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Among the most sophisticated chains produced by ZMC, are those employed in the automotive pre-treatment process.

The application of protective layers that precede the final painting of the cars, vans and trucks, takes place in pre-treatment plants, through which the chains follow the path of a sine wave. Two parallel chains slide on side guides which support steel carriers and in turn carry the car body.

The process of applying corrosion inhibiting layers is achieved by conveying the car body through chemical baths. The nature of the conveyor path, having many rises and falls, is called the Pendulum system, and the chains take the same name.

More recent systems allow the car body to also be rotated inside the chemical bath for more effective surface coating, this type of system is called Ro-Dip.

There are significant technical challenges to be considered in providing chains that operate in these applications. The chains are highly stressed from a mechanical and corrosion resistance point of view. Innovative features include the choice of materials suitable for the operating environment, (in some cases Duplex stainless steel) the design and construction of sturdy bearing wheels, and an internal lubrication facility to operate with automatic lubrication systems.



Chains with copper plated pins

The copper plating of the pins is historically a typical and recognizable feature of various ZMC chains.

The galvanic copper coating is performed on the pins of our chains for precise technical reasons that involve both the quality of the product and safety at work.

The riveting operation concludes the assembly of the chains, it provides a plastic deformation of the head of the pins to ensure the mechanical resistance in the presence of axial thrusts.

To obtain an effective riveting it is necessary that the pins are not excessively hard, the same characteristic is important to prevent metal splinters from detaching and being projected in the surrounding area while the component is undergoing deformation.

The resistance to wear of the chain, however, would require exactly the opposite, that is a pin with the highest possible surface hardness.

The copper plating intervenes precisely to find a solution to these two opposite requirements. The pins are completely coated with copper, afterwards they are ground on the cylindrical and the coating remains only on the heads. During the heat treatment process, copper inhibits the spread of carbon in the metal matrix of the steel, so that the areas covered with copper do not harden. At the end of the process the copper-plated pins of ZMC have both the ideal characteristics: high hardness of the cylindrical part, such as to guarantee the best performance of resistance to wear, and a soft head, easy and safe to rivet.

A further advantage guaranteed by copper plating is the protection against oxidation that the galvanic coating guarantees to the pin head, including the area of press fit with the plate.

For more information, don’t hesitate to contact us