In this research, the 6082-T651 aluminum alloy with constant rotating speed and various welding speeds were utilized using a friction stir method with two different types of square pins and a triangular pin welding. The purpose of this research is to investigate the effect of the welding speed and tools geometry in the microstructure and mechanical properties, and then the effect of thermal treatment on mechanical properties and abnormal grain growth and corrosion of the joints. For this purpose, the bobbin friction stir welding with the parameters including constant rotational speed 1400rpm and various welding speeds in the range of 20 to 112 mm/min was done. The samples were then subjected to post thermal treatment of solution at a temperature of 530? for one hour and aging at 190? temperature for six hours. The microstructure of the welded specimens were studied and characterized using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and phase analysis X-ray diffraction. Mechanical properties were investigated using a single-axis tensile test and microhardness in width of the welded section. In order to investigate the corrosion behavior, immersion test was done in 3.5% sodium chloride solution and polarization test was done in 3.5% sodium chloride solution with a pH number of to 6 and 1.5. In order to investigate the failure from the environment and resistance to stress corrosion cracking, a tensile test with slow strain rate was used in sodium chloride solution 3.5% with a pH number of 1.5. The results showed that with increasing welding speed, tensile strength increases initially and reduces dramatically after the occurrence of volume defects. The maximum strength was obtained using square pins and at 90 mm/min equal to 198.75MPa. Microstructural observations showed that with increasing welding speed, the grain size decreases in the stir zone. The pattern of hardness was symmetric. it was obtained along the thickness, which shows that the joints have homogeneous mechanical properties along the thickness. Microstructural observations after heat treatment showed that increasing the welding speeds from 20 to 112mm/min reduced the sensitivity of the structure in the stir zone to the abnormal grain growth And grown grains that exceed 95% of the stir zone, reduces to less than 24%. According to mechanical properties, post weld heat treatment increases the tensile strength and hardness and decreases the elongation, which causes the weakest region in the welding zone to be transferred from the HAZ to the SZ. The results of corrosion tests showed that the highest corrosion current density was related to the heat affected zone and the thermomecanical affected zone and stir zone have better corrosion resistance. The corrosion of the corroded areas in all three zones includes uniform corrosion with pitting corrosion. The results of a slow strain rate tests showed that in the welded samples, environment sensitivity was observed and the cracks caused by the environment occurred at the boundary between the TMAZ/SZ. Elongation percentages in SSRT indicate that the base alloy is softer than the welded specimens, in sodium chloride solution3.5%. Investigation of the cross section fracture in the base metal test sample showed that the surfaces fracture had dimples that shown ductile breakdown in aluminum, but in the welded specimens, cleavage fracture was also observed.