Though the metal steel used for your watch is highly rust-resistant, rust can form if your watch is not cleaned after it becomes dirty.
Dirt on your watch can make it impossible for oxygen to come into contact with metal, which can lead to breakdown of the oxidization layer on the metal surface and the formation of rust.
Rust can cause sharp areas on metal components and can cause band pins to fly out of position or to fall out. If you ever notice any abnormality immediately stop using your watch and take it to our original authorized retailer or to an authorized Casio approved service center. (customer will be charged)
Even if the surface of the metal appears clean, sweat and rust in crevasses can soil the sleeves of clothing, cause skin irritation, and even interfere with watch performance.