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Title:	Pembangunan lapisan fe-al (aluminide) bagi perlindungan kakisan
Authors:	Hishamuddin Husain (P41520)
Supervisor:	Abdul Razak B. Daud, Prof. Dr.
Keywords:	Lapisan fe-al (aluminide) Kakisan Corrosion and anti-corrosives
Issue Date:	11-Aug-2014
Description:	Keluli karbon rendah adalah bahan struktur yang penting dalam industri tetapi ia mudah terkakis di dalam berbagai persekitaran. Ini disebabkan oleh sisik besi oksida yang terbentuk pada permukaannya kurang padat dan mudah bertindak balas redoks dengan kehadiran O2 atau H2O. Oleh itu satu lapisan pelindung yang mantap perlu diwujudkan pada permukaan keluli ini supaya ia dapat menghalang kakisan terutamanya di dalam persekitaran mengkakis atau pengoksidaan yang kuat seperti persekitaran berair yang mengandungi oksigen dan klorida. Kajian ini dijalankan bagi menghasilkan lapisan aluminium oksida dan lapisan antara logam Fe-Al (Aluminide) pada keluli karbon rendah sebagai sawar pelindung daripada serangan kakisan. Lapisan nipis aluminium oksida dan lapisan antara logam dihasilkan dengan mencelup keluli karbon di dalam leburan aluminium dan diikuti dengan pemanasan suhu tinggi di dalam persekitaran udara menggunakan relau. Celupan panas di dalam leburan aluminium tulen dilakukan pada suhu 720, 750 dan 780oC dengan tempoh celupan selama lima hingga 30 minit. Ketebalan salutan aluminum dan lapisan antara logam Al-Fe didapati meningkat dengan tempoh celupan. Ketebalan salutan aluminum mencapai 62.3μm untuk 5 minit celupan dan meningkat kepada 381.0μm untuk 30 minit celupan. Ketebalan purata lapisan antara logam pula sekitar 82μm bagi tempoh celupan 5 minit dan meningkat kepada kira-kira 207μm untuk tempoh celupan 30 minit. Pengoksidaan terhadap salutan aluminum telah dilakukan melalui pemanasan pada suhu 600 hingga 900oC untuk tempoh satu jam di dalam persekitaran udara. Didapati suhu dan tempoh pemanasan mempengaruhi taburan fasa, kekerasan dan ketebalan lapisan antara logam. Fasa antara logam yang dikesan adalah Fe2Al5, FeAl3 dan FeAl. Nilai kekerasan hasil pencelupan panas menunjukkan penurunan akibat pemanasan pengoksidaan. Kewujudan aluminium oksida dikesan menggunakan spektroskopi fotoelektronsinar-X (XPS) dan analisis sinar-X sebaran tenaga (EDX). Pertumbuhan lapisan aluminium oksida pada sampel yang dipanaskan dikaji berdasarkan pertambahan berat. Nilai punca ganda dua min Rq bagi kekasaran permukaan ditentukan dengan mikroskop daya atom (AFM). Rq meningkat dengan suhu pemanasan dan mencapai sekitar 300nm bagi pemanasan pada suhu 700oC. Peratus kadar keporosan lapisan aluminium oksida didapati menurun apabila suhu pemanasan ditingkatkan dan menyebabkan rintangan kakisan dan juga impedans bagi sampel di dalam larutan 3.5% NaCl meningkat. Bagi sampel yang dipanaskan pada suhu 700 dan 900oC, kadar kakisannya di dalam larutan 3.5%NaCl masing-masing adalah 56.82 dan 21.97µm per tahun manakala impedans masing-masing pula ialah 2161 dan 2288 Ohm.cm2. Sebagai kesimpulan kajian ini menunjukkan yang lapisan nipis aluminium oksida dan lapisan antara logam Fe-Al (Aluminide) telah berjaya dihasilkan pada keluli karbon rendah yang dapat melindungi keluli berkenaan daripada kakisan dengan berkesan.,Low carbon steels are important structural materials in industry but they are corroded easily in many environments. This is due to the iron oxide scale formed on their surface is less compact and easily causing redox reaction in presence of O2 or H2O. Therefore a steady protective layer should be provided to the surface of the steels to protect them from corrosion especially in corrosive or harsh oxidising environments such as aqueous environments containing oxygen and chlorides. This study was conducted to form a thin aluminium oxide and Fe-Al (Aluminide) intermetallic layer on low carbon steel as a protective barrier from corrosion attack. The aluminium oxide and aluminide were produced by immersing the carbon steel in molten aluminium and followed by high temperature heating in air environment using a furnace. Hot-dipping in molten pure aluminium was carried out at temperatures of 720, 750 and 780oC for five to 30 minutes.The thickness of aluminium coating and intermetallic layer of Al-Fe was found to increase with dipping time duration. The aluminium coating thickness reached 62.3μm for five minutes dipping and increased to 381.0μm after 30 minutes dipping. The average thickness of the intermetallic layer was about 82μm for five minutes dipping and increased to about 207μm for 30 minutes dipping. Oxidation of aluminum which was coated on the sample surface was performed by heating at 600 to 900oC for one hour in air environment. It was found that temperature and heating time influenced phase distribution, hardness and thickness of intermetallics. The intermetallic phases determined by both hot dipping and oxidation heating are Fe2Al5, FeAl3 and FeAl. As a whole, it is acknowledged that the hardness value from hot dipping declines due to oxidation heating. The presence of aluminum oxide was investigated using X-ray photoelectron spectroscopy (XPS) and Energy dispersive X-ray analysis (EDX). The growth of aluminum oxide layer on the heated samples was investigated based on weight increase.The root mean square valueRqfor surface roughness was determined by Atomic Force Microscopy (AFM). Rq increased with heating temperature and achieved a value of about 300nm for heating temperature of 700oC. Porosity rate of the aluminium oxide layer decreased when the heating temperature was increased which resulted in the increase of corrosion resistance as well as impedences of the samples in 3.5% NaCl solution.For samples heated at 700 and 900oC, their corrosion rates in 3.5% NaCl solution were 56.82 and 21.97µm per year whereas their impedances were 2161 and 2288 Ohm.cm2 respectively. In conclusion, this study has shown that a thin aluminum oxide and Fe-Al intermetallic (Aluminide) layers have successfully been formed on low carbon steel which was able to protect the steel from corrosion effectively.,PhD
Pages:	151
Call Number:	TA467.H538 2014 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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