A method is presented to test the persistence of inhibition of corrosion of copper in previously inhibited tap water. Cyclic voltammetry (CV) sweeps on copper were carried out in tap water both in the presence and in the absence of inhibitor to examine the state of passivity and of breakdown leading to localised corrosion of the metal in tap water in order to investigate the persistence of inhibitor. The results show that after prior inhibition and re-immersion in inhibitor-free tap water, inhibition is still observed and persists through several further potential cycles. These novel observations describe the persistence of the inhibitor on the surface after the supply of the inhibitor has been removed. (C) 2016 Elsevier Ltd. All rights reserved.