chapter  7
15 Pages

Metal Coatings

Under most conditions, non-ferrous metals are more corrosion resistant than carbon steels. However, they are more expensive and, for many purposes, do not have the required mechanical properties. The advantages to be gained by combining the properties of the two groups of metals by coating steel with a non-ferrous metal are clear. Zinc has been used to coat steel articles for over a hundred years and many other examples of metal coatings are commonplace, e.g. chromium plate for car trims. Metal coatings can be applied for decorative and engineering purposes, e.g. for hard facings. However, as these are not primarily for steel protection, they will not be considered here. The metals most commonly applied to impart corrosionresistance properties to constructional steelwork are zinc and aluminium. Of these, zinc is by far the most widely used. Other metals and alloys are also used to coat steel in certain critical situations, e.g. ‘Monel’. Although they will be discussed, such alloys are not used as general protective coatings for steelwork.