Cationic resins based on epoxy resins which are modified through the introduction of phosphoric acid segments and the process of producing the resins are described. The reaction of the phosphoric acid is carried out in a multiple-step process whereby, in a first step, the diester is formed through reaction of ortho-phosphoric acid with 2 moles of a monoepoxy compound or through reaction of a polyphosphoric acid with n-1 moles of a monoalcohol and subsequent reaction with n+1 moles of a monoepoxy compound. The remaining acid group is reacted with a di- or polyepoxy resin. The products obtained can still contain unreacted epoxy groups. The protonable groups are introduced via the epoxy groups and/or via the hydroxy groups present or set free by opening of the oxirane ring. The binders can be combined with hardening components or may be formulated as self-crosslinking binders. The binders have excellent resistance to corrosion when stoved as electrodeposited coatings.