PO43- ions as corrosion inhibitor were investigated on copper in tap water in the presence of NaClO. The inhibitor was evaluated by electrochemical techniques and weight loss tests. Raman spectroscopy and X-ray photoelectron spectroscopy were used to study the passive layer. In inhibited tap water, the passive layer is thick and compact if NaClO is present. Weight-loss tests showed the inhibition of uniform dissolution and no pitting attack. When adding NaClO, Cu-3(PO4)(2) is incorporated to the passive film. Thus, phosphate ions are effective as inhibitors for copper in tap water, even when using high dosages of biocides. (C) 2013 Elsevier B.V. All rights reserved.