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Immersion zinc plating is an electroless (non-electrolytic) coating process that deposits a thin layer of zinc on a less electronegative metal, by immersion in a solution containing a zinc or zincate ions, Zn(OH) 2− 4. A typical use is plating aluminum with zinc prior to electrolytic or electroless nickel plating.
Zinc is considered a reliable material, but is not suitable for use at higher temperatures, as it tends to passivate (the oxide layer formed shields from further oxidation); if this happens, current may cease to flow and the anode stops working. [10] Zinc has a relatively low driving voltage, which means in higher-resistivity soils or water it ...
Aluminum sacrificial anodes (light colored rectangular bars) mounted on a steel jacket structure. Zinc sacrificial anode (rounded object) screwed to the underside of the hull of a small boat. Cathodic protection (CP; / k æ ˈ θ ɒ d ɪ k / ⓘ) is a technique used to control the corrosion of a metal surface by making it the cathode of an ...
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Many steel objects are coated with a layer of zinc, which is more electronegative than iron, and thus oxidises in preference to the iron, preventing the iron from rusting. [4] Similarly, sacrificial bars of a metal such as aluminium or aluminium alloys can be attached to an oil rig or to the hull of a ship to prevent it from rusting and ...
The Hull cell replicates the plating bath on a lab scale. It is filled with a sample of the plating solution and an appropriate anode which is connected to a rectifier. The "work" is replaced with a Hull cell test panel that will be plated to show the "health" of the bath.
A common example of galvanic corrosion occurs in galvanized iron, a sheet of iron or steel covered with a zinc coating. Even when the protective zinc coating is broken, the underlying steel is not attacked. Instead, the zinc is corroded because it is less "noble". Only after it has been consumed can rusting of the base metal occur.
Certain metals, such as zinc, may become embrittled from the hydrogen gas which is evolved at the cathode. The anodic process avoids this effect since oxygen is being generated at the anode. The major advantages that are normally touted for the cathodic processes are: Higher levels of corrosion protection are possible.