Report concerning the corrosion behaviour of CuNi10Fe in seawater, based on investigations carried out at Royal Naval College of the Royal Netherlands Navy. The testing program included exposition to flowing seawater, tests aimed at determining the erosion behaviour, electrochemical measurement of polarization behaviour, corrosion potential and polarization resistance, and electron microscopic investigations into the structure and composition of protective layers. The tests were carried out with natural and synthetic seawater in the laboratory and under conditions encountered on ships. Studies made with the electron microprobe reveal that the protective layers are of a very complex structure and that the formation of a really protecting layer requires two weeks' time. The protective action is due to concentration polarization because of the reduction of oxygen and oxidation of copper (due to concentration phenomena in pores) and to a reduction of the active surface.
Constructing under water has accelerated research into corrosion protection and antifouling properties of materials used below the seawater level. A special working party was founded in the Netherlands to study — theoretically and practically — the corrosion and fouling properties of materials and coatings. A special test rack was immersed at a depth of 50 m in the North Sea in 1969. Experience gained from these experiments gave rise to a joint investigation by 13 laboratories in the Netherlands; the programme involves ten test racks 50 and 100 m below sea level, in the tidal zone and in marine and land atmospheres. The materials studied were: steel with various paints and coatings; stainless steel, Cu, Al and Ti alloys; welded, brazed, nailed and glued stainless steel, Al and Ti alloys; synthetic fibers. The test methods included crevice corrosion and stress corrosion bending tests, electrochemical measurements and the regular control of the biological conditions. The results show the importance of testing in specific marine areas because the results are not readily applicable to conditions in other geographical regions.
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