Since January 1976, safety seatbelts have been mandatory in new vehicles in Germany, playing a vital role in saving lives daily. The metal components used in seatbelts must meet stringent requirements for mechanical strength and long-term durability. Traditionally, these requirements have been met using galvanically separated protective layers made from nickel and chrome.
However, the use of chrome(VI) compounds in these coatings has come under scrutiny due to the REACH regulation. In response, ZF LIFETEC has upgraded its galvanizing facility and transitioned to an advanced chrome(III)-based system. This change, implemented in 2023, was carried out in close collaboration with Dr.-Ing. Max Schlötter GmbH & Co. KG, who also planned and executed the necessary conversion work.
Passenger cars typically use three-point seatbelts, which require metal components that are not only resilient but also stable under varying climatic conditions. At the same time, these components must meet high expectations for their aesthetic appearance. “For safety systems like these, the metal components must maintain both their functionality and appearance under challenging conditions,” explains Thomas Haberfellner, COO at Dr.-Ing. Max Schlötter GmbH & Co. KG.
The components are coated with electroplated nickel and chrome layers and often overmolded with plastic in specific areas. During use, the functional nickel and chrome surfaces are exposed to high levels of corrosion and friction.
In anticipation of regulatory changes in European chemical laws, ZF LIFETEC has adopted the chrome(III)-based system, offering a forward-thinking solution that also supports the automotive industry. The company has turned to Dr.-Ing. Max Schlötter GmbH & Co. KG, which has extensive experience researching and developing chrome(III)-based electrolyte systems. These electrolytes provide a fully viable alternative to traditional chrome(VI) systems for such applications.
Before coating, the metal parts are produced in precise manufacturing steps during which they are punched, deburred, hardened and pre-finished by vibratory grinding. The advanced vibratory finishing process at ZF LIFETEC, not only reduces processing times in parts production, but also prepares the surfaces for optimal galvanic coating. In the fully automated galvanising lines, the parts are degreased, nickel-plated and finally chrome-plated so they can fulfil demanding requirements for corrosion resistance and aesthetic appearance.
In advance of the changeover, comprehensive testing and adjustments to the technical equipment had to be carried out before the properties of the established coatings were attained. With the Chrombad SLOTOCHROM BC 4130 brand name, Schlötter is offering the latest development stage of chrome(III) systems.
