Aluminium Alloy 3003 is essentially commercially pure aluminium with the addition of manganese. It is the most popular general-purpose alloy and has good formability and weldability properties. The essential microstructural features that influence the mechanical properties of aluminium are: grain structure, constituent phase particles, precipitations and crystallographic texture. The aim of this project is to study the influence of magnesium on the mechanical properties of the Aluminium Alloy 3003, now considered as AA-9031, after addition of magnesium, using an offline processing route. The study was done on two Alloy 9031 with varying amounts of magnesium content (0.20 wt.% and 0.22 wt.%). The supplied slabs were thermo-mechanically processed simulating an industrial process route used for the sheet production of Alloy 3003 for automotive single-clad products. The effect of magnesium on the mechanical properties was studied through microstructure analysis, hardness, yield and tensile strength. The difference of 0.02% magnesium content between the two alloys showed no significant differences in the mechanical and microstructural properties. The hardness, yield strength and ultimate tensile strength were found to be similar. The difference in mechanical properties was so insignificant that one can regard this difference as a standard deviation. An annealing time of 2 h at both 285 ℃ and 380 ℃ was not adequate to obtain a fully recrystallized microstructure.