An electromagnetic pump comprising a housing having a fluid receiving chamber (14) in communication with an inlet (18), a fluid pumping chamber (16) in fluid communication with an outlet (20), a check valve operatively associated with the fluid receiving chamber, and a barrier in the form of a thin diaphragm hermetically isolating the electromagnet from the fluid chambers. An armature of the pump includes both a pole portion located for magnetic attraction by the electromagnet and a piston portion to force fluid out of the chambers. The armature pole portion has a fluid-contacting section of material which is compatible with and corrosion resistant to the fluid. A controlled bypass (274) is provided for bubbles in the fluid. An outlet orifice (290) and accumulator (436) are provided in the path of fluid flow from the pump outlet.