Some five membered heterocyclic compounds were synthesized by the reaction of 2,4-thiazolidinedione or 5,5-diphenylhydantoin potassium salts with 2-chloro-N-alkylacetamides and alkyl-2-chloroacetates. The structure confirmations of the synthesized compounds were performed by FT-IR, H-1 NMR, C-13 NMR spectra. The inhibitory effectiveness of the compounds were evaluated against the corrosion of steel strip immersed in water containing paraffin based mineral oil medium in accordance to standard test method. Surface characterization studies of the metal coupons used were performed by SEM analysis and also by the contact angle measurements using the Sessile-Drop method. In addition the 3D image of the metal surface was obtained using optical profilometer. The test results and surface characterization studies showed that all synthesized compounds are excellent corrosion inhibitors in such a water in oil emulsion system. (C) 2012 Elsevier B.V. All rights reserved.