Mechanical Properties and Corrosion Behaviour of Extruded and Welded AA6082

Abstract

Welding and corrosion will play a key role in the further increased use of aluminium alloys in industrial applications. This is especially true as the oil and gas industry is moving into the arctic region in search for new oil and gas reservoirs. The effect on corrosion of the low temperatures that will be encountered in this region must be understood. In this study, six extruded and welded AA6082-T6 flat bars with thicknesses ranging from 10 to 30 mm have been subjected to material characterization, an accelerated intergranular corrosion (IGC) test, recording of polarization curves in artificial seawater at high and low temperatures and measurements of open circuit potential (OCP) at high and low temperatures.The results from this study show that the extent and weakening of the heat affected zone (HAZ) will not change as the thickness is increased up to 30 mm. Moreover, the HAZ in the examined profiles will not be more susceptible to IGC and pitting corrosion than the base material. It is therefore recommended that the standards on aluminium structures, like EN 1999-1-1[1], include welded aluminium profiles up to 30 mm, as compared to the maximum thickness of 15 mm at present time. Results also show that the corrosion behaviour at low ocean temperatures will be superior compared to higher temperatures. This is shown by the raising of the pitting potential, corrosion potential and OCP at low temperatures, in addition to a lowering of the cathodic limiting current.