Inhibition of mild steel corrosion using carica papaya and bitter-leaf extracts in 1.5M H2SO4 environment.
Date
2024-07
Authors
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Journal ISSN
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Publisher
Federal University of Technology,Owerri
Abstract
This work concerns the corrosion inhibition of mild steel in 1.5M H2SO4 solution with and without the addition of plant-leaf extracts of Vernonia amygdalina (VA) and Carica papaya (CP). The inhibitor was obtained by filtering the juice from the ground fresh leaves of VA and CP. Weight loss technique was employed in the corrosion study while phytochemical analyses were conducted on the examined plant leaves to unravel the bioactive constituents. The duration of exposure time of specimens in the study environment spanned for 24, 48, 72, 96, and 120 hours. The concentrations of the inhibitors were added at 5ml, 10ml, 15ml, and 20ml respectively. On the other hand, the inhibitor concentrations of the synergetic admixture (SA) were added such that CP or VA had the constant concentration (2ml) and remaining concentrations were augmented by the other at 5mL (2ml + 3ml), 10mL (2ml + 8ml), 15mL (2ml + 13ml), and 20mL (2ml + 18ml) respectively. Results revealed that the corrosion of mild steel in a 1.5 M H2SO4 solution was inhibited by the addition of both Vernonia amygdalina and papaya leaf extracts. As the VA leaf extract concentration was raised, the corrosion rate reduced, with the maximum inhibition efficacy of 64.8% being attained with 20 mL of VA after 24 hours. However, from 24 to 120 hours, a gradual decline in the inhibitor's potency was observed, which suggests that 20 mL concentration of VA does not offer a tenacious covering of the mild steel in 1.5 M H2SO4 for a longer period. The inclusion of Carica papaya leaf extract prevented mild steel from corroding in 1.5M H2SO4. After 48 hours, 20 mL of CP leaf extract produced the maximum inhibitory efficacy of about 86.89%. When Vernonia amygdalina and Carica papaya leaf extracts were combined, they demonstrated superior corrosion inhibition when compared to VA alone. The mixture of 18 mL of VA and 2 mL of CP showed the greatest degree of inhibitory effectiveness. Comparing Vernonia amygdalina to Carica papaya leaf extract, the latter appeared to be more successful in preventing corrosion in 1.5 M H2SO4 due to better inhibitory efficiency. The phytochemical analyses of the examined leaves revealed the presence of tannin, phytate, phenol, hydrogen cyanide, and alkaloid. To predict the observed corrosion rates, multiple regression (MR) and artificial neural network (ANN) models were applied. In general, ANN predictions had less errors than MR predictions, indicating that ANN is better at predicting nonlinear corrosion inhibition relationships.
Description
Master of engineering thesis on "inhibition of mild steel corrosion"
Keywords
Corrosion inhibition, vernonia amygdalina, carica papaya, leaf-extract, artificial neural network, multiple regression, materials and metallurgical engineering.
Citation
Nwadike, C. O. M. (2024). Inhibition of mild steel corrosion using carica papaya and bitter-leaf extracts in 1.5M H2SO4 environment. (Unpublished Master's Thesis), Federal University of Technology, Owerri