The distribution of copper, iron, phosphorus, lead, and sulfur in the corrosion layers of old patinated copper and bronze was analyzed by energy dispersive x-ray in the scanning electron microscope. The distribution patterns show that the content of copper decreases towards the surface while the content of iron increases. With increasing thickness of the corrosion layer the migration of copper ions is drastically reduced so that element species from airborne particles prevail in the outer corrosion layers. It can be shown that the deposition of the dust particles not only prevents a further build-up of the protective patina, it even weakens the patina layer through chemical and physical processes taking place in the outer corrosion layers to such an extent that its protective effect is lost.