: AA 5251 AL alloys sheet with diameter of 3.5 mm was prepared by GTAW process. the alternative current, frecunecy, percent of positive cylce and current were changed. welded samples were avaluated in the term of apparent , mechanical and corrosion properties. depth and width of weded samples in the visual test were measured. cycle corrosion test as a corrosion test and microhardness, shear puch and tensile test as mechanical tests carried out Taguchi methods was used to find optimum parameter and effect of each of them . L9 perpendiculare arrays were utilized to reduce tests number. SEM and optical microscope, X-ray and EDX were used. high percent of magnesume and cast structure of weldment led to produce very coarce pricipitation, these contributed to reduce corrosion properties of weldment rather than the base metal. the percent of positive cylcle and value of current had influece on width and depth ofweldment, respectively. incresing the level of currence an d percent of positive cycle resulted in optimum apparent properties. tangstan diameter had not effet on mechanical properties. optimume shear strength was obtained in average level of current and high level of positive pole. while optimum tensile strength was obtained in high level of current and percent of positive pole. low level of currenct and high percent of frecoency did not have impac on mechanical properties. on the other hand, it had direct effect on optimum microhardness, shear and tensile strength. aslo frecuncy is an important parameter in corrosion properties which high frecuency, low level of current and high percent of positive cycle led to a optimume of corrosion properties. Keyword: Taguchi, mechanical behavior, corrosion behavior, optimization
