Understanding localized corrosion mechanism of 90/10 copper-nickel alloy in flowing NaCl solution induced by partial coverage of corrosion products films

The galvanic effect induced by partial coverage of corrosion products films is studied for 90/10 copper-nickel alloy in flowing NaCl solution using electrochemical and surface analytical methods, aiming at understanding the localized corrosion mechanism. The results show that small-area bare samples act as cathode with polarity reversal and anode after coupled to statically and dynamically pre-filmed samples for 240 h, respectively. The latter indicates higher localized corrosion risk, especially at high flow velocities of 3.3 m/s and 4.2 m/s. The localized corrosion mechanisms are explained based on evolution of corrosion products films during coupling.