Inhibitive action of stored olive mill wastewater (OMW) on the corrosion of copper in a NaCl solution

HPLC analysis shows that stored OMW is greatly enriched in phenolic compounds, mainly hydroxytyrosol (HT) (2.54 g L-1) and tyrosol (0.775 g L-1). But, after 4 years these compounds decrease in concentration. Potentiodynamic polarization measurements show that OMW acts as a mixed-type corrosion inhibitor for copper in 3 wt% NaCl solution. The exceptional effect of this inhibitor is above Ecorr. The full passivation range greatly increases upon the addition of inhibitor and increases further with increasing OMW concentration. For sufficiently-high OMW concentrations, a notable absence of trans-passivation phenomenon until 2500 mV is detected and no pits are observed on the samples' surface.