What does it mean for metal to rust in the first place? Generally, the phenomenon of "rusting" refers to the process by which metal releases electrons and becomes ionized. In other words, this is called "oxidation." Additionally, there is a term "reduction" that is paired with "oxidation," and both oxidation and reduction occur through the transfer of "electrons." The substance that forms on the surface of the metal due to this phenomenon is commonly referred to as "rust." There are several types of rust, and the most well-known is probably iron rust. Iron rust has several common names depending on its state. Next, a well-known type is verdigris. This is a green rust that occurs when copper oxidizes, and there is also zinc rust, which is referred to as white rust. Thus, even though we refer to it simply as "rust," there are various types, and many colors and properties exist. There may even be types of rust that have not yet been discovered. However, the phenomena of "rusting" and "oxidation" are singular, so we can take measures according to the specific situation.