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).
Mild steel protection in acidic media using Mucuna pruriens seed extract
The inhibition of corrosion of mild steel in 1 molar hydrochloric acid solution (1 M HCl) by Mucuna pruriens seed extract (MPSE) was investigated by weight-loss and electrochemical techniques. A significant decrease in the corrosion rate of mild steel was observed in the presence of the investigated additive and the inhibition efficiency was found to depend on the concentration of the MPSE. The potentiodynamic polarization data indicated that this additive was of mixed type, but the anodic effect was more pronounced. Nyquist plots showed that on increasing the MPSE concentration, the charge transfer resistance increased and double layer capacitance decreased. The thermodynamic parameters of adsorption revealed a strong interaction between the MPSE constituents and the corroding metal surface. MPSE lowered the corrosion reaction by blocking the mild steel surface through chemical adsorption. The mechanism of inhibition was discussed in the light of the chemical structure of the four major components of MPSE.
Effect of 1-Hydroxyethylidene-1, 1-Diphosphonic Acid on the Corrosion of SS 41 Steel in 0.3% Sodium Chloride Solution
Abstract The effectiveness of 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP) as a corrosion inhibitor was investigated by measuring corrosion weight losses and polarization curves of SS 41 steel in 0.3% NaCl. In concentrations lower than 50 ppm of HEDP, the corrosion of SS 41 steel was inhibited in accordance with the Langmuir adsorption isotherm of HEDP on the steel. The adsorption was believed to be a chemical adsorption resulting from the value of adsorption heat. In concentrations greater than 50 ppm of HEDP, the iron complex of HEDP developed, and the inhibition effect was decreased. Instead, it caused rust to be removed from the steel surface. The mutual inhibition effect by adding both HEDP and the Zn2+ ion in 0.3% NaCl solution was progressively more increased. It was shown that HEDP does not easily decompose.