Railway systems operate under some of the most demanding environmental and mechanical conditions. From passenger trains, metro rail and high-speed rail to freight trains and conventional railway infrastructure, metal components face rain, humidity, temperature changes, vibration, pollutants and, in coastal regions, saline environments. Over time, these conditions can accelerate corrosion of railway fasteners and other exposed steel components.
GEOMET® zinc flake coating provides an advanced solution for railway corrosion protection. This water-based, chrome-free zinc aluminium flake coating combines high corrosion resistance with a thin film, controlled friction characteristics and a non-electrolytic application process—important characteristics for high-strength railway fasteners.
What Is GEOMET® Zinc Flake Coating?
GEOMET® is an advanced zinc flake coating technology based on overlapping zinc and aluminium flakes in a binder matrix. Unlike conventional electrolytic zinc plating, the GEOMET® zinc flake coating process is non-electrolytic.
The zinc-rich coating provides cathodic or sacrificial corrosion protection, while the overlapping zinc and aluminium flakes create a barrier that reduces the penetration of moisture, oxygen and other corrosive agents.
The result is a thin yet highly corrosion-resistant coating suitable for fasteners and other precision metal components.
GEOMET® systems can provide a low film thickness in the 6–15 µm range, depending on the product and specification, while certain systems can deliver up to 2,000 hours of neutral salt spray performance under specified test conditions.
Why Railway Fasteners Need Advanced Corrosion Protection
Railway fasteners perform a critical role despite their relatively small size. Bolts, nuts, screws, studs, washers, pins and clips can be exposed to repeated vibration, mechanical loads and changing environmental conditions.
Corrosion can gradually attack an unprotected metal surface, potentially increasing maintenance requirements and making fasteners more difficult to inspect, remove or replace.
A high-performance anti-corrosion coating for railway fasteners therefore contributes to longer component life and more predictable maintenance.
Zinc flake coatings are particularly relevant here. ISO 10683 covers non-electrolytically applied zinc flake coating systems for steel fasteners including bolts, screws, studs, nuts, washers, pins and clips. The standard specifically notes their use for high-strength fasteners where internal hydrogen embrittlement is a concern.
How Is GEOMET® Coating Used in the Railway Industry?
Potential railway applications for zinc flake corrosion protection include:
- Railway bolts and nuts
- High-strength railway fasteners
- Bogie fasteners and bolted joints
- Rail fastening hardware
- Spring steel rail clips
- Screws, studs and washers
- Pins and clamps
- Suspension-related fasteners
- Underframe fastening hardware
- Structural fastening components
- Selected brake-related fasteners and hardware
A practical real-world example is the spring steel rail clip used to maintain clamping force between the rail and fastening system. Commercial railway fastening specifications demonstrate zinc flake coating as a corrosion-protection option for spring steel clips used in conventional railways, metro systems, heavy-haul rail and high-speed track systems.
Another practical example is rolling-stock bogie bolting. Bogies contain numerous bolted and high-load assemblies operating under vibration and outdoor exposure, making corrosion resistance, dimensional control and reliable fastening behaviour important engineering considerations.
How Does the Zinc Flake Coating Process Work?
GEOMET® coating begins with appropriate surface preparation of the metal component. The zinc aluminium flake coating is then applied using a suitable non-electrolytic method. Depending on part geometry and production requirements, zinc flake technology can use processes such as dip-spin, rack dip-spin or spray application.
During dip-spin processing, components are immersed in the coating material. Excess material is removed through spinning, helping create a thin and uniform layer.
The components are subsequently cured. Multiple coating and curing stages may be used to achieve the specified corrosion protection. Suitable topcoats can also be added where requirements include enhanced corrosion protection, specific appearance, chemical resistance or a defined coefficient of friction.
GEOMET® and Hydrogen Embrittlement Prevention
One of the biggest advantages of GEOMET® for high-strength railway fasteners is its non-electrolytic application.
Hydrogen embrittlement can occur when hydrogen enters susceptible high-strength steel and contributes to delayed cracking under stress. Certain manufacturing and surface-treatment operations can introduce hydrogen, making hydrogen embrittlement prevention an important consideration for safety-critical fasteners.
Because GEOMET® is applied through a non-electrolytic zinc flake coating process, hydrogen is not generated through an electrolytic deposition step.
This makes zinc flake technology particularly attractive for high-strength and high-tensile fasteners. ISO 10683 specifically identifies zinc flake coating systems as especially used for high-strength fasteners of 1,000 MPa and above to avoid the risk of internal hydrogen embrittlement associated with coating processing.
High Corrosion and Salt Spray Resistance
Railway equipment may remain outdoors for years while experiencing rain, moisture, humidity and industrial or coastal atmospheric exposure.
GEOMET® provides both barrier protection and sacrificial corrosion protection. Zinc preferentially protects the underlying steel, while overlapping zinc and aluminium flakes form a dense protective structure.
Depending on the selected GEOMET® system and specification, corrosion resistance can reach 720–2,000 hours in neutral salt spray testing according to ISO 9227. Actual performance depends on the coating system, thickness, substrate, geometry, topcoat and test specification.
This high salt spray resistance makes zinc flake technology valuable for railway components operating in demanding environments.
Thin Film Protection for Precision Railway Components
Another major GEOMET® coating benefit is high corrosion protection at relatively low coating thickness.
GEOMET® systems can operate around 6–15 microns, depending on the product and required performance.
This is particularly valuable for threaded railway fasteners, where excessive coating build-up can interfere with dimensional tolerances, thread engagement and assembly.
A thin zinc aluminium flake coating helps combine corrosion protection with dimensional precision.
Controlled Friction for Railway Bolted Assemblies
For a railway bolt, corrosion resistance alone is not enough. Fastener friction influences the relationship between tightening torque and resulting clamp load.
GEOMET® systems can be combined with specially engineered topcoats to provide a controlled coefficient of friction, supporting more predictable torque-tension behaviour.
For example, GEOMET® 500 combines corrosion protection with a controlled coefficient-of-friction range of approximately 0.12–0.18 according to ISO 16047.
This characteristic can be valuable in engineered bolted assemblies subjected to vibration, repeated mechanical loading and demanding installation specifications.
Key Benefits of GEOMET® Zinc Flake Coating for Railways
GEOMET® offers railway component and fastener manufacturers a combination of high corrosion resistance, thin coating thickness, cathodic protection, barrier protection, controlled friction and non-electrolytic processing.
Additional advantages include a water-based, chrome-free coating technology, strong performance in humid and saline environments, compatibility with high-strength steel fasteners and reduced coating-induced hydrogen embrittlement risk.
Longer corrosion protection can also contribute to extended component service life, fewer corrosion-related replacements, reduced maintenance requirements and lower lifecycle costs.
GEOMET® Zinc Flake Coating Technology from Growel
Growel brings GEOMET® zinc flake coating technology to Indian manufacturers through its collaboration with the technology developer. Growel provides GEOMET® chemistry and technical know-how for manufacturers seeking advanced zinc flake corrosion protection for fasteners and industrial components.
For railway fastener manufacturers, railway component suppliers and engineering companies, GEOMET® offers an advanced approach to protecting critical steel components without relying on thick protective layers.
From railway fasteners, bolts, nuts, screws and washers to clips, pins and selected bogie fastening components, zinc flake coating technology can help address the combined challenges of corrosion, precision, friction and high-strength steel.
For modern railways, metro systems, freight rail and rolling stock, that means more than rust prevention—it means engineering corrosion protection around the long-term reliability of the component.
FAQs
1. How can I contact Growel for GEOMET® Zinc Flake Coating requirements for railway applications?
You can contact us directly at corporatecommunications@growel.com. Our team will assist you with GEOMET® Zinc Flake Coating requirements for railway fasteners, bolts, nuts, clips, high-strength components and other suitable railway applications, along with technical or product-related queries.
2. Is there an inquiry form for GEOMET® Zinc Flake Coating requirements?
Yes. Please visit our GEOMET® Zinc Flake Coating Solutions page and scroll to the bottom, where you’ll find a simple inquiry form. Fill in your requirements, and our team will contact you to discuss GEOMET® coating technology for railway fasteners and suitable railway components.
3. Is there a support email for GEOMET® coating technical queries?
Yes. For questions about GEOMET® Zinc Flake Coating for railway applications, corrosion protection, railway fasteners, coating specifications or technical requirements, please email corporatecommunications@growel.com. Our team will assist you with your query.