THE answer to rust for 30 years

The Holzapfel Group has more or less "grown up" with zinc-nickel. Our company history began in 1949 with the "Holzapfel galvanising plant and precision mechanics workshop", founded by Willy Holzapfel in Wetzlar. In those days, galvanic nickel plating was still the company's main source of income. As early as 1987, we were the first industrial plating service provider to offer zinc-nickel plating. The process soon became our "bread and butter" and thus made a significant contribution to our commercial success.

The birth of zinc-nickel plating

Zinc-nickel plating was developed to respond to the increasing need for the automotive industry in particular to protect its components from corrosion caused by fluctuating temperatures, de-icing salt and climatic changes. For example, zinc alone no longer provided sufficient corrosion resistance when exposed to high temperatures. A further challenge was the increasing percentage of aluminium components in the engine compartment, which led to the problem of contact corrosion associated with zinc. In addition, thin layers and high corrosion resistance were required for dimensionally stable platings.

The beginnings

Hans-Ludwig Blaas, Managing Partner of the Holzapfel Group at that time, undertook initial trials with zinc-nickel in 1987. The first small series for an automotive manufacturer were also produced with a great deal of manual effort using a test bath with a capacity of only 150 litres.

After achieving positive test results, in 1987 a new facility was installed in our Fleisbach plant for the then still acidic ammonium chloride Zn/Ni process with 12-16% Ni content. After conducting large-scale trials, series production finally started with a 5,000-litre bath. The first component to be mass-produced with a zinc-nickel plating was a gas regulator holder for an OEM whose galvanised surfaces had already experienced corrosion and considerable problems "in the field" during the validation phase. The OEM soon became convinced of the significantly longer service life of Zn-Ni-coated parts, especially the protection the plating provided from red rust. The gas regulator holder was first produced in 1987 and installed in several types of vehicle. By the late 1990s, Holzapfel had coated several million of these parts.

Despite the excellent technical properties of the Zn/Ni plating and increased protection from corrosion, our potential customers were sometimes concerned at first. "Zinc-nickel has a matt surface and looked different to the yellow chromated, glossy zinc layers that were common at the time," says Blaas. "We were therefore in a situation where we had to sell a visually less attractive zinc-nickel plating as if it were the better solution, although it was supposedly worse from the customer's point of view."

Capacity expansion and further process development


It took a few years, but when zinc-nickel and its technical advantages were confirmed in the field and its lobby in the automotive industry was established, there was no longer any way of getting around the process. The success of the zinc-nickel process led to larger premises and installing additional facilities. We also continued developing the process, which led to the introduction of the flexible and bendable Zn-Ni FleXXKorr zinc-nickel plating in 2008. Today, at the Holzapfel Group we have four systems specially designed for zinc-nickel plating and thus maintain high capacities. "All in all, we now have Zn-Ni capacities with a bath volume of more than 200,000 litres at our disposal, which makes us probably the world's largest supplier of zinc-nickel rack-plated goods," says Hans-Ludwig Blaas.

Zinc-nickel for lightweight construction and electric mobility

"The successful development and application of zinc-nickel has contributed to evolution in the automotive sector and it can still become the key technology for state-of-the-art lightweight construction." That is the conclusion of an OEM who witnessed the beginnings of the process from the customer's viewpoint. Zinc-nickel protects better against corrosion, considerably extends service life and is available globally. Further advantages of the zinc-nickel process with nickel insertion rates of 10 to 15% are its compatibility with aluminium (no contact corrosion), bondability and electrical conductivity. The process is also suitable for lightweight construction applications, such as for plating ultra-high-strength steels, where it can reduce liquid metal corrosion and hydrogen-induced brittle fracture. Used in composite design, Zn-Ni-coated components can reduce contact and crevice corrosion.

The process can also help master the challenges of e-mobility, as zinc-nickel coated surfaces make it possible to create contact in the high-voltage range as well as grounding and have a positive effect on disruptive wear.

The use of zinc-nickel platings in layer systems has a great deal of potential for other interesting fields of application.