The use of rotating cylinder electrodes for the investigation of aqueous erosion-corrosion has determined that they are suited to the task with some minor modifications. The requirements that need to be met to ensure that true turbulence is produced within a cell to allow reproducible investigation of a range of erosion corrosion parameters have been elucidated. The cell must operate above Taylor numbers of 15000 and as such large annular gaps and higher temperatures are beneficial. Careful consideration of the conditions required needs to be made before designing a rotating cylinder for the study of erosion corrosion. The use of outer cylinder static electrodes has been determined, through mass transfer tests to be valid for a small annular gap of 5mm, allowing experiments to be set up in autoclaves that reproduce hostile process plant parameters. Fixed potential studies of the erosion corrosion of mild and chromium steel in deaerated 1M NaOH have determined that over the majority of the potential range studied there was no synergistic effect between corrosion and erosion. The erosion-corrosion rate was just the sum of the corrosion rate during erosion and the erosion rate in the absence of corrosion. Over a small potential range in the transpassive corrosion region of the chromium steel a negative synergistic effect was determined. In this region, the transpassive corrosion of chromium from the steel inhibits the erosion of the metal by impacting particles. The effect of particle size on total erosion-corrosion, and its separate erosion and corrosion components has revealed that for the same addition of particles by weight, the corrosion rate under erosion is independent of the particle size. However, the erosion produced is heavily dependent on the particle size, being approximately constant for large sizes and decreasing rapidly below 100jm. These findings have been corroborated by microscopy of the sample surfaces.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:504877 |
| Date | January 1997 |
| Creators | James, J. S. |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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