Electrochemical studies of mild steel corrosion inhibition in sulfuric acid chloride by aniline

Experimental and Theoretical Studies on the Corrosion Inhibition of Carbon Steel by Two Indazole Derivatives in HCl Medium

In this work, two indazole derivatives, namely 5-aminoindazole (AIA) and 5-nitroindazole (NIA), were investigated as corrosion inhibitors for carbon steel in 1 M HCl solution by experimental and density functional theory (DFT) methods. The electrochemical results indicate that the inhibition ability follows the order of AIA > NIA, which is due to the stronger electron-donating effect of -NH2 of the AIA group than the -NO2 group of NIA. Besides, the frontier orbital theory shows that the AIA exhibits higher reaction activity than NIA, and a more negative adsorption energy for AIA was also obtained, which is consistent with the analysis of the electrochemical measurements. We draw the conclusion that the electron-donating effect makes it easier for AIA to donate electrons to iron atoms to form a stronger protective layer than NIA.

Electrochemical analysis of the corrosion inhibition properties of L-leucine and trypsin complex admixture on high carbon steel in 1 M H2SO4 solution

Se evaluó la inhibición de la corrosión por parte de compuestos químicos biodegradables (complejo de L-leucina y tripsina) sobre acero de alto contenido de carbono en H2SO4 1 M a través de técnica de polarización potenciodinámica, análisis de pérdida de peso, medición de potencial de circuito abierto, microscopía óptica y espectroscopia ATR-FTIR. Los datos obtenidos mostraron que la mezcla tiene una eficacia de inhibición máxima de 82,4% y 90,08%, a partir de las pruebas electroquímicas con propiedades de inhibición de tipo mixto. La adición de la mezcla cambia significativamente el potencial de corrosión del acero a los valores de pasivación de la medición del potencial de circuito abierto. Los resultados de los cálculos termodinámicos indicaron un mecanismo de adsorción por quimisorción de acuerdo con las isotermas Langmuir, Freundlich y Frumkin, acopladas con coeficientes de correlación de 0,9994; 0,9651 y 0,8834, respectivamente. El análisis estadístico mostró que el tiempo de exposición es la variable más importante en la inhibición de la corrosión. Los grupos funcionales de la mezcla, identificados mediante espectroscopía ATF-FTIR, fueron completamente adsorbidos en la superficie de acero al carbono; esto se dedujo a partir de la observación de la disminución de la intensidad de pico. Las imágenes de microscopía óptica de las superficies de acero inhibidas y desinhibidas contrastan entre sí, debido a la presencia de macro-pozos y óxido poroso en el acero desinhibido.

Cymbopogon citratus and NaNO2 Behaviours in 3.5% NaCl-Immersed Steel-Reinforced Concrete: Implications for Eco-Friendly Corrosion Inhibitor Applications for Steel in Concrete

This paper studies behaviours of Cymbopogon citratus leaf-extract and NaNO2, used as equal-mass admixture models, in 3.5% NaCl-immersed steel-reinforced concrete by nondestructive electrochemical methods and by compressive-strength improvement/reduction effects. Corrosion-rate, corrosion-current, and corrosion-potential constitute electrochemical test-techniques while compressive-strength effect investigations followed ASTM C29 and ASTM C33, in experiments using positive-controls for the electrochemical and compressive-strength studies. Analyses of the different electrochemical test-results mostly portrayed agreements on reinforcing-steel anticorrosion effects by the concentrations of natural plant and of chemical admixtures in the saline/marine simulating-environment and in the distilled H2O (electrochemical positive control) of steel-reinforced concrete immersions. These indicated that little amount (0.0833% cement for concrete-mixing) of Cymbopogon citratus leaf-extract was required for optimal inhibition efficiency, η = 99.35%, on reinforcing-steel corrosion, in the study. Results of compressive-strength change factor also indicated that the 0.0833% Cymbopogon citratus concentration outperformed NaNO2 admixture concentrations also in compressive-strength improvement effects on the NaCl-immersed steel-reinforced concrete. These established implications, from the study, on the suitability of the eco-friendly Cymbopogon citratus leaf-extract for replacing the also highly effective NaNO2 inhibitor of steel-in-concrete corrosion in concrete designed for the saline/marine service-environment.