[TN41] Clear Protective Coatings for Copper and Copper Alloys

© European Copper Institute

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Detailed description of the range of coatings available with application methods and recommendations for use.

Copper and copper alloys such as brass and bronze are well known for their strength, corrosion resistance and attractive colours. This range of properties has resulted in their use in a wide variety of applications for both functional and decorative purposes.

In architecture, for example, copper is an ideal roofing material. It is beautiful and durable requiring little or no maintenance and it can be applied easily and economically. It is also comparatively light in weight when considered against other roofing materials, so that savings can be made in the timber substrates. Copper cladding provides an elegant and durable facade to buildings, and copper alloy railings and ballustrades create a sophisticated finish.

Brass is one of the best materials for architectural hardware because of its attractive colour and corrosion resistance. It is widely used for such items as handles and locks and letterboxes. Inside buildings it adds a touch of sophistication to switch plates, socket covers, handrails, taps and lamps along with numerous other fixtures and fittings.

Copper itself and many of its alloys tarnish slowly when exposed to the atmosphere. In some applications, for example roofing, the effect of this gradual colour change is actively sought after. Architects may choose to design with this in mind, knowing that after a few years the roof will have taken on an attractive green patina. It is also possible to produce this patina by chemical treatment, so that the appearance of any stage in the weathering process can be chosen. The surface can be preserved at any stage by the application of a clear protective coating.

A bright polish on brass hardware items can be protected using tough, abrasion-resistant coatings thatwill withstand daily handling and use. Decorative items also, from inexpensive brass ornaments to unique bronze sculptures, both ancient and modern, can be protected from the atmosphere, and theirbeauty preserved, by the application of an appropriate clear coating.

There is an enormously wide range of such clear coatings available, many of which are formulated forparticular service conditions, and it is essential that the most appropriate coating is chosen for each application. Inappropriate choice of coating will lead to failure in service and rapid deterioration of the appearance of the metal surface.