Pembangunan sistem pengaktifan hibrid anod korbanan aluminium
Mohd Subhi, Din Yati
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Aluminium through minimal preparation and modification, applicable for a wide range of applications in electronics, aerospace and chemical industries. In this study, works were conducted toward the potential of aluminium in marine applications by developing aluminium sacrificial anode with hybrid activation system. The main problem faced by aluminium is a tendency to passivate due to the formation of protective oxide layer on 86 the surface. In this study, a metal tin (Sn) and ruthenium (Ru) was used due to its potential as an activation agent for dimensional stable anodes (DSA) used in the production of chloride with a record of more than 30 years with 10 year of life span. While Sn has been used as grain refiners and activator agent for aluminium alloys. Casting methods used for the fabrication of Al-Zn-Mg alloys with addition of Sn until exceeding it solids solubility factor in aluminium matrix (α-Al) which causes it to react with Mg to form Mg2Sn intermetallic compounds. This is achieved by adding of more than 1.0%wt. of Sn element. The presence of Mg2Sn has increased the electrochemical performance of A-4 (Sn=1.46%wt.) alloy specimen and later be used as a substrate for the subsequent studies. The potential of A-4 alloy specimen were further enhanced through the used of deposited Ru. It’s ability as an activator were electrochemically tested while its physical appearance were monitored through observation and analysis of its morphology and topographical aspects. Through Impedance Electrochemical Spectroscopy (EIS) analysis, substrate with 8000ppm deposited Ru has managed to decreased the surface polarization resistence Rp from 3240 Ω.cm2 (A-4) to 152 Ω.cm2 (B-3) after 10 hours immersion in seawater. Small Rp value indicates the easiness of alloy to decompose when exposed to electrolyte. B-3 alloy performance improved by heat treatment through thermal firing process at a temperature of 400o103 C for a period of 30, 60, 90, 120 and 150 minutes. As a result, alloys undergo thermal firing process of 30 minutes has giving the highest corrosion rates of 244 μm/years with a current density of 178 μm/cm2 compared to 240 μm/years corrosion rates and 158 μA/cm2 106 current density by B-3 alloy. Through all the improvement made, the efficiency of the alloy was increased from 82.95% (A-4) to 89.65% (B-3) and finally 91.76% (C-1). This was also bourne out by the topographical characteristic of deposited RuO2 on the aluminium =alloy surface that led to uniform corrosion attacks. This is also shown by the decreased of surface roughness Rsa from 98.031 μm to 56.993 μm and finally 44.632 μm for specimen A-4, B-3 and C-1. Deposited RuO2 has been promoting the formation of surface with macro and micro crack to help the migration of Al+3 ions to facilitate alloy dissolution reaction. Through the distinctive capabilities of both Sn and deposited RuO2,the performance and efficiency of developed aluminium alloy has been successfully enhanced when used in sea water.