CHEMISTRY

Electrochemical Technology

Electrochemical Technology

Answer: 1

The conversion coatings also known as the passive treatments, are the covering or vanishing of the metal surfaces in which the surface of the metals are covered with the coating of some other substance with the help of the chemical reaction or the electro-chemical process. There are several kinds of conversion coatings that are being done to cover the metal surfaces. These include the anodizing, the phosphate conversion coatings, black oxide which is done, on steel and the bluing. The most common conversion coating that is used as a covering layer is chromate conversion coating. All these coatings are used for the protection of corrosion, to increase the hardness of the surface, to add the colour as the painter primers. The conversion coatings are of different thickness varying according to the reactivity of the metal to which the covering needs to be applied. Thick coverings are applied to the metals like zinc (Fan, 2012, pp. 32-38).

The conversion coatings are routinely applied on the zinc based metals in order to increase the durability of the zinc based metals. There are several improvements that the conversion coatings due to the properties of the zinc based metals. The covering acts like the paint shielding the zinc from the process of white corrosion. This increases the durability of zinc, and it depends on the thickness of the coat or cover. The shielding layer provided by the conversion coating and the protective effective of that layer on the zinc based metal can be identified by the change in the colour. The colour of the zinc based metal succeeds from the colour blue to yellowish gold and then to the olive green, after this colour, the colour of the surface changes to black colour. The colour is not the complete indicator of the process or the covering because the surface colour may also be changed by using the dyes. The coverings darker in the colour provide more corrosion confrontation as compared to the lighter coverings (Oki, 2012, pp. 59-64).

Chromate conversion coating is a chemical covering that passivates the metal bases such as zinc, aluminum, silver, copper, tin, cadmium and magnesium. The chromates have been used for the metal bases covering purpose from a very long time. The chromates are famous for retaining the electrical conductivity of metals, and this was the significant reason that they were widely used for the conversion coatings. The process of the chromate conversion was named after the chromate present in the chromic acid which was in turn use, in the bath, and is known as the Hexavalent Chromium. There are many features that the chromate conversion provides to the metal base surfaces such as a good and smooth base for the paint applications, protects the surface from corrosion, enhance the electrical properties and is easy to apply. The chromate coatings are sticky and soft when they are first applied to the surface, but after some time the coating becomes hard and ...