A corrosion inhibitor for water is a chemical compound that is added to water systems to prevent or reduce the corrosion of metal surfaces. These inhibitors work by forming a protective film on the metal surface, which acts as a barrier between the metal and the corrosive elements in the water. Common types of corrosion inhibitors for water include organic compounds, inorganic compounds, and mixed inhibitors. They are widely used in industrial water treatment, cooling systems, and other applications where metal corrosion can be a problem.