Zinc metallisation

Up to 120 xm of zinc can be deposited by plasma metallisation. Experience has shown that this coating is not very effective and has a poor resistance to seawater. The coating being porous, the attack of zinc by seawater results in very voluminous corrosion products that lead to the formation of blisters at the interface between the metal and the coating [34]. The difference in potential between aluminium and zinc, approximately 400 mV, is too high. 

Zinc coating of 5000 and 6000 series alloys for classic marine applications seems to be unnecessary and superfluous, because these alloys show an excellent corrosion resistance in marine environment. Zinc coating has no advantage, and moreover, its corrosion resistance is precarious. 

On the other hand, industrial equipment such as regasification plants for liquid natural gas operating by seawater spraying and located in closed and polluted sites are usually protected by thermal or plasma projection coatings with aluminium-zinc alloys, and are additionally protected with specific paints. 

The word inhibit is derived from the Latin word inhibere , which means to stop, to refrain. The word inhibition has been used in chemistry and in corrosion science since 1907. 

The idea of using inhibitors is very old, going back to the Middle Ages armourers used to add flour or yeast in order to prevent fragUisation of the weapons during acid pickling [35], The role of chromates was discovered around 1910 sodium silicate has been used as an inhibitor on aluminium since 1929 [36]. Inhibitors are substances (or a combination of substances) that, added in a low concentration to an environment, will cancel or reduce its aggressiveness towards a metal. 

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Flame spray metallising is widely used for the protection of metal against corrosion, especially for in situ protection of stmctural members. The principal metal used for spraying of plastics is sine. Aluminum and copper are also used. If the distance from the part is too great, the zinc solidifies before it touches the part and adhesion is extremely poor. If the molten zinc oxidizes, conductivity and adhesion are poor. If the distance is too short, the zinc is too hot and the plastic warps or degrades. These coatings are not as dense as electrically deposited coatings because of numerous pores, oxide inclusions, and discontinuities where particles have incompletely coalesced. 

Kretzschmar, E., Metaii, Kermik and Piasispritzen, V. E. B. Verlag Technik, Berlin (1970) Leclercq, M. and Bensimmon, R., New Zinc-based Alloy for Metallising . Proc. 8th Int. Thermal Spray. Conf., American Welding Society, pp. 417-429 (1976)... 

Aluminium is widely applied for decorative and protective requirements, while cadmium , zinc and titanium have been applied to ferrous materials chiefly for their protective value. The method finds particular application in the plating of high-tensile steels used in aviation and rocketry, car fittings and lamp reflectors, and gramophone record master discs, as well as in the preparation of specimens for electron microscopy and in rendering insulated surfaces electrically conducting, e.g. metallising of capacitors and resistors. 

Delpeuc h, Y. (1972). La protection de I acier par des revetemcnts de metallisation au zinc et k I aluminium (Protection of steel by zinc and aluminum metallized coatings). Corrosion, 20(6), 416-420 (in French). 

In order to make a metallised film capacitor the polymer has a layer of either aluminium or zinc vacuum evaporated on to its surface. Once the capacitor has been wound a gradually increasing potential known... 

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