The main cause of damage to church ironwork is oxidation corrosion: a reaction with oxygen in the air causes rust to form.
Rusting is more likely when one or more of the following apply:
- high moisture levels
- high levels of salt in the air (e.g. seaside conditions)
- high levels of pollution
- damage to the paint or other protective coating
Over-cleaning of metallic objects can damage decorative elements made of softer metals, or destroy protective coatings such as galvanising.