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Please use this identifier to cite or link to this item: http://bsuir.bsum.edu.ng:8080/jspui/handle/11409/579

Title: EFFICACY OF ACIDIMETRY AS A CORROSION MONITORING TECHNIQUE IN DETERMINING THE KINETICS AND THERMODYNAMICS OF CORROSION INHIBITION BY L-LEUCINE, ASPARTIC ACID AND Sareocephalus Latifolius
Authors: GBERTYO, JOSEPH AONDOAVER
Keywords: ACIDIMETRY, KINETICS
THERMODYNAMICS, CORROSION, L-LEUCINE, ASPARTIC ACID
Issue Date: May-2019
Publisher: NONE
Citation: NONE
Abstract: Many corrosion monitoring techniques are available to corrosion and material scientists. However, the choice of a particular technique that will be least expensive and readily available with minimal error has been a challenge. In this work, the efficacy of acidimetry as a corrosion monitoring technique was evaluated with two other established methods; weight loss measurement and electrochemical impedance spectrophotometry (EIS). The study was conducted at a temperature range of 301 K to 313 K, using L-leucine, aspartic acid and Sarcocephalus latifolius as inhibitors after screening a number of several potential compounds and plant extracts for their efficiency. The inhibition efficiency and surface coverage of the selected inhibitors followed a similar trend; increasing with increase in concentration and temperature, which is a feature of chemical adsorption. At each studied temperature, Sarcocephalus latifolius had the highest inhibition efficiency with its highest value of 83.67 % at 313 K. The scanning electron micrographs of the metals inhibited by Sarcocephalus latifolius showed a better adsorption of the inhibitor on the iron surface incorporating into the passive film. Values of free energy of adsorption, ∆Gads were all negative for all the inhibitors, which means the adsorption processes were spontaneous, and below -20 kJmol-1, suggesting physical adsorption. Conversely, the increase in parameter b value of the AEI model for the inhibitors with rise in temperature upheld the processes to be chemical adsorption. The heats of adsorption, Qads values were all positive, implying that the processes required absorption of heat from the surrounding. Activation energies for all the concentrations and temperatures were within the range of 10.49 kJmol-1 and 49.97 kJmol-1. The fairly constant value of activation energy is also a confirmation of chemical adsorption mechanism. The negative sign in the values of entropy of adsorption, ∆Sads confirmed that the activated complex in the rate-determining step was associative. The data obtained was tested with several isotherms and they best fitted the El-Awady, Freundlich and Tempkin adsorption isotherm models. The efficiency of the inhibition process for the three techniques are in the order EIS>acidimetry>weight loss. Based on the fact that acidimetry has been observed to be close to EIS, the technique can be recommended for use in corrosion monitoring.
URI: http://bsuir.bsum.edu.ng:8080/jspui/handle/11409/579
Appears in Collections:Chemistry

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