The sensitivity of a permanently attached guided wave array for the detection of corrosion damage in plates is studied. The thickness reduction due to corrosion is modeled as a circular part‐through hole. The scattering and mode conversion of the A0Lamb wave mode is calculated numerically employing a three‐dimensional finite element model and verified in laboratory experiments. Good agreement is found and the sensitivity of the guided wave monitoring of large areas can be predicted. © 2004 American Institute of Physics