An erosion sensor that can separately monitor erosion and corrosion of a substrate, such as a wind turbine blade or a turbine blade used in devices such as gas turbines, aircraft engines, microturbines, steam turbines, and the like is disclosed. The sensor can include a first element or “erosion part” that is made of a corrosion resistant material. The first element of the sensor has similar erosion properties to the substrate being monitored. The sensor can further include a second element or a “corrosion part” that is made of a material having similar erosion and corrosion properties to the substrate. The sensor can provide an erosion indicator based on the erosion of the first element and a corrosion indicator based on the erosion and corrosion of the second element.