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).
An experimental evaluation of inhibiting corrosion effect of phosphate glass on mild steel in acidic solution
The glass inhibitor with 25% P2O5–25% CaO–50% K2O composition was synthesized and its inhibition potential for mild steel in a molar HCl medium has been evaluated experimentally. The inhibition efficiency was predicted through many parameters particularly by weight loss, contact angle measurements, electrochemical, and potentiodynamic polarization analysis. For this purpose, the equivalent circuit model was used for Electrochemical Impedance Spectroscopy (EIS) measurements. The thermodynamic parameters obtained from experimental analysis was used to evaluate the inhibition efficiency variation with temperature. The results were quite interesting and convincible as the increase in inhibition potential was found by increasing phosphate glass concentration and decreasing temperature. In addition, the glass inhibitor was found a mixed inhibitor, affecting both anodic and cathodic corrosion currents and the inhibitor adsorption onto the mild steel surface was followed by Langmuir isotherm. The adsorption phenomenon of glass inhibitor was also confirmed by water contact angle (WCA) measurements.
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.