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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 50634 (07)
- University: Sharif University of Technology
- Department: Materials Science and Engineering
- Advisor(s): Ghorbani, Mohammad
- Abstract:
- In this study, the magnetite protective oxide layer was successfully formed on carbon steel substrate in an alkaline solution by an electrochemical method. The electroblackening was performed at a constant potential of 2 volts and in a 50 wt% solution at 75 ° C for 10 minutes. The properties of coating characterized using X-ray diffraction, field emission-scanning electron microscopy, polarization test and visible light spectrophotometery and porosity and thickness of oxide coating investigated. By adding 50 grams per liter of each of nitrate and chromate oxidizers, the porosity of oxide coating decreased from 24 percent to 14 percent and coating thickness increased from 1 micron to 3 microns. The reflection of oxide layer in visible region is about 1%. The electrochemical blackening reduced the corrosion current density of substrate about 50% and increased the corrosion potential about 100 mV in a 3.5% NaCl solution, and Sealing process with polyester transparent lacquer increased the substrate corrosion resistance from 3 hours to 400 hours in salt spray test. It was found that the advantages of electrochemical blackening of steel against chemical blackening is reduction of process temperature (from 140 to 70 ° C), reduction of the process time (from 30 minutes to 10 minutes), the reduction of temperature hazards, reduction reflection in visible light and in similar properties
- Keywords:
- Steels ; Atmospheric Corrosion ; Surface Oxide Layer ; Optical Absorption ; Electrochemical Method ; Electroblackening
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