A COMPARATIVE STUDY BETWEEN DIFFERENT CORROSION PROTECTION LAYERS

The purpose of this paper was to compare carbon-steel electrodes treated with alumina and porphyrin and electrodes treated with phosphogyps and porphyrin. For coating the electrodes we used a mixture of granular materials (alumina and phosphogyps), porphyrin dissolved in benzonitrile and paint alkyd-melamine enamel.[1] We applied the improved method of dipping the electrode in paint before and after passing through the granular material. Initially we used three types of granular materials as corrosion inhibitors: silicon carbide, alumina and phosphogyps, but we concluded that silicon carbide is not a good corrosion inhibitor. Alumina is produced from bauxite in the well-established Bayer process. The Bayer process is the principal industrial means of refining bauxite to produce alumina. Bauxite, the most important ore of aluminum, contains only 30-54% alumina, Al2O3, the rest being a mixture of silica, various iron oxides, and titanium dioxide. Phosphogyps is a waste product resulted from the process of obtaining the phosphoric acid from apathy and phosphorite by extraction with sulphuric acid.[2,3]. Porphyrins may be combined with other materials, including known coating materials, compositions, or precursors of such materials. We tested two types of modified porphyrins: Na4TFP Ac - dissolved in KOH (10%) and H2SO4 (10 %) and H2TPP - dissolved in benzonitrile. The morphological structure characterization of the alumina and phosphogyps were analysed through SEM (Inspect S + EDAX GENESIS XM 2i) and X-ray diffraction. The efficiency of the complex multifunctional system as a corrosion inhibitor was investigated in the salt spray chamber for 14 days with an exposure zone temperature of 35°C. The test involves 24 hour repetitive cycles: 5 minute spray and 55 minutes dry off. The corrosion resistance was studied on coated carbon-steel electrodes with the salt spray chamber (DCTC 600). Cyclic voltammetry (VOLTALAB 80, Universal Potentiostate PGZ402) was used for the electrochemical measurements of three different porphyrin systems in the electrolyte solution Na2SO4 20%. In conclusion we can say that from the three types of granular materials, the silicon carbide had the lowest resistance, followed by the alumina and highest resistance was that of the phosphogyps. References: [1] Rahimi, A., Inorganic and Organometallic Polymers:A Review, Iranian Polymer Journal 13 (2), 149-164, 2004; [2] C. Badea – Contribu?ii privind reutilizarea de?eurilor refolosibile pentru producerea unor noi tipuri de construc?ii, Tez? de doctorat, Timi?oara, 2004; [3] Harris, Chris; McLachlan, R. (Rosalie); Clark, Colin – Micro reform — impacts on firms: aluminium case study. Melbourne: Industry Commission, 1998.

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