A series of metal-phosphonate organic-inorganic polymeric hybrid materials are synthesized, structurally characterized, and evaluated for their anticorrosion properties for the protection of carbon steels. These materials are Zn-AMP (where AMP = amino-tris(methylenephosphonate)), Zn-HDTMP (where HDTMP = hexamethylenediamine-tetrakis(methylenephosphonate)), and Ca-PBTC (where PBTC) 2-phosphonobutane-1,2,4- tricarboxylate)). Their structures are described and compared. Their corrosion inhibition performances are also compared, and some interesting conclusions are drawn that relate molecular structure to inhibitory activity.