Impressed current is a method used to protect metal structures from corrosion, particularly in environments where moisture is present. This technique involves applying a direct electrical current to the metal, which counteracts the natural electrochemical processes that lead to rust and deterioration. The impressed current system typically includes an anode, which is placed in the ground or water, and a power source that supplies the current. This method is commonly used for structures like pipelines, bridges, and marine vessels, helping to extend their lifespan and reduce maintenance costs.