Galvanization refers to the durable corrosion protection of steel and iron components by means of a zinc layer. In Darda GmbH’s fields of application—from concrete demolition through strip-out and cutting to rock excavation, tunnel construction, and natural stone extraction—attachments and power units operate under wet, dusty, and often chloride-laden conditions. There, appropriate galvanization protects against rust, reduces downtime, and supports reliable function of components such as bolts, hydraulic fittings, or sheet-metal housings on concrete demolition shears, rock and concrete splitters, steel shears, multi cutters, combination shears, tank cutters, stone splitting cylinders, and hydraulic Power units.
Definition: What is meant by galvanization
Galvanization is understood as the application of a zinc layer to steel or cast iron. Zinc protects in two ways: as a barrier against moisture and oxygen, and through cathodic protection, in which zinc preferentially corrodes and thus “sacrificially” also protects exposed steel areas. The protective effect depends on the process, coating thickness, alloy, surface preparation, and the respective environment. In the context of demolition and separation technology, galvanization mainly concerns small parts (bolts, nuts, washers), hydraulic components (fittings, adapters), covers and brackets, as well as occasionally larger steel components when these receive a zinc-based primer or topcoat in addition to paint.
Methods of galvanization: hot-dip galvanizing, electroplated galvanizing, and alternatives
In practice, several methods are used that differ in coating build, adhesion, edge coverage, temperature exposure, and cost-effectiveness. In the environment of Darda GmbH, depending on component size and load, hot-dip galvanized, electroplated, as well as zinc-flake or zinc–nickel–coated parts are typically installed.
Hot-dip galvanizing (batch galvanizing)
When cleaned steel parts are immersed in molten zinc, alloyed zinc–iron layers with high coating thickness and very good edge coverage are formed. Advantages include a robust barrier effect and long protection duration, especially in harsh, humid, and chloride-laden atmospheres—for example on demolition sites or in tunnel heading. For large, thick-walled components used with concrete demolition shears or rock and concrete splitters, hot-dip galvanizing offers a resilient base, often in combination with an additional coating (duplex system).
Electroplated galvanizing
Here, zinc is deposited electrolytically. This produces fine, uniform layers with a good appearance, suitable for precise fits and small parts. In demolition and cutting applications, electroplated bolts, nuts, and washers are common—often with subsequent passivation. At the same coating thickness, the protection duration is lower than with hot-dip galvanizing; however, it is suitable for interior areas or temporary outdoor use.
Zinc–nickel and zinc-flake
Zinc–nickel alloys significantly increase corrosion protection compared to pure zinc layers and are widespread on hydraulic fittings that, on hydraulic power units, steel shears, multi cutters, and concrete demolition shears, are frequently exposed to saline splash water and alkaline cement slurry. Zinc-flake systems (without electrolytic hydrogen introduction) are particularly suitable for high-strength fasteners, where the risk of hydrogen embrittlement should be minimized.
Strip galvanizing (continuous galvanizing)
Steel strip is galvanized before forming. The process delivers very uniform layers and is relevant for sheet metal, covers, or guards on equipment. In harsh environments, an additional coating or a duplex build is recommended.
Duplex systems
The combination of galvanization and coating (e.g., paint or powder coating) combines cathodic protection with a durable top layer. Especially for equipment in concrete demolition and specialized deconstruction, a duplex system increases service life and facilitates later repairs.
- Coating thickness and reserve: Hot-dip galvanizing offers high reserves; electroplated systems shine on precision parts; zinc–nickel excels on hydraulic connections.
- Edge coverage: Hot-dip galvanizing and zinc-flake generally perform better on sharp edges than thin electroplated layers.
- Repairability: Zinc-rich touch-up materials adhere well to hot-dip galvanized and blasted substrates.
Galvanized components on attachments and power units
In Darda GmbH’s application fields, galvanized parts can be found in many places. The following classification helps select suitable systems and realistically assess maintenance needs.
Hydraulic fittings and adapters
Hydraulic lines on concrete demolition shears, steel shears, multi cutters, combination shears, and rock and concrete splitters are pressure-loaded and frequently exposed to moisture, dirt, and chlorides. Zinc–nickel coatings provide robust corrosion resistance here, including on edges and internal threads. Suitable sealing systems and gentle installation are important to avoid damaging the coating.
Bolts, nuts, washers, and spring washers
Fasteners on housings, guards, brackets, and frames are often electroplated or protected with zinc-flake. For high-strength bolts, a coating without the risk of hydrogen uptake is advantageous. Regular re-tightening according to installation specifications preserves preload and reduces relative movements that abrade protective layers.
Covers, brackets, and guards
For sheet-metal parts, strip galvanizing and an additional paint build increase resistance to abrasion by concrete and rock dust. In impact-loaded areas (e.g., on concrete demolition shears), edges should be carefully radiused and coated so that the zinc layer does not thin prematurely.
Operating conditions: concrete demolition, tunnel construction, natural stone, and special applications
The choice of galvanization is based on medium, temperature, mechanical load, and cleaning regime. In Darda GmbH’s application areas, moisture, sand, dust, cement slurries, and chlorides primarily define the corrosion exposure.
Concrete demolition and specialized deconstruction
Moist, alkaline cement slurries and de-icing salts stress layers heavily. For exposed steel parts, hot-dip galvanizing or duplex systems offer long protection duration. Fasteners benefit from zinc–nickel or zinc-flake. In concrete demolition and special deconstruction contexts, impact and abrasion act on concrete demolition shears—regular cleaning removes abrasive dirt and preserves the zinc layer.
Strip-out and cutting
Indoors, condensation and dusts are decisive. Thinner electroplated layers can be sufficient, provided they are not damaged by tool contact. With tank cutters, high temperature gradients act on surrounding components; zinc layers should not be overheated continuously.
Rock excavation and tunnel construction
Humid air, splash water, and occasional chemical exposure are typical. Galvanized hydraulic fittings and coated housings resist these media well. Corrosion at contact points between dissimilar metals can be minimized by insulating interlayers and suitable material pairings.
Natural stone extraction
Heavy dust and abrasive sludge lead to mechanical removal. Regular rinsing followed by drying prevents underfilm areas and white rust formation.
Special applications
With long-term exposure to splash water or in industrial atmospheres, higher coating thicknesses and duplex systems are the first choice. For short-term, mobile operations, electroplated layers with suitable passivation can be economical.
Coating thickness, environment, and protection duration
The protection duration of a galvanization increases with coating thickness and suitable passivation, but depends strongly on the environment. In dry indoor spaces, thin layers last a long time; in salty, humid outdoor air, a thicker layer or a duplex build is recommended.
- Electroplated galvanizing: typically approx. 5–20 µm
- Hot-dip galvanizing (batch galvanizing): typically approx. 50–150 µm
- Zinc-flake systems: typically approx. 8–25 µm
- Zinc–nickel coatings: typically approx. 8–20 µm
In abrasive applications (e.g., at the jaw area of concrete demolition shears), mechanical wear dominates; there, the design should minimize exposed surfaces and ensure serviceability (replacement of wear parts).
Mechanical and thermal influences
Blows, edge contact, and friction can remove zinc layers locally. Cathodic protection bridges small defects, but larger damaged areas should be repaired. Thermal effects must be considered: Zinc layers lose performance at sustained temperatures well above 100–120 °C; when welding or thermally cutting galvanized components, suitable work procedures and ventilation are required. Before welding, zinc is usually removed in the seam area to avoid porosity; afterwards the surface is rebuilt in a corrosion-protection-compliant manner.
Maintenance, cleaning, and touch-up
Proper care extends the service life of galvanized components on Darda GmbH equipment.
- Regularly remove contaminants (cement slurries, dust, salt) with water and then dry.
- Use mild cleaning agents; avoid strongly acidic or chloride-containing cleaners.
- Repair small damages with zinc-rich touch-up materials. Clean the substrate, remove loose products, allow to dry, and coat according to the instructions.
- Check screw connections according to the maintenance plan; replace damaged parts to avoid crevice corrosion.
Duplex systems can be locally reworked well if adhesion and coating build are observed. Light edge rounding helps distribute the coating more evenly on edges.
Typical damage patterns and causes
White rust (zinc-containing, light products) forms during damp storage without air circulation; initially it is mostly visual, but over time it can weaken the protective layer. Red rust indicates areas that have corroded through and requires touch-up or part replacement. Galvanic corrosion can occur with unfavorable metal pairings; suitable separating layers and corrosion-resistant fasteners reduce the risk.
For high-strength bolts, hydrogen embrittlement is a noted issue. Coatings without electrolytic hydrogen introduction or subsequent heat treatments can reduce risks. In safety-relevant connections—such as on concrete demolition shears or rock and concrete splitters—approved coating systems with documented process control should be used.
Selection criteria for processes and coating systems
The suitable galvanization results from the interplay of component geometry, load, and desired protection duration. For large, widely exposed steel parts outdoors, hot-dip galvanizing, often combined with coating, has proven effective. For precise fasteners and hydraulic components, electroplated systems with high-quality passivation, zinc–nickel, or zinc-flake are advisable. In abrasive zones (e.g., at the working edge of concrete demolition shears), constructive wear protection with good service accessibility takes priority; galvanization protects the adjacent areas.
- Environment: dry indoors to humid, salty outdoors
- Mechanics: impact, abrasion, edge contact
- Temperature: proximity to cutting or separating areas
- Service: ease of cleaning and repair
- Compatibility: seals, tightening torques, fits
Galvanization, sustainability, and resource conservation
Zinc is widely recyclable, and long-lasting protection systems reduce resource consumption through less frequent part replacement. An appropriate choice of processes, combined with good care, improves the service life of components in Darda GmbH’s tough applications and helps save material and energy over the life cycle.