علی عرب زاده

In the present study, the corrosion behavior of projection friction stir spot welding of 2024 aluminum alloy has been investigated and compared with the corrosion behavior of the base metal. Welding of sample was performed with the rotation speed of 2500 rpm and the dwell time of 12 seconds. The penetration depth of the tool on the surface of the sample was 0.1 mm, the diameter of the tool was 16 mm, and a circular protrusion with a diameter of 10 mm and a height of 0.4 mm was placed below the working table. By using Tafel polarization test method and standard Scanning Kelvin Probe through potential chang of weld surfaces and base metal as well as chang in corrosion current density, the corrosion behavior of projection friction stir spot welding was investigated. The results showed that the corrosion potential of the weld area is reduced compared to the base metal, although this reduction has not led to a significant increase in corrosion current density. Also, the welding zone has higher corrosion current density than the base metal region.

In order to determine a suitable alternative welding method for substituation of fusion and resistance welding in oil and gas industry, a new method of projection friction stir spot welding with constant diameter and depth of protrusion is herein used for welding of 2024 aluminum sheets. By studying the previous research that was done on the friction stir spot welding of this material, the rotational speed of 800rpm is chosen for this purpose.For this purpose, the microstructure along with corrosion behavior of projection friction stir spot welding of Al2024 joints is investigated as a novel welding technique in oil and gas sector which produces reliable, safe, smooth and keyhole-free joints. The microstructural changes of different welding areas are studied by novel field emission scanning electron microscopy and consequently the hardness profiles of different areas is drawn. The effect of corrosive oil solution containing salts on welded specimens is studied and various types of pitting and intergranular corrosion are observed in different welding areas. Eventually, accumulation of corrosion products are observed in the stirred area of the weld and the TMAZ shows the highest rate of intergranular corrosion.