Oxide of iron
Things which are made of iron will react with moisture in air and change into red color. Iron starts falling in small amounts and this layer is called as rust. Rust is oxide form of iron and it is formed when iron reacts with oxygen. When water falls on iron substance, iron reacts chemically with oxygen in water and forms rust. Water gets evaporated. Any substance which is rusted will form rust further when it is placed in dry air. The reason for this is that rust on the upper layer of iron will detect small amounts of moisture also. So iron articles should be protected before itself. To prevent rust formation on iron objects, a type of plastic layer or paints are used. In the case of iron ships which will always be in water, rubber paints are used on the underside of ship to prevent rust and de humidifiers are used to send the moisture content air outside. Wounds which are formed due to rusted things or falling of rust on wounds is also dangerous. Consulting a doctor should be done in these cases.