Galvanic zinc plating

Processes

Galvanic zinc plating

Zinc protects more precious metals from corrosion and as such is indispensable in many industries. Galvanic zinc is deposited using acidic or alkaline electrolytes. The gloss level of the surface can be adjusted from matt to glossy by adding organic substances.

In contrast to other coatings, zinc also provides active cathodic corrosion protection in addition to its shielding effect. In contrast to the more precious iron, zinc acts as a sacrificial anode. This effect also protects the base material in case of damage after coating (scratches or impact marks). Additional properties are achieved by downstream processes, such as passivation, sealing and other similar processes. The modular Collinox coating systems are adapted to customer requirements.

Inquiry Technical data

Advantage

Advantages at a glance

Corrosion - Surface protects.
The natural state of metals is an oxide. In the metalworks the oxide is extracted by using oxygen and energy and the pure metal is obtained. However, the metal is “predestined” to return to its original state at exposure to oxygen and water. And the less precious the metal is, the faster it happens. That is corrosion.

Surface technology slows down or prevents this corrosion process. Protection against corrosion through innovative surface technology increases service-life and thus raises the value of the product or structural component. Collini provides numerous possibilities to combat corrosion.

By means of electro-plating, structural components can be protected against corrosion with suitable metal coatings.

Powder coatings form impenetrable barriers against oxygen and water and thus protecting the underlying structure.

Hot-dip galvanising protects steel parts by specifically inducing the corrosion process on the zinc surface. And only there!
Design - Surface creates.
Collini surface technology makes it possible to create products in such a way that they appeal to the varying aesthetic requirements and wishes of consumers. Design is more than the form and functionality of an object. In many cases, it is the aesthetics that adds to the value. The look, colour or structure of identical materials can be changed through different surfaces.

Powder coatings with its almost infinite possibilities in terms of colouring, degrees of glossiness and structures give products their true character. It is irrelevant whether it concerns machine cladding, vehicle components or architectural design elements.

High quality metal surfaces can be created with electroplating, the properties of which distinguish it clearly from that of the base material. Hence, products are refined and the required effects in finish and structure of the respective product
are created.

Hot-dip galvanised structural components with its crystalsilver surfaces are, besides the corrosion protection, often specifically included as design elements.
Tribology - Surface prevents wear.

Collini intensively deals with tribology: in other words, how friction and wear can be reduced or the lubrication between structural components can be improved. Because these factors are directly affected by the choice of the material, the surface coating and the surface topography.

Specially developed alloys and coating systems – Collini surfaces – reduce for example the energy input through the reduction in friction, increase the service life of bearing materials, plug contacts or improve the service performance of sliding contacts. Thereby the respective structural component can be manufactured from inexpensive basic materials. Then its required functionality – lower friction resistance or wear – is created with the coating system. By reducing friction and wear, energy and raw material resources are preserved and the service-life of products is increased. This is how Tribology contributes significantly to sustainability.

Technical data

Compare processes

	Zinc	Zinc-iron	Zinc-nickel
Processes	Galvanic zinc is deposited using acidic or alkaline electrolytes.	Galvanic zinc is deposited with an Fe content of 0.1 – 1% in the alloy.	Galvanic zinc is deposited with a Ni content of 12 – 15% in the alloy.
Coating colour	bluish white	silver grey	bluish white
Base material	Low alloy steel, spring steel, hardened steels, cast iron, non-ferrous metals	Low alloy steel, spring steel, hardened steels, cast iron, non-ferrous metals	Low alloy steel, spring steel, hardened steels, cast iron, non-ferrous metals
Corrosion protection	Depending on the layering system, up to 720 h NSST red rust, alloys > 720 h NSST red rust	Depending on the layer thickness, up to 1000 h in NSST red rust	Depending on the layer thickness, up to 1200 h in NSST red rust
Hardness	Depends on parameter settings	Depends on parameter settings	450 – 510 HV
Temperature resistance	up to 120 °C	up to 120 °C	up to 180 °C
System technology	Rack, drum	Rack, drum	Rack, drum
Conformity	RoHS, REACH, 2000/53/EC (End of life vehicle)	RoHS, REACH, 2000/53/EC (End of life vehicle)	RoHS, REACH, 2000/53/EC (End of life vehicle)
Execution	Natural zinc, passivated matte - thick film with a natural, yellow, black seal	Silver grey or passivated black, sealed and post-treated with lubricant	Metallic silver grey, black, bluish violet or yellowish brown, passivated, sealed and post-treated with lubricant
From our R&D	Collinox®	Collinox®	Ductalloy
Protective properties	Protection against corrosion, effects of lubricants, fuels, and solvents; thermally stable	Protection against corrosion, effects of lubricants, fuels, and solvents; thermally stable	Strong protection against corrosion, effects of lubricants, fuels, and solvents; thermally stable
Functional properties	Ductile, good slip properties, solderable, good primer for subsequent organic coatings	Ductile, good slip properties, good primer for subsequent organic coatings	Ductile, good slip properties, good primer for subsequent organic coatings
Decorative properties	Optical upgrading properties, matte to glossy, can be dyed through passivation	Optical upgrading properties, matte to glossy, can be dyed black	Technical coating, can be dyed black

Details

Typical components & applications

Typical components

Components for: Drives, internal combustion engines (ZnNi), chassis, brakes, steering, pipes and hoses, pipe connections, fittings, screws, nuts, bolts, hose connections, fastening components

Industrial applications

Automotive, commercial vehicles, the hydraulic industry, mechanical engineering, connection components, the construction industry, the furniture industry

Zinc surfaces in the portfolio

Zinc

Galvanic zinc coatings are used for the cathodic corrosion protection of steel and zinc die-cast components. The zinc coating dissolves first, thereby protecting the component against corrosive attacks. Corrosive attacks on the zinc surface can be greatly slowed down through the use of targeted post-treatments.

Galvanic zinc is deposited using acidic or alkaline electrolytes. The layer thicknesses are usually between 8 and 15 µm. The gloss level of the surface can be adjusted from matt to glossy by adding organic substances. The zinc coatings are so ductile that they can generally be deformed with the base material, but this diminishes somewhat when a very high gloss level is used.

After galvanisation, passivation is usually carried out to improve the corrosion protection of the galvanised surfaces. In passivation, there is a distinction between chromate coating and chromiumVI-free passivation systems.

Zinc-iron

Zinc-iron is a zinc alloy with an iron (Fe) content of 0.3% to 1%, which is characterised by high resistance to environmental influences. The zinc-iron alloy has improved corrosion resistance values compared to traditional galvanic coating, and with the corresponding passivations, deep black layers can be deposited. This means that zinc-iron is a technically better alternative for black surfaces in comparison to CDC and powder coating, as it also has a cathodic protective effect. Under corrosive stress, a firmly adherent, greyish oxide film forms on the surface, which cannot be removed.

Zinc-iron surfaces typically have layer thicknesses of 8 µm to 10 µm. These layers easily reach 480 h in the salt spray test against red rust.

Depending on the decorative specifications, the zinc-iron surface can be passivated in metallic silver-grey or black. Subsequent treatment with lubricant or sealant can be done. The adhesion of paints to zinc-iron is excellent.

Hydrogen embrittlement through the coating process can be prevented by subsequent heat treatment, which means that this process is also suitable for high-strength steel grades.

Zinc-nickel

Zinc-nickel is a zinc alloy with a Ni content of 12% to 15%. The zinc-nickel alloy ideally combines the corrosion inhibiting properties of zinc and nickel and provides very high resistance to environmental influences and weakly acidic media. Zinc-nickel surfaces typically have layer thicknesses of 5 µm to 10 µm. These layers easily achieve 720 h in the salt spray test against red rust, thereby complying with all current standards in the automotive industry. The removal rates in the corrosion test are approx. 1/10 of the removal rates of pure zinc layers. Therefore, depending on the layer thickness, significantly higher levels of corrosion resistance (>720 h) are possible. Zinc-nickel coatings are resistant to corrosion at temperatures up to 180 °C and are therefore also suitable for components in internal combustion engines where pure zinc coatings fail. For applications in which subsequent reshaping of the steel substrate is planned (e.g. straight pipes that will be reshaped), the special ductile variant Ductalloy® can be used. Even at the reshaped points, corrosion resistance of 720 h against red rust is achieved.

Zinc-nickel can be annealed by heat treatment. Zinc-nickel has the advantage of making this possible in the rational one-step process because the heat treatment has no negative impact on the passivation. Zinc-nickel is mainly used in components in the automotive industry, primarily in the engine and chassis area, areas with high corrosion stress. It is also used in commercial vehicles and in mechanical engineering and the hydraulics industry.