Internal Corrosion of Copper-Nickel alloy tubes 90/10 and 70/30 in Chlorinated Seawater for Shell and Tube Heat Exchangers

摘要

The corrosion resistance of copper-nickel 90/10 and 70/30 tubes for heat exchangers was evaluated in 0.5 ppm-chlorinated seawater, under controlled service conditions in a bespoke test loop. The results were compared to Al-Brass tubes tested under the same conditions. Copper-Nickel 90/10 tubes were tested with two different geometries: internal smooth surface and internal finned surface (helix geometry). Internal pitting corrosion resistance was evaluated under simulated heat transfer conditions at two controlled skin temperatures from the internal and the external parts of the tubes for 6 months, at 50°C_((Tskin-in))/35°C_((Tseawater)) and 70°C_((TSkin-in))/35°C_((Tseawater)). For all the tested copper alloys, the uniform corrosion was very low and negligible. For both temperatures, CuNi 90/10 was globally more resistant to localized corrosion than CuNi70/30. The most corrosion resistant configuration was the CuNi 90/10 with the internal finned geometry. The best corrosion resistance compared to the smooth geometry might be attributed to different hydrodynamic conditions at the seawater/metal interface.