Based on three processes, we present you with a complete solution for the automotive sector.


Based on three processes, we present you with a complete solution of surface coating for the automotive sector.

Reliable impregnation and plating process for intricate locking disc manufactured using powder metallurgy


A locking disc manufactured using powder metallurgy is part of a passive pedestrian protection system designed to minimise the consequences of accidents such as injuries. In the event of a head-on or similar collision with a pedestrian, the locking disc actuates a release mechanism that causes the bonnet of the vehicle to spring open just below the windscreen. The bonnet thus cushions the impact and reduces the risk of the pedestrian's head, for example, colliding with hard parts of the engine. The intricately designed disc fulfils an important unlocking function, which is why the long-term functional reliability of the component is absolutely essential. Here, corrosion resistance plays a key role, particularly in the exposed engine compartment area. The locking disc and the cams that interlock and connect in the event of a collision are made using powder metallurgy, as such intricate parts can hardly be manufactured using cutting or milling techniques.

However, despite their structural advantages, components made using powder metallurgy (sintered materials) have the disadvantage that they cannot simply be electroplated, making it difficult to improve their resistance to corrosion. Due to their porous structure, sintered components tend to absorb the aqueous liquids required during the plating process and gradually release them in the course of time. The resulting defect is known as "bleed-out" and causes salts to be deposited on zinc or zinc alloy electroplated surfaces. These salts frequently attack the plating, leading to localised corrosion on the sintered part. Although sintered components are usually impregnated prior to electroplating, the conventional processes adopted from the casting industry did not prove to be particularly successful for this purpose.

Solution with added value

With Sinter Surface Solutions, the Holzapfel Group has developed a complete solution for impregnation and plating that reliably prevents the defect known as bleed-out. For Sinter Surface Solutions, the impregnation process was specifically optimised by adapting both the process itself and the resins used, in order to meet requirements compatible with the plating process. The key innovation is the adaptability of the hardening process, which ensures that the pores are reliably impregnated to cover the entire surface of the component. This solution with improved impregnation, optimised hardening and special-purpose plating was also used for the locking disc.

Interesting for

The automotive industry, e.g. for transmission parts (rings, hubs and clutch bodies), for components in the engine compartment (gearwheels, bearing covers, sprockets) and in the steering system (pistons, guides)

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Benefit for the customer

The optimised impregnation process has a significantly positive impact on plating results. At the same time, in the case of the locking disc, the plating method was switched to a special zinc-nickel process that is ideally adapted to the specifications of the component and ensures flawless layer growth. The impregnation and plating made possible by the use of Sinter Surface Solutions enabled the component to be manufactured using the desired base material and the required surface. The method guarantees high resistance to corrosion and thus the long-term functionality of the locking disc.
The combined process makes it possible to reliably impregnate and electroplate all widely used types of components manufactured using powder metallurgy. Following impregnation, not only is it possible to apply anti-corrosion platings such as zinc or zinc-alloy systems, but also decorative surfaces and other high-quality finishes.