![]() ![]() Well the shiny pretty one is Zinc plating, and the plating is only typically 3 microns thick, the dull one is galvanised and is typically 50 microns thick and therefore provides much more protection. So when to use Zinc Plating, and when to use hot-dip galvanising?. A DC current is applied resulting in the Zinc being deposited on the product. Next, Zinc is deposited on the metal by immersing in a chemical bath containing dissolved zinc. Zinc plating (often called electro-galvanising which can cause confusion) is performed by cleaning the metal surface with an alkaline detergent, then treating it with acid to remove exiting rust. The finished product can be used up to 200 degrees celsius (above that the zinc can peel) It is the process of coating iron, steel, or aluminium with a thin zinc layer, by passing the metal through a molten bath of zinc at a temperature of around 860 ☏ (460 ☌). Hot-dip galvanising results in a metallurgical bond between zinc and steel. They are placed near and in electrical contact with the hull. Ships need not cover the hull with zinc anodes. Ships attach large blocks of zinc to the hulls to protect the hull from corrosion. All of the surfaces need not be covered with zinc. Zinc is also able to protect at a distance. When exposed to the atmosphere, the pure zinc (Zn) reacts with oxygen (O2) to form zinc oxide (ZnO), which further reacts with carbon dioxide (CO2) to form zinc carbonate (ZnCO3), a usually dull grey, fairly strong material that stops further corrosion in many circumstances, protecting the steel below from the elements. Zinc protects the steel by sacrificing itself – called a “sacrificial anode”. The duller galvanised finish can be seen on the left image, the shinier zinc plated finish on the rightīoth methods add a protective layer of zinc to the steel. But don’t be a magpie and just pick up the shiny object – think about the use. Zinc plating looks shiny and pretty, galvanised looks dull. Silchrome Plating carry out a wide range of processes from our production facility in Leeds, West Yorkshire and are fully ISO 901 accredited.When should you use galvanised steel or zinc plated steel?īoth add a layer of zinc to the outside of the product. For more information on the differences between the two, why not read our article HERE. ![]() At present Silchrome are still offering both Hexavalent and Trivalent based Passivates, but in the future we may only be able to offer Trivalent. As such many Zinc Plating passivates will now instead utilise Trivalent Chromium (Cr3) which addresses these environmental concerns. The passivation which is carried out in conjunction with Zinc Plating traditionally utilises Hexavalent Chromium (Cr6), this is a known carcinogen and in order to comply with REACH environmental standards alternatives have had to be developed. This coupled with the Zinc will provide the desirable attributes of corrosion and wear protection. As such the Passivation Process that follows Zinc Plating is a Chromate Conversion and will actually convert the metal surface into a complex mixture of Chromium compounds which will oxidise into a barrier layer. ![]() Now as above Zinc Oxide will not provide corrosion protection. Passivation is a non-electrolytic process which promotes the build-up of an oxide layer. As such White Rust would form on a component that was purely coated with Zinc. When other metals such as Aluminium react with Oxygen this forms a hard and protective oxide layer which is usually desirable, but a Zinc Oxide layer is soft and porous and does nothing to protect the component from corrosion. When Zinc reacts with oxygen it forms Zinc Oxide. The issue is that Zinc in of itself is a very reactive metal and would be susceptible to corrosion in contact with the air and in hot and humid conditions. In theory, yes if you wanted to you could just add a layer of Zinc onto your component. The process, commonly referred to as just ‘Zinc Plating’ is actually short for ‘Zinc and Passivate’ so what exactly is Passivation and why is it needed? Many different components are Zinc Plated in order to improve their part life and enhance their resistance to corrosion. You Asked: How do Passivates protect Zinc Plating?
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