Spraying, drying and cooling.

At the end, the parts are removed from the racks according to the order and packed into the marked customer containers. Before being made available in the finished goods warehouse, BENSELER subjects the components to a documented quality inspection and approval process.

Requirements for an application with spray or rack technology using GEOMET®:

The coating options for GEOMET ® coating with spray or rack technology are very diverse. The specialists at BENSELER therefore check the suitability for your specific application on a part-specific basis.

BENSELER uses the GEOMET® 321 and GEOMET® 500 systems

GEOMET ® 321 is the most frequently used product in zinc flake coating and is used for the corrosion protection of fasteners and for a wide variety of metal components. It can be combined with the PLUS® or DACROLUB® topcoats to achieve an individual coefficient of friction.

GEOMET ® 321, especially with the topcoat PLUS VLh, is the system most frequently specified in the German automotive industry. Its main advantage is the good coverage of the bolting requirements according to the VDA recommendations.

GEOMET ® 500 is a system with integrated lubrication that is suitable for many applications without the need of a topcoat.

Here is an overview of the advantages of the GEOMET ® product family:

  • GEOMET ® coating products meet automotive industry specifications worldwide
  • GEOMET ® coating products are REACH compliant and fulfill the EU End-of-Life Vehicle Regulation 2000/53
  • GEOMET ® coating products offer high corrosion protection from 600h to >1500h according to DIN EN ISO 9227 at low coating thicknesses of 5-25µm
  • GEOMET ® coating products have a permanent temperature resistance of 200°C with corrosion protection at the same time
  • There is no infiltration of the coating by corrosion, in contrast to paint coatings
  • The setting of defined friction coefficient windows leads to very good screw fastening features of threaded parts, even with multiple screw connections
  • No risk of hydrogen embrittlement as the coating is not applied electrolytically
  • The lower hardness of the zinc flake layer compared to electroplated zinc layers can be an advantage for subsequent assembly processes be an advantage
  • Good chemical resistance to organic solvents for example organic solvents, oils,
  • greases and brake fluids

Additional customer services for GEOMET ®

In addition to zinc flake coatings with GEOMET ®, BENSELER offers you the following customer services:

• Thread-locking coating of screws and nuts
• Individual testing and packaging
• 100% sorting by measurement
• Packaging assembly and labeling for the end customer
• Direct delivery to the end customer or consignment warehouse

Further special services are available upon customer request!


BENSELER technical information for zinc flake coating using GEOMET ®

To make sure that the product is perfectly suited to your requirements, the BENSELER sales team will be happy to provide you with personal advice at any time.

These BENSELER locations offer this procedure:

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