9.1 The aluminium components of the system will perform effectively, without maintenance, for a period of 30 years in rural or suburban surroundings, or 20 years in severe industrial surroundings(1).
(1) Excluding the immediate vicinity of, and downwind from chemical plants, copper foundries, cement works and other factories which produce contaminants particularly corrosive to aluminium.
via http://www.alifabs.com/building-products/Building_Products_BBA_Certificate.pdf
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