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Modified Silane Thin Films as an Alternative to Chromates for Corrosion Protection of AA2024-T3 Alloy
| Title: | Modified Silane Thin Films as an Alternative to Chromates for Corrosion Protection of AA2024-T3 Alloy |
| Author: | Palanivel, Vignesh Marudhanayagam |
| Description: | The use of organofunctional silanes as a chromate replacement of aluminum aircraft alloys for corrosion protection has been studied in depth. The corrosion protection offered by these silane films is comparable to chromates and in certain cases even better. But the silane films had some striking drawbacks when compared to the chromates. This work aimed at developing a silane film that would mimic every property of the chromate, making it possible to replace them completely. Two different silane systems were selected based on previous work viz., a solvent-based system and a completely water-based system. The thesis has been divided into six chapters. Chapter 1 deals with the introduction to silane coupling agents and their applications on various metals for corrosion protection. The two silane systems a solvent-based system and a completely water-based system has been described based on previous work. Chapter 2 describes how these silane solutions are prepared and how different additions are made to the silane solutions. Chapter 3 focuses on the addition and optimization of nanoparticles to the silane film on AA2024-T3 alloy. This chapter discusses the strengthening of the silane film due to the nanoparticle addition and the effect on the corrosion and mechanical properties of the silane film. These films were also characterized by infra-red spectroscopy and ellipsometry. It was found that loading of a small amount of nanoparticles such as silica into the silane film can strengthen and enhance the ccorrosion protection of silanes on AA2024-T3 alloys. Also it was demonstrated that other nanoparticles like zinc oxide and carbon fibers had a similar effect on the silane film. Chapter 4 focuses on giving the silane film a self-healing or self-repairing property by adding optimum amounts of leachable inhibitors to the silane film which can be released at a controlled rate and protect local defects or scratches. The corrosion measurements were done using DC polarization measurements, salt spray and immersion tests. SEM/EDAX and TOFSIMS were used to explain the corrosion mechanism for the self-healing effect. Chapter 5 discusses how a silane film can be colored without affecting any of its adhesion and corrosion properties. The silane films on metals cannot be detected as they are clear amber liquids. DC polarization and immersion tests were conducted to study the corrosion properties of the colored silane film. Crosscut adhesion tape test and Machu test were carried out to determine the adhesion of the colored silane system to paints. The results indicate that silane films can be colored and that proper selection and concentration of colorants is essential for optimum performance of the silane film. Chapter 6 gives an overall conclusion on modified silane films as potential candidates for replacement of chromates for aircraft aluminum alloys. Recommendations for future work are also suggested. |
| Permanent Link: |
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1066415503
http://hdl.handle.net/2374.OX/10057 |
| Date: | 2003 |
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