Abstract: The existence and rate of corrosion in a section of a well tubing or well casing string is determined and monitored continuously or intermittently by installing at predetermined locations as the string is placed in the well bore, sections of pipe that have been fitted with an array of piezoelectric transducers positioned around the circumference of the pipe and a microprocessor that controls signals going to and from each array of transducers and signals going to and received from controls and instrumentation apparatus located at the earth's surface. The apparatus can also include a reference block isolated from corrosion sources that is fitted with transducers associated with the microprocessor for the adjacent array of transducers. The microprocessors at varying locations along the string are electrically connected to the surface control and instrumentation apparatus by conductor cables and/or by wireless means using the pipe string as the conductive path for electrical signals.