Structured composites between MnTa2O6 and porphyrins: Influence of the number of carboxylic groups grafted on porphyrins on the capacity to inhibit corrosion of steel

Abstract

New sandwich type materials based on MnTa₂O₆ and porphyrins mono- and tetra-substituted with –COOH groups, namely: (tetrakis-(4-carboxy-phenyl)-porphyrin and 5-(4-carboxy-phenyl)-10,15,20-tris-phenyl-porphyrin) have been synthesized and studied to assess the importance of its corrosion inhibition ability on with regard to its of steel the number of –COOH anchors. Morphological investigations on thin films have been carried out by atomic force microscopy. The inhibition of corrosion has been evaluated by open circuit potential measurements and potentiodynamic polarization technique with Tafel representation, after drop-casting deposition onto carbon steel in 0.1M HCl media. The inhibition efficiency of the novel sandwich-type materials based on pseudo-binary oxide MnTa₂O₆ and tetrakis-(4-carboxy-phenyl)-porphyrin or 5-(4-carboxy-phenyl)-10,15,20-tris-phenyl-porphyrin is in the range 76-86% for tetra substituted porphyrin and 84-95% for the mono-COOH substituted porphyrin.