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).
The inhibition of 4-(2′-amino-5′-methylphenylazo) antipyrine on corrosion of mild steel in HCl solution
Abstract The effect of 4-(2′-amino-5′-methylphenylazo) antipyrine (AMPA) on the corrosion of mild steel in a 2 M HCl solution was studied using weight loss and potentiodynamic polarization techniques. All of the data reveal that AMPA acts as an inhibitor in the acid environment; furthermore, polarization data show that the compound behaves as a mixed-type inhibitor. It was found that the inhibition efficiency increases with an increase in AMPA concentration but decreases with an increase in temperature. Flory–Huggins adsorption isotherm and El Awady thermodynamic–kinetic model fit the experimental data of the studied compound. Thermodynamic parameters for corrosion and adsorption processes were obtained from experimental data of the temperature studies.
Effect of Metallic Cations on the Corrosion and the Hydrogen Absorption by Cold-Rolled Mild Steel in Inhibited Sulfuric Acid
Abstract The effect of metallic cations, such as Cu++, Hg++, and Ce++++ on the corrosion rate and hydrogen absorption by cold-rolled mild steel in 2N H2SO4, containing thiourea and allylthiourea at 30 C has been studied systematically. Individual metallic cations inhibit corrosion and hydrogen absorption by the steel considerably. Low ppm cation additions increase hydrogen absorption. The % inhibition efficiency of thiourea and allylthiourea increases, and the hydrogen absorption by the steel decreases, with individual increases in Cu++, Hg++, and Ce++++ concentrations. In presence of inhibitors and at lower concentrations of metallic cations, the electrode potential shifts toward electronegative values, and at higher concentrations of metallic cations or metallic cations in association with the inhibitors, the potential is found to shift toward the electropositive side. The results have been discussed in light of the adsorption theory.