L-Dopa as Corrosion Inhibitor for Mild Steel in Mineral Acid Medium
Corrosion inhibition of mild steel was studied using L-Dopa in aqueous hydrochloric acid and sulphuric acid so- lutions. The corrosion behaviours of the steel specimen in the presence of inhibitor weret studied by galvanostatic polari- zation and weight loss techniques. The measured electrochemical data indicated good inhibition of corrosion in both the corrosive medium in presence of L-DOPA. The corrosion inhibition may be explained on the basis of adsorption and for- mation of surface film of L-DOPA on the metal surface. The surface of the steel specimen subjected to electrochemical corrosion in the presence and absence of the inhibitor was studied using scanning electron microscopic images. In the present investigation, L-DOPA is used as corrosion inhibitor for mild steel in aqueous hydrochloric acid and sulphuric acid solutions. The corrosion inhibition efficiency of the compound is studied by potentiodynamic polarization and weight loss studies. The surface morphology of the metal surface before and after corrosion is studied by SEM images. 2. EXPERIMENTAL Analytical Reagent (AR) grade chemicals (sd. fine chemicals, Mumbai) were used for the study. The aqueous solution of sulphuric acid and hydrochloric acid was used as the corrosive media. L-dopa was used as received and the structure of the L-dopa was used as corrosion inhibitor is as shown in Fig. (1).
Electrochemical behavior of 3,4-dihydroxyphenylalanine in aqueous solution
Abstract The electrochemical oxidation of 3,4-dihydroxyphenylalanine ( l -DOPA) has been studied in various pHs using cyclic voltammetry. In this work, the effects of different parameters such as pH, l -DOPA concentration, time window of the chosen electrochemical method, and temperature on the electrochemical behavior of l -DOPA have been studied for understanding the oxidation mechanism of this compound. The experimental data presented in this work, indicate that the process of electrooxidation of l -DOPA follows an E q C i E q mechanism. The proposed following chemical reaction in E q C i E q mechanism, include a hydroxylation reaction in strong acidic pHs, both dimerization and intramolecular reactions in moderate acidic pHs and an intramolecular reaction in neutral and basic pHs. Also, the result has shown that in neutral and basic pHs, the rate of the intramolecular chemical reaction is more than that in moderate acidic pH.
Preparation of hydrophilic poly(vinyl butyral) hollow fiber membrane via thermally induced phase separation
Abstract Hydrophilic microporous hollow fiber membranes were prepared via thermally induced phase separation (TIPS). Poly(vinyl butyral) (PVB) and three kinds of polyethylene glycols (PEG) with the molecular weight of 200, 400 and 600 were used as polymer and diluents. In all cases, liquid–liquid (L–L) phase separation occurred and asymmetric cellular structures with the smaller pores at the outer surface were obtained. The properties of membranes such as pore size, water permeability, solute rejection and intensity were investigated by changing molecular weight of PEG, concentration of PVB, composition of the bath and air gap distance. The smaller molecular weight of PEG, the more PEG in the bath and the shorter air gap distance resulted in the higher water permeability, the lower solute rejection property and the lower mechanical strength.