Material selection for high-performance cylinders: corrosion protection and service life

Why does the right choice of material for hydraulic cylinders make such a decisive difference?

Because the choice of material and coating directly determines the service life, performance and total cost of the cylinder. If you choose a material that resists corrosion, minimises wear and tear and is precisely suited to the operating conditions,

• your unplanned downtime will be reduced to a minimum,

• maintenance and spare parts costs will be drastically reduced and

• the service life of the entire system will be extended many times over.

In short: an optimised choice of material for the components of the hydraulic cylinder transforms a potential wear and failure part into a corrosion-resistant hydraulic cylinder that works reliably for years and provenly increases the overall profitability of your plant.

Challenges in corrosive and abrasive operating environments

Offshore installations, mines and chemical parks subject hydraulic cylinders to extreme conditions, day and night, around the clock. Here we present three common operating environments:

• 1.

  Offshore technology

  Hydraulic cylinders used in offshore technology are exposed to extreme environmental conditions – salty spray, high humidity and strong UV radiation place materials under constant stress. They must therefore be protected with seawater-resistant coatings to reliably prevent corrosion, material embrittlement and loss of tightness. In addition, high-quality sealing systems and rust-free materials are crucial for a long service life in maritime applications.

• 2.

  Mining applications

  Hydraulic cylinders in mining must withstand extreme mechanical loads, abrasive particles and harsh environmental conditions. They are used in conveyor systems, drilling rigs or support systems and therefore require robust designs, wear-resistant coatings and reliable sealing systems. High operational reliability and long service life are crucial to avoid expensive downtime during operation.

• 3.

  Aggressive chemicals

  Hydraulic cylinders that come into contact with aggressive chemicals – for example, in the chemical or process industry – must be made of particularly resistant materials. Corrosion-resistant stainless steels, special sealing materials and chemical-resistant coatings protect the cylinder components from attack and material failure. Only through careful material selection and coordinated sealing can safe and long-lasting operation be guaranteed in such environments.

The following applies in all scenarios: Only a coordinated system consisting of a resistant base material and high-performance coating achieves the necessary dual effect of corrosion and wear resistance, thus transforming a potential weak point into a low-wear cylinder with maximum service life.

Base materials for cylinder housings and piston rods

From classic tempered steel to cast steel materials to stainless and duplex steels – the range of materials for high-performance cylinders is vast. In practice, however, these options can be reduced to three main groups, each of which scores differently in terms of strength, corrosion protection, wear resistance and cost.

• Quenched and tempered steels (Q&T steels)

  These classic materials offer high tensile strength and fatigue resistance at a moderate price. Hardening and tempering create a high-performance structure that reliably absorbs impact loads and bending moments. Their drawback remains their limited corrosion protection – which is why they are usually coated or nitrided to transform standard steel into a low-wear cylinder for medium environmental loads.

• Cast steel materials

  Cast steel materials are particularly suitable for geometrically complex cylinder bases or heads, where machining would be very costly. The casting process allows complex contours, connection shapes or internal structures to be produced economically. At the same time, cast steel components offer high strength and good weldability, making them ideal for demanding hydraulic applications.

• Stainless and duplex steels

  Austenitic stainless steels are resistant to seawater, but are softer and prone to cold welding (galling). Duplex steels combine austenitic toughness with ferritic strength; their high PREN value (> 34) protects them even in continuous contact with chlorides. Stainless steels offer excellent corrosion protection, but require more effort in processing and handling. Machining is more demanding, and the material costs are also significantly higher than those of conventional steels. Nevertheless, their durability and resistance make them worthwhile for use in corrosive applications.

The key question is always: Which material and coating package achieves the best cost-benefit ratio in your process and transforms the cylinder into a robust, low-wear, long-term solution that takes into account strength, corrosion and wear protection in equal measure?

Coatings & surface treatments for piston rods (corrosion protection)

The piston rod is constantly exposed to changing pressure, tensile and bending forces and is also in direct contact with media, dust and chemicals.

Depending on the requirements under which the piston rods are used, the appropriate choice of coating must be made with regard to its advantages and disadvantages. To ensure that it does not corrode or lose its dimensional stability due to material removal, even under demanding conditions, the piston rod needs a surface that is both chemically dense and mechanically hard. Nitriding, hard chrome plating, fusion bonded coatings and chemical nickel plating have proven particularly effective.

Hard chrome plating (Cr VI process)

Hard chrome plating is considered a cost-effective industry standard for surface finishing of piston rods. The applied chrome layer is typically 20–30 µm thick and achieves hardness values of 900–1,100 HV. A characteristic feature is the fine network of cracks in the chrome layer, which supports the even distribution of lubricants and thus reduces friction wear.

Subsequent finishing by grinding and polishing significantly improves the surface quality, reduces roughness and thus protects seals, resulting in a longer service life for the entire sealing system.

Even a single-layer chrome plating provides effective wear protection for the piston rod surface. However, this is not sufficient for applications in corrosive environments. In this case, a two-layer chrome plating is recommended, in which the crack networks of the two layers are offset from each other. This effectively limits the diffusion of corrosive media and significantly improves corrosion protection.

For the highest corrosion resistance requirements – especially in aggressive media or extreme environmental conditions – chemical nickel plating is the most effective alternative, despite its higher cost.

Chemical nickel plating

Nickel and chrome coatings offer effective protection against corrosion, primarily in aggressive environments such as the offshore or process industries. Chemically deposited nickel coatings are characterised by their uniform layer distribution, enabling a continuous, pore-free surface with high resistance to moisture and aggressive chemicals.

Duplex systems such as nickel-chromium or modified variants with lubricating additives further increase abrasion resistance and functional reliability. Compared to conventional coatings, however, this protection is associated with higher costs – both in terms of material usage and the coating process itself.

Service life and maintenance cycles – economic effects

An intelligent combination of suitable material and high-quality coating transforms the piston rod from a wear part into a durable and reliable component.

Thanks to greater wear and corrosion reserves, maintenance can be scheduled during low-production phases and combined with other work – lengthy troubleshooting in a mine or on an offshore platform often costs more than a premium cylinder itself.

The ecological footprint also improves: a longer service life reduces material and resource consumption, lowers lubricant requirements and reduces emissions through lower maintenance costs and less transport. In addition, smoother, low-wear cylinders reduce internal friction loss in the system, so that pumps consume less energy.

A corrosion-resistant hydraulic cylinder increases plant availability, reduces the costs of hydraulic cylinder maintenance and supports sustainability goals – added value that is noticeable both technically and economically.

Conclusion: This is what matters when choosing materials for hydraulic cylinders

Whether offshore, mining or chemical plants – only a precisely coordinated combination of base material and coating protects the hydraulic cylinder permanently against corrosion and wear. The right decision reduces your overall costs, minimises downtime and improves the CO₂ balance of the plant.

That's why you should rely on ACONA when it comes to well-founded hydraulic cylinder material selection, reliable corrosion protection and truly low-wear cylinders – so that performance and service life are just right.