ABSTRACT
The atmosphere in the UK and elsewhere, depending upon whether the location is rural, coastal, suburban or industrial, can be polluted by gases such as sulphur dioxide, hydrogen chloride, ammonia, carbon monoxide and carbon dioxide. The sodium chloride content of marine, coastal atmospheres is less aggressive to aluminium than the industrial pollutants, and so generally aluminium is regarded as a good material to use in marine environments. The oxide darkens to a degree that is dependent upon the amount of the atmospheric pollution, its situation relative to the cleansing action of rainwater, the amount, if any, of maintenance and cleaning applied. In the interiors of domestic, office buildings, where the atmosphere is usually clean, there will be little change in the appearance of the metal apart from perhaps a slight dulling and darkening in certain areas. Rainwater has a cleansing action on aluminium, and in the main, surfaces exposed to the elements suffer less pollution damage than more sheltered ones.
