The relationship between corrosion rate of aluminum (AA 5083) and supply electric voltage in seawater

In this paper effect of electric voltage level on corrosion rate of Aluminum (AA 5083) was studied. Eighty samples plate surfaces were prepared according to the standard procedure. The corrosion studies have been carried out at room temperature using seawater. Various level of electric DC voltage (0, 1.5, 3 and 4.5 V) applied and samples were left for 10, 20, 30 and 40 days in order to determine its corrosion rate for each and every level of voltages supplied. These samples were analyzed to determine the weight loss, electrochemical test using Electrochemical Impedance Spectroscopy and morphology test to determine the corrosion rate of the Aluminium plate and effect of voltage levels. After 40 days, the final weights of all samples were differed compare to the initial weights. For 0 V sample initial and final weights were4.7375 g and 4.7164 g respectively, which is 99.7% of its initial weight. For 1.5 V sample, initial weight was 4.7262 g and final weight was 3.8833 g, which is 82.4% of its initial weight. Meanwhile, for samples of 3 V and 4.5 V, initial weights were 4.7225 g and 4.7511 g respectively, after 40 days; samples were loosed 1.3025 g and 1.5169 g respectively. The results reviled that electric voltage is one of the factor that can accelerate corrosion of Aluminium AA 5083 in seawater. Further, results indicated that introduction of electric voltage obviously maximize weight losses and enhance Aluminium dissolution in seawater. As a conclusion from this study, corrosion rate of Aluminium AA 5083 plate is increasing by increasing of DC electric voltage in seawater. 2013 Trade Science Inc. - INDI

The effect of Arc voltage and welding current on mechanical and micro structure properties of 5083-Aluminium Alloy joints used in marine applications

The aluminium and its alloys are widely used in marine applications such as ship hull and its components due to its lightweight and corrosion resistance. The aluminium alloys require special tool and skill to weld due to high thermal conductivity. A research vessel “RV Discovery” is currently being constructed exclusively using 5083-aluminium alloy for University Malaysia Terengganu and the welding properties were investigated. The aluminium welded joint specimens were prepared using the Metal Inert Gas (MIG) welding process by certified welders at different current and voltage settings. The mechanical characteristics of the welded alloys were carried out for tensile and hardness tests. Further, metallographic examination was conducted to identify and observe the various fusion zones. The results of these tests are presented in this paper. This study revealed that, the different welding voltage and current settings in which specimens were prepared remarkably affect the mechanical properties of 5083-aluminium alloy joints

Techno-economic study of Aluminium alloy and steel as materials for deckhouses of offshore support vessels

Aluminium alloy is a relatively more expensive material than steel although its weight is one-third of the steel. Thus the use of steel as a structure adds additional weight by 60%; and when used as deckhouses would raise the GM and scarifying the stability of the offshore support vessel. This paper reviews the merit and demerit of Aluminium alloy and steel focusing on fabrication and assembly, and maintainability cost typical of a 60.0m offshore support vessel operating between Kemaman port and offshore oil rigs in the South China Sea. Mathematical equation was used to calculate the weight of the materials used to construct the deckhouses. Also, net present value and payback period calculations were performed to indicate the economic benefit between the two materials. The initial construction cost for Aluminium and Steel are USD 45506 and USD 6808 respectively involving 23.5 metric ton for Aluminium and 67.0 metric tons for steel. In term of investment, offshore support vessels using Aluminium have shorter payback period of 7.9 years and 8.4 years for steel inclusive of the costs of maintenance and operation. This exercise indicates Aluminium alloy is more economical than steel as construction material for deckhouse of offshore support vessel due to its light weight, lower maintenance and increase earning capacity (more cargo)

Comparison of Aluminium alloy and steel materials as deckhouses for offshore support vessels

Aluminium alloy is a relatively more expensive material than steel although its weight is one-third of the steel. Thus the use of steel as a structure adds additional weight by 60%. This paper reviews the merit and demerit of Aluminium alloy and steel focusing on fabrication and assembly, and maintainability cost typical of a 60.0m offshore support vessel operating between Kemaman port and offshore oil rigs in the South China Sea. Mathematical equation was used to calculate the weight of the materials used to construct the deckhouses. Also, net present value and payback period calculations were performed to indicate the economic benefit between the two materials. The initial deckhouse construction cost for Aluminium and Steel are USD 45507 and USD 26808 respectively involving 23.5 metric ton for Aluminium and 67.0 metric tons for steel. In term of investment, offshore support vessels using Aluminium have shorter payback period of 7.9 years and 8.4 years for steel inclusive of the costs of maintenance and operation. This exercise indicates Aluminium alloy is more economical than steel as construction material for deckhouse of offshore support vessel due to its light weight, lower maintenance and increase earning capacity (more cargo)

Prediction of maneuvering behavior of an offshore supply vessel by using simulation program

Manoeuvring ability of Offshore Supply Vessel (OSV) is a very critical aspect. An early prediction of vessel behaviour will definitely help to improve upon the design. The regular methods available for manoeuvring prediction such as free running model test, captive model test etc., are found to be expensive and time consuming. As an alternative, the current approach tries a numerical simulation method with parameters determined from a database. This study presents the manoeuvring prediction of an OSV which includes the development of time domain simulation program by using Matlab Simulink software. Three degrees of freedom were considered and applying the Newtonian laws, the equations of motion were framed. Further, forces on hull, forces and moments induced by propeller and rudder were also taken into reckoning. Results were obtained with inputs of vessel speeds, engine revolutions etc. Validation of the prediction results was also carried out by comparing the results with full-scale sea trial data. The prediction results show a good agreement with the sea trial data. Applying approximate numerical formula for manoeuvring prediction is seen to be a reliable and economic prediction tool at early design stages of such vessels