The spatial and temporal evolution of the components of a plasma surrounding a 90° convex and a 90° concave electrode whose potential is suddenly decreased in a three‐component plasma is numerically investigated. The quasineutral plasma consists of positive ions and various proportions of negative ions and electrons. The results are compared and contrasted with those that are obtained in a normal two‐component plasma. The transient or ion matrix sheath is identified and its subsequent evolution is investigated. Effects of perturbations in the electrode are investigated. ©1996 American Institute of Physics.