Phosphate ions as inhibiting agents for copper corrosion in chlorinated tap water

PO43−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, Cu3(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.

► Changes in the copper corrosion after adding phosphate to tap water were analyzed.
► When NaClO and phosphates are present, Cu3(PO4)2 participates of the surface film.
► In the absence of biocide the surface film contains a mixture of Cu2O, CuO and Cu(OH)2.
► PO43− is an effective inhibitor for Cu in tap water containing high NaClO dosages.