An electric current is passed through the interface of liquid gallium and aqueous electrolyte in a square cross-section cell under a background vertical magnetic field. The oscillation increment of surface waves is calculated from potential measurements at variable current strengths. The surface is also visually observed through transparent side walls. No growing surface waves occur for the Sele parameter as high as 1.5. Instead, a quasi-static surface deformation is caused by the rotation of the metal and electrolyte. The maximum height of this surface deformation increases approximately in proportion to the current. Figs 7, Refs 15.