Here at EC Williams, we are proud to be market leaders in electroplating services. This includes zinc nickel plating. This type of plating service is incredibly popular and can be used in a wide range of industries. But, before you invest in the service, it’s important you know everything you need to know about the service. So, what is zinc nickel plating?
What is zinc nickel plating?Sacrificial, anodic coatings, specifically zinc deposits, have provided corrosion protection to components and parts across many industries. There is an increasing demand in the automotive and industrial sectors. Today, typical sacrificial applications for fasteners, fuel systems, braking systems and drive assemblies require an increasing demand for higher corrosion performance from anodic coatings. There is the ability to design electrochemical alloys to provide the highest corrosion potentials to meet these increased demands. Today zinc-nickel alloy systems deposited from alkaline and acid chemistry types perform well in many applications. However, it is important to compare and contrast these deposits and the systems that provide the zinc-nickel alloys. This is because you will then have good knowledge basis for selecting the best system for your application.
The Increasing Popularity of zinc-nickel DepositsIn the last decade, electroplated zinc-nickel deposits have become increasingly requested. The main reason for this is the ability of zinc-nickel to offer excellent corrosion protection when applied over ferrous substrates. Galvanic corrosion happens in an aqueous environment, such as a 5% neutral salt solution. The two metals with different electrode potentials come in contact with one another. As a result, the sacrificial metal, with a more negative potential, loses electrons and oxidizes to become an aqueous cation. The greater the difference in potential between the two metals, the faster this dissolution happens. Reactive metals such as zinc and magnesium have a more negative potential compared to cast iron and steel. Noble metals like silver and platinum have a less negative potential. Zinc-nickel is sacrificial to cast iron and steel, though not quite as sacrificial as pure zinc. In this way, a zinc-nickel layer over steel would corrode less quickly than a pure zinc layer of comparable thickness. Cadmium has a very close sacrificial potential to steel. This will usually provide superior corrosion resistance in a salt water environment. However, cadmium and its compounds have a well-known toxicity. As a result, zinc-nickel deposits are a more environmentally safe alternative.
Corrosion ResistanceOf particular interest in the zinc-nickel alloy system is the gamma phase zinc-nickel (γ Zn-Ni). This is because it has been widely accepted that γ Zn-Ni provides better corrosion resistance and ductility than other phases. This is when you apply it over cast iron or steel. The binary phase diagram in Fig. 33 depicts how the majority of this γ phase is found when the nickel content ranges between 14 – 25 wt% in a temperature range of 0 – 700°C. In the electroplating industry, a deposit containing between 12 – 16 wt% nickel is usually what is specified and desired. However, specification ranges may be opened to 10 – 18 wt%.
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