Corrosion Behaviour of Aluminium Alloy 7020-T6 welded Joint in Sea Water at Different Variables


were welded by using inert gas metal arc welding method (MIG)to obtain butt jointwith geometry of single V at 45⁰with two pass.The joints were tested by X-ray radiography and faulty pieces were excluded.andthe indefectible joints were subjected to stress relief heat treatment including heatingthe joint to evaluating temperature 100 C⁰for one hour and air cooling.Opticalmicroscopy with camera was used to observe the welded joint microstructure.Microhardness test were carried out using Vickers instrument to measure the hardness of thewelded joint.Corrosion behavior of welded jointspecimens in 3.5% NaCl solution at differentmedia velocity (1, 2, 3) m/min and temperature of (25, 50, 75) ⁰ C for each velocitywasexamined using Tafelpolarization measurements. It is determined byopen circuitpotential (OCP) after that the cell’s current is changed due to the increasing inpotentialby ±100mV to calculate corrosion current then corrosion rate.The results show that the corrosion rate is increased with increasing solutiontemperature. This is because of the prevention of oxygen from dissolving in water,while the corrosion rate decreases with increasing velocity of sea water since themovement of the liquid prevents the formation of deposits and ions gathering oncathode pole where corrosion can easily develop.when comparing corrosion rate between the welded and unwelded samples, thewelded samples gives more corrosion rate value since the cycle of heating and coolingthat occurs during the welding process affects the microstructure of welds.