The present invention is a mechanical oscillator metal loss sensor for use in a corrosive or erosive environment. The elements include a means for mechanical excitation, and a mechanical oscillator with two regions that corrode differently, where the regions are determined to affect specific influences on the resonance parameters, wherein said mechanical oscillator has a resonant frequency, f, and a quality factor, Q. In a preferred embodiment, the mechanical oscillator has the shape of a tuning fork.