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The Effect of Inhibitors on the Corrosion of Automotive Aluminum in Water and Ethylene Glycol Environment

Asadikia, Mohammad | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 39685 (57)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad
  7. Abstract:
  8. In this study, the effects of different corrosion inhibitors on the corrosion of aluminum alloy which is used in the cooling systems of automotive industries were investigated. Also a comparison between the corrosion behaviour of the mentioned aluminum alloy with and without any galvanic connection to 5 different metals consist of solder, stainless steel, mild steel, brass and copper was done. The corrosion rate became more by establishing galvanic coupling. The base solution was ethylene glycol and water which is the base part of all antifreeze compounds. The tests were done at high temperature about 88ºC. Two different industrial corrosion inhibitors were examined in these conditions. Potentiodynamic polarization test, mass loss test, surface chemical analysis and surface microscopic analysis were the methods which used in this study. For the aluminum samples without galvanic connection, all four used inhibitors produced passive layer on the metal surface. For the aluminum samples with galvanic connection, chromate, diphosphate, molibdate, nitrite and silicate could passivate the aluminum surface. Although sodium silicate had better action in reduction of corrosion rate, but signs of pitting could be seen on the sample. In the compound corrosion inhibitors group, two solutions one containing nitrite, molibdate and chromate and the other containing nitrate, tetraborate, bicarbonate and chromate showed the best function in controlling the corrosion of aluminum by the efficiency based on aluminum of %94.9 and %92.1 respectively. These compounds acted better than the two industrial corrosion inhibitors which the better one's efficiency was %6.6. In this part, again all of solutions containing sodium silicate caused severe pitting on the aluminum surface. By comparing of these results, useful compounds were found which are compatible with ethylene glycol and can control the corrosion of aluminum in these conditions very well. The corrosion rate of aluminum in solution number 15 was 0.367 mpy, in solution number 18 was 0.122 mpy and in the industrial inhibitor A was 4.29 mpy
  9. Keywords:
  10. Ethylen Glycol ; Corrosion ; Aluminum Alloy ; Corrosion Inhibitors ; Automotive Corrosion ; Antifreeze

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