Electromagnetic pollution become an issue these last years with growth of electrical and electronic industry. The shielding of electromagnetic fields is one solution to reduce effects of this pollution. This study proposes an Al/Steel/Al sandwich produced by cold roll bonding to shield low frequency magnetic wave in near field. The structure evolution of sandwich composite has been characterized in function of the reduction rate of thickness. The bonding quality of Al/Steel interfaces has been then quantified by Tensile Bond Strength Test. Finally, the magnetic shielding effectiveness of the composite and the initial Al and steel sheets have been evaluated experimentally and numerically. During cold roll bonding, plastic instability has been observed and causes steel necking and fragmentation. A numerical model has been developed to explain its origin. A good bond quality is attained when debonding of Al/Steel interfaces requires the deterioration of the composite. The composite takes both shielding behavior of steel and Al and can shield low frequency. However, steel fragmentation has a negative impact on shielding effectiveness. The optimal condition between shielding and mechanical properties is then obtained for a reduction rate of 62 % where only few fragmentations are observed.