It was well known that residual carbon on the inner surface of copper tubes was a cause of pitting corrosion, and copper tube surfaces with different residual carbon amount were different corrosion forms. In this stud...It was well known that residual carbon on the inner surface of copper tubes was a cause of pitting corrosion, and copper tube surfaces with different residual carbon amount were different corrosion forms. In this study, the relation between corrosion form and elution of copper in immersion tests by accelerated corrosion test solutions was examined. Generally, pitting corrosion that occurs in actual machines was reported to observe chloride ion at the bottom of the pitting corrosion of copper tubes. Energy dispersive X-ray (EDX) mapping analysis indicated that chlorine was concentrated in the upper layer of the samples where copper was not detected under conditions of low residual carbon amount, while chlorine was concentrated under part of the micromounds (including the bottom of the pits) under conditions of high residual carbon amount. It was also suggested that the amount of copper eluted was related to the amount of residual carbon.展开更多
The investigations on the effect of the initial surface and microstructure on the seawater corrosion of Cu Ni alloy tubes were carried out by processing, electrochemical methods and natural seawater exposure as well a...The investigations on the effect of the initial surface and microstructure on the seawater corrosion of Cu Ni alloy tubes were carried out by processing, electrochemical methods and natural seawater exposure as well as SEM. Deformation had more impact on the final microstructure of the tubes than the annealing time did, and at the deformation of 32% and annealing temperature 550～600 ℃ for 1 h the tubes was completely recrystallized microstructure. As increasing the volume fraction of recrystallization, the homogeneity of microstructure and the corrosion resistance increased. The residual carbon film produced on the inner surface of the tubes during the processing, had higher corrosion potential than the alloy substrate and good electronic conductivity, so accelerating the dissolution of the substrate in seawater, and the non protective and loose corrosion product film formed. Immersed in natural seawater, the tubes of incomplete recrystallization, consisting of deformed and recrystallized grains, displayed intergranular corrosion, which resulted from corrosion micro cells built between deformed and recrystallized grains and the preferable transportation of electrons on the boundaries of both the grains. In contrast, the recrystallized alloy tubes formed the uniform and compact corrosion product film under which no corrosion was found.展开更多
文摘It was well known that residual carbon on the inner surface of copper tubes was a cause of pitting corrosion, and copper tube surfaces with different residual carbon amount were different corrosion forms. In this study, the relation between corrosion form and elution of copper in immersion tests by accelerated corrosion test solutions was examined. Generally, pitting corrosion that occurs in actual machines was reported to observe chloride ion at the bottom of the pitting corrosion of copper tubes. Energy dispersive X-ray (EDX) mapping analysis indicated that chlorine was concentrated in the upper layer of the samples where copper was not detected under conditions of low residual carbon amount, while chlorine was concentrated under part of the micromounds (including the bottom of the pits) under conditions of high residual carbon amount. It was also suggested that the amount of copper eluted was related to the amount of residual carbon.
文摘The investigations on the effect of the initial surface and microstructure on the seawater corrosion of Cu Ni alloy tubes were carried out by processing, electrochemical methods and natural seawater exposure as well as SEM. Deformation had more impact on the final microstructure of the tubes than the annealing time did, and at the deformation of 32% and annealing temperature 550～600 ℃ for 1 h the tubes was completely recrystallized microstructure. As increasing the volume fraction of recrystallization, the homogeneity of microstructure and the corrosion resistance increased. The residual carbon film produced on the inner surface of the tubes during the processing, had higher corrosion potential than the alloy substrate and good electronic conductivity, so accelerating the dissolution of the substrate in seawater, and the non protective and loose corrosion product film formed. Immersed in natural seawater, the tubes of incomplete recrystallization, consisting of deformed and recrystallized grains, displayed intergranular corrosion, which resulted from corrosion micro cells built between deformed and recrystallized grains and the preferable transportation of electrons on the boundaries of both the grains. In contrast, the recrystallized alloy tubes formed the uniform and compact corrosion product film under which no corrosion was found.
