This paper reports the results of corrosion tests performed on 254SMO and 2507SAF stainless steels and titanium, in flowing seawater at 60 degrees C. Tests were performed at Mareco CNR marine corrosion laboratory sited in Bonassola (La Spezia, Italy) for four months. The evolution of corrosion phenomena were followed by means of online simultaneous acquisition of open circuit potential (OCP), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and electrochemical noise analysis (ENA). Moreover, the effect of antiscaling and biocide water treatment on corrosion behaviour of selected metals, was studied. At the end of test, samples were dismounted and inspected by visual and microscopic observation. As a general trend, a good behaviour was observed for all materials. A strong, positive effect of the water treatment was detected in particular on titanium.