metal corrosion
Decorative, or constructional metal in buildings can be susceptible to corrosion, the commonest form is due to gases and particles present in the atmosphere, (carbon dioxide and sulphur compounds in particular). Other environmental factors such as heat and humidity will affect the rate of corrosion, for example, in marine areas chloride and other salts in the atmosphere will speed up corrosion significantly. Historically masonry was often constructed using iron cramps and dowels. When these rust they can cause severe distortion and cracking to the stone (see also Rust). (Siker, 2018)