Corrosion Of Mild Steel Research Articles

Investigation of mild steel corrosion inhibition in acidic media by Viola extract based on bulk and nanometer size

In the present work, the inhibition performance of Viola extract based on bulk and nano size as a green corrosion inhibitor on mild steel in 0.5 M phosphoric acid and 1M hydrochloric acid solutions is investigated using different techniques (potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Optical microscopy). The gained results demonstrated that various concentrations of Viola Extract (bulk and nano) inhibited the corrosion of the alloy in both of the acid solutions. The temperature impact on corrosion rate without/with this extract was examined. Certain thermodynamic parameters were determined based on the temperature impact on inhibition and corrosion processes. The adsorption mechanism of the extract on the alloy was explored using the Langmuir adsorption isotherm. A mixed mode of adsorption was observed, wherein the nano-sized extract in 1.0 M HCl predominantly underwent chemisorption, while the bulk-sized extract in 1.0 M HCl and both bulk and nano-sized extracts in 0.5 M H3PO4 were primarily subjected to physisorption. Scanning electron microscopy (SEM) and Optical microscopy analyses were employed to scrutinize alloys’ surface morphology.

Facile synthesis, corrosion inhibition, adsorption and DFT studies of 2-(4-(methylsulfanyl) phenyl) −4, 5-diphenyl-1H-imidazole for mild steel in acidic environment

A green, solvent-free, cost effective one-pot synthesis method is employed to produce the innovative corrosion-inhibiting compound 2-(4-(methylsulfanyl)phenyl)-4,5-diphenyl-1H-imidazole (MDPI). The molecular structure of MDPI can be identified using CHN analyses, FT-IR, 1H and 13C NMR spectra. Various electrochemical and gravimetric techniques are utilized to evaluate the anti-corrosion properties of MDPI. The results indicate that MDPI effectively inhibits the corrosion of mild steel under all tested conditions. At 306 K, MDPI achieved a maximum corrosion inhibition efficiency of 98.01 % at a concentration of 10 mM. MDPI exhibited strong adsorption and excellent anti-corrosion properties, forming a protective layer on the mild steel surface. The Langmuir adsorption isotherm, with a ΔGoads value of −39.55 kJ/M was found to be more suitable for this study, indicating that the process occurred by physisorption. Tafel curves indicated that MDPI functions as a mixed-type corrosion inhibitor. Surface characteristics were analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). Quantum chemistry studies revealed a HOMO-LUMO energy gap of 3.926 eV, corroborating the anti-corrosion effectiveness of MDPI in hydrochloric acid solution. MDPI exhibited promising anti-corrosion activity due to its heterocyclic ring containing nitrogen heteroatoms as well as a methylsulfanyl functional group.

Experimental, electrochemical and DFT simulation studies of a novel Schiff base derivative as an efficient mild steel corrosion inhibitor in acidic environments

A newly synthesized Schiff base, consisting 3-methyl-2-{(E)-[(2E)-3-phenylprop-2-en-1-ylidene] amino} butanoic acid, is utilized to prevent mild steel from corroding in acidic environments. FTIR spectra validate the prepared SB. The corrosion rate at various temperatures was measured using electrochemical techniques like as polarization and electrochemical impedance tests. At a higher temperature of 333K, this molecule exhibits about 90% inhibition efficacy with 50 ppm inhibitor. The corrosion inhibition mechanism was measured using thermodynamic and adsorption characteristics. These findings suggest that chemical adsorption causes a surface layer to form on the metal surface. The Langmuir adsorption isotherm is followed. The creation of the adsorption layer on the metal surface is confirmed by SEM and AFM pictures. Quantum chemical calculations were calculated and discussed.

Protection of mild steel from corrosion in HCl solution via green Rumex acetosella extract: Experimental and theoretical studies

The efficiency and potential of green Rumex acetosella extract (RAE) on the inhibition of the mild steel (MS) corrosion were investigated in the acidic environment. The high inhibitive capability of RAE on the mild steel was studied by electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. In addition, potentiodynamic (PD) polarization measurements were carried out to examine corrosion mechanism. The achieved electrochemical tests showed that RAE has a significant inhibition effect on mild steel corrosion. The results of surface analysis recorded by scanning electron microscopy (SEM), and atomic force microscopy (AFM) depicted that RAE provide strong protective layer on the steel surface via adsorptive groups. The inhibition efficiency was calculated as 99.7 %, and 99.6 % from LPR and EIS after 120 h exposure time. Adsorption free energy (∆Gadso) value is found as −29.79 kJ mol−1, indicating that both physical and chemical adsorptions occur. Furthermore, the obtained experimental findings were supported with quantum chemical calculation results.

Comprehensive Investigation of the Adsorption, Corrosion Inhibitory Properties, and Quantum Calculations for 2-(2,4,5-Trimethoxybenzylidene) Hydrazine Carbothioamide in Mitigating Corrosion of XC38 Carbon Steel under HCl Environment.

This study investigates the inhibitory effects of 2-(2,4,5-trimethoxy benzylidene) hydrazine carbothioamide (TMBHCA) on the corrosion of carbon steel in a 1 M HCl solution across various concentrations. The assessment employs a comprehensive approach, combining gravimetric analysis, potentiodynamic polarization tests, and electrochemical impedance spectroscopy (EIS). Additionally, scanning electron microscopy (SEM) and quantum chemical calculations are employed to provide a thorough understanding of the corrosion inhibition mechanism. The influence of exposure time on mild steel corrosion is systematically examined. Results reveal a remarkable reduction in the corrosion rate of steel, with TMBHCA demonstrating its highest inhibition efficiency of 97.8% at 200 ppm. Potentiodynamic polarization studies characterize TMBHCA as a mixed-type inhibitor, while Nyquist plots illustrate increased charge transfer resistance and decreased double-layer capacitance with escalating TMBHCA concentrations. Consistency between weight loss measurements and electrochemical findings further validates the efficacy of TMBHCA as a corrosion inhibitor. SEM images substantiate and visually support the obtained results. An immersion test conducted at 25 °C over 28 days showcases a notable enhancement in TMBHCA efficiency (IE%) from 45.16% to 92.43% at 200 ppm as the immersion period progresses from 1 day to 28 days. This improvement is attributed to the augmented adsorption of inhibitor molecules on the steel surface over time. These comprehensive findings significantly contribute to our understanding of TMBHCA's corrosion inhibition behavior, emphasizing its potential as a highly efficient corrosion inhibitor for diverse industrial applications.

Corrosion inhibitive performance of Kopsia teoi extracts towards mild steel in 0.5 M HCl solution

This study investigates the capacity of Kopsia teoi (K. teoi) to inhibit corrosion, employing its stem extracts to prevent mild steel (MS) corrosion in 0.5 M HCl. In this study, three distinct extracts: dichloromethane alkaloid (KTDAE), dichloromethane non-alkaloid (KTDNAE), and methanol (KTME) were employed to investigate their corrosion mitigation performance, involving electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) techniques. EIS results demonstrated a significant increase in inhibition efficiency with concentration for each extract, reaching 87.04, 90.62, and 93.51 % for KTDAE, KTDNAE, and KTME, respectively. According to PD analysis, Kopsia teoi extracts (KTEs) functioned as mixed-type inhibitors. Surface analysis through scanning electron microscopy-energy dispersive X-ray spectroscopy exhibited notable improvements in the morphology of treated MS plates, revealing the establishment of a protective surface film. Langmuir isotherm confirmed that KTEs formed a monolayer on MS surface, and the calculated free energies of adsorption were −25.924, −26.809, and −27.687 kJ mol−1 for KTDAE, KTDNAE, and KTME, respectively. This suggests effective adsorption through both physisorption and chemisorption mechanisms. Consequently, the results of this study highlight the encouraging effectiveness of KTEs as corrosion inhibitors for MS in acidic environments.

Methanol extract of Murraya koenigii stem as green inhibitor for mild steel corrosion in 1 M HCl solution

In this work, methanol extract of Murraya koeginii stem has been studied as an ecofriendly inhibitor against mild steel corrosion in 1 M hydrochloric acid medium. Ultraviolet–visible and Fourier transform infrared spectroscopic tools were employed to characterize the extract. Corrosion inhibition efficacy of the extract against mild steel was studied in terms of weight loss method and electrochemical measurement method. Weight loss measurement shows the inhibition efficiency of 94.95 % for the first 6 h of immersion time and maximum efficiency of 96.39 % for 24 h immersion time using 1000 ppm inhibitor solution. Electrochemical measurement shows that for the same concentration of inhibitor, inhibition efficiency is 81.54 % in as-immersed condition whereas it is 85.76 % in 1 h immersed condition. Free energy of the adsorption reflected the physisorption followed by chemisorption. Similarly, thermodynamic parameters revealed the feasibility and spontaneity of the adsorption. Obtained results showed that the methanol extract of Murraya koeginii stem can be a potential corrosion inhibitor.

Insights of newly synthesized novel pyrazole compounds for mild steel corrosion inhibition in an acidic environment by experimental and computational calculations

Pyrazole derivative Ethyl (E)-2-cyano-3-(1,3-diphenyl-1H-pyrazol-4-yl)acrylate (Pz-a) and its novel nitro derivative Ethyl (E)-2-cyano-3-(3-(3-nitrophenyl)-1-phenyl-1H-pyrazol-4-yl)acrylate (Pz-b) were synthesized and characterised using Mass spectra, IR, 1H NMR, 13C NMR and utilized to safeguard mild steel from degradation in 1 M Hydrochloric acid environment. The inhibition effectiveness and mechanism were examined through both experimental and theoretical calculations. Electrochemical analysis illustrate that the protective property of pyrazoles rises proportionally with concentration. Potentiodynamic polarization reveals, both pyrazoles exhibit characteristics of mixed type inhibitors, inhibiting both oxidation and reduction processes. Pz-a and Pz-b adhesion on mild steel surface resembles the Langmuir isotherm. Gibbs free energy of adsorption (ΔGads) indicates Pz-a and Pz-b adsorbs physically and chemically over metal surface. The inhibition efficiency was found to be 89.85 % for Pz-b and 84.47 % for Pz-a at 10−2 M concentration. AFM scanning further confirms that the inhibitors are confined over mild steel. Better understanding of the corrosion inhibition mechanism has been facilitated by theoretical investigations through DFT parameters.

Investigation of the Adsorption Characteristics of <i>Theobroma cacao</i> Peels Biomass Inhibitors on Mild Steel Surfaces by EIS, SEM-EDX, XPS, and Chemical Studies in Acidic Media

Investigators used Potentiodynamic Polarization, Spectroscopy of Electrochemical Impedance (EIS), Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX), Spectroscopy of X-Ray Photoelectron (XPS), and chemical studies to examine the inhibitory effect of Theobroma cacao peel extract (TCPE) on mild steel (MS) corrosion in 1.5M HCl. Studies of electrochemical data indicate that, TCPE reduces MS corrosion through adsorption using a mixed inhibition mechanism. As the inhibitor concentration grows and temperatures lowers, TCPE becomes more protective. The adsorption of TCPE molecules on the MS surface is controlled by the Langmuir adsorption isotherm. To determine the correlation between the hampers effect and the structure of TCPE molecular, a number of chemical characteristics were computed.

Computational and experimental investigation of anticorrosive potential of Panthenol for mild steel in 1 M hydrochloric acid solution

An investigation into how Panthenol affects the corrosion of mild steel in 1 M hydrochloric acid was carried out, specifically its adsorption behaviour and the mechanism by which it inhibited corrosion and for this electrochemical analysis techniques, weight loss, scanning electron microscopy, atomic force microscopy, contact angle measurements has been used. Also, the theoretical study which includes study of global reactivity descriptors EHOMO, ELUMO, energy gap (∆E) etc. and molecular dynamics (MD) simulations in aqueous phase have been used to simulate the real situation. This study confirmed a high inhibition efficacy of 90 % at a concentration of 400 ppm. The electrochemical analysis demonstrated that as the concentration of Panthenol increased, there was an apparent reduction in the value of jcorr and an upsurge in the value of Rct. In case of potentiodynamic polarization, the value of jcorr came out to be 144 μA cm−2 and in electrochemical impedance spectroscopy, the value of Rct came out to be 125.32 Ω cm2 at 400 ppm. The surface morphological investigations revealed the deposition of an extensively protective coating on the mild steel surface. Calculated values of roughness (average and root mean square in nm) in the present study shows a reduction in roughness (in the acid the values were 401 nm, 518 nm respectively and acid with Panthenol, the values were 56.9 nm and 82.5 nm, respectively). In quantum chemical calculations, the calculated value of ΔE came out to be 5.098, validating the strong tendency of inhibitor to retard the corrosion. The investigation revealed that Panthenol is an effective and environmentally friendly inhibiting agent of corrosion for mild steel in a 1 M HCl solution. Additionally, the theoretical findings reiterated the experimental results obtained in this study.

Kopsia terengganensis’ alkaloids as potential green inhibitors for mild steel corrosion in CO2-saturated 3.5% NaCl medium

The corrosion inhibition potential of alkaloids from Kopsia terengganensis bark extract (KTBE) in mitigating the mild steel corrosion in a CO2-saturated 3.5% NaCl medium was evaluated. Standard corrosion evaluation methods, including weight loss test, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PD) were employed, which revealing a concentration-dependent enhancement in KTBE's inhibition efficiency. At 500 ppm, the corrosion inhibition efficiency recorded the highest value of 90.63% based on the weight loss study and 87.38% based on electrochemical analysis. Tafel slopes in PD studies affirmed that KTBE functioned as an anodic-type inhibitor. The adsorption of the inhibitor is in accordance with the Langmuir adsorption isotherm with an adsorption free energy (ΔG°ads) of −26.47 kJ/mol, suggesting the binding of KTBE molecules by means of physisorption. Surface analysis conducted through scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, and Fourier transform infrared spectroscopy (FTIR) confirmed the formation of a protective inhibitive layer on the surface of mild steel. The proposed corrosion inhibition mechanism involves electrostatic interactions between KTBE molecules and the mild steel surface. This comprehensive investigation underscores KTBE's potential as an effective corrosion inhibitor in corrosive environments.

Insights into the high and prolonged inhibition mechanism of pyridoxine hydrochloride as vitamin B6: a new green inhibitor slowing the acidic corrosion of mild steel

Insights into the high and prolonged inhibition mechanism of pyridoxine hydrochloride as vitamin B6: a new green inhibitor slowing the acidic corrosion of mild steel

Development of anti-corrosive layer on steel alloy using novel synthesized 8-hydroxyquinoline-based inhibitors: Experimental and theoretical approach

New and generated from freshly synthesized 8-hydroxyquinoline derivatives, namely 6-chloro-3-((8-hydroxyquinolin-5-yl)methyl)benzo[d]oxazol-2(3H)-one (Q-Cl) and 3-((8-hydroxyquinolin-5-yl)methyl)-6-nitrobenzo[d]oxazol-2(3H)-one (Q-NO2), were identified and characterized by 13C and 1H NMR spectroscopy. After this, their ability to prevent mild steel corrosion in 1.0 M HCl were examined and evaluated by electrochemical testing and surface analyses coupled with density functional theory (DFT), and density functional based tight-binding (DFTB). It is found that these substances act as the efficient defending agents and their protection increase with their concentrations and depend on their molecular structures. The best inhibition efficiencies values are about 93.59 % and 90.92 % at 10−3 M Q-NO2 and Q-Cl, respectively. Furthermore, the effect of temperature solution indicated that the 8-hydroxyquinolin derivatives take their performance of 298–328 K. In addition, the calculated activation and thermodynamic parameters indicated that they interact with the metallic surface by the chemical adsorption supported by surface analysis result using SEM/EDX analysis. These findings were explained by the Langmuir adsorption isotherm approach, indicating the formation of a monolayer by the 8-hydroxyquinoline derivatives particle on the mild steel surface. Finally, the theoretical investigations DFT/DFTB demonstrate the interaction of the site of the 8-hydroxyquinoline derivatives particles with the mild steel surface to form a protective layer.

Adsorption studies of isoxazole derivatives as corrosion inhibitors for mild steel in 1M HCl solution: DFT studies and molecular dynamics simulation.

The corrosion of mild steel is a significant issue in various industries, prompting the need for effective corrosion inhibitors. This study focuses on understanding the corrosion inhibition properties of organic compounds derived from isoxazole, namely series Iso(a), Iso(b), Iso(c), Iso(d), Iso(e), Iso(f), Iso(g), and Iso(h), which could have implications for materials science and industrial applications. By investigating the influence of different substitutions on these compounds, valuable insights can be gained into designing better corrosion inhibitors for practical use. Theoretical studies were conducted using density functional theory (DFT) with the B3LYP functional and the 6-31G (d,p) basis set. These calculations enabled the evaluation of various parameters including frontier orbital energies (EHOMO, ELUMO), energy gap (∆E), electronegativity (χ), absolute hardness (η), softness (σ), fraction of transferred electrons (∆N), as well as local properties such as natural atomic populations and Fukui indices. Additionally, molecular dynamics simulations were performed to study the adsorption behavior of the inhibitors on the surface of Fe (110). The simulations were conducted using Materials Studio version 8.0 software package using COMPASS force field to understand the impact of different functional groups on the inhibitors before and after adsorption on the iron surface.

RECENT INNOVATIONS IN ORGANIC INHIBITORS FOR MILD STEEL IN CORROSIVE SOLUTIONS: A MINI REVIEW

Corrosion of mild steel in corrosive solutions is one of the major concerns in industries such as oil and gas, petrochemical and marine. The use of organic inhibitors has proven to be an effective method to protect mild steel from corrosion. This mini-review summarised recent innovations in organic inhibitors for mild steel in corrosive solutions. This article discusses the types of organic inhibitors, including adsorption, film-forming, mixed, synergistic and green inhibitors, their mechanism of action, and their application in various corrosive environments. The article then highlights recently published inhibitors such as quinoline derivatives, Schiff bases, amino acids, and polymers. These inhibitors have shown promising results in protecting mild steel from corrosion. The mini-review concludes by discussing the prospects of organic inhibitors for mild steel in corrosive solutions. Overall, this mini-review provides valuable insights into recent innovations in organic inhibitors for mild steel in corrosive solutions, which are useful for researchers and industries working on corrosion protection.

Evaluation of adsorption behaviour of benzylidene chitosan derivatives at mild steel/ 0.5 M H2SO4 solution interface

Four green benzylidene chitosan derivatives (BCs) were synthesized and evaluated as anti-corrosive substances for the first time against mild steel corrosion in 0.5 M H2SO4 solution. The synthesized BCs were laid to infrared spectroscopy and proton resonance spectroscopy for structural confirmation. Gravimetric and electrochemical experiments were accustomed to appraise the effectiveness of inhibitors, however, Scanning Electron Microscopy-Electron Dispersive Spectroscopy (SEM-EDS), Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy (XPS) were exploited to evaluate the protective mechanism offered by benzylidene chitosan derivatives. Experimental results demarcate the synthesized inhibitors; Anisaldehyde modified Chitosan (CMB), 2-Hydroxy-4-methoxybenzaldehyde modified Chitosan (CHMB), 2,4-Dimethoxybenzaldehyde modified Chitosan (CDMB) and 2-Bromo-4-methoxybenzaldehyde modified Chitosan (CBMB) exhibiting praising inhibitory properties for mild steel corrosion and CDMB was seen possessed preferable inhibition potential at the finest concentration of 500 mgL-1 owing to the proximity of two electron-donating OCH3 groups. Furthermore, the inhibitors have been recorded to behave mixed type with pronounced impact on hydrogen evolution kinetics. The order of inhibition efficacy obtained was CDMB (98.8 %) > CHMB (95.4 %) > CMB (92.8 %) > CBMB (89.2 %) which was further validated by quantum chemical calculations which later opened up about the mechanistic approach involved in electron transfer from inhibitors to metallic vacant orbitals. Additionally, the effect of molecular structure possessed by synthesized inhibitors has been correlated with observed variation in their corrosion inhibition efficiency.

Polyethyleneglycol bisphenol A epichlorohydrin copolymer (PEG-BEC) as a highly efficient inhibitor for mild steel corrosion in 1M HCl solutions

In this work, the corrosion inhibition performance of polyethyleneglycol bisphenol A epichlorohydrin copolymer (PEG-BEC) against mild steel in 1 M HCl was studied by electrochemical and weight loss techniques. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX) were applied to characterize the surface morphology of the mild steel samples. The corrosion mitigation efficiency was observed to rise as the concentration of PEG-BEC rises in the corrosive medium while increasing the temperature (25 °C -65 °C) resulting in a drop in the inhibition ability. Furthermore, under hydrodynamic conditions, the corrosion of the mild steel was found to deteriorate both in the absence and presence of PEG-BEC. Just with 10 ppm, an inhibition efficiency (IE) of 97.6% was obtained at 25 °C by EIS. PEG-BEC acts as a mixed-type inhibitor as observed by potentiodynamic polarization (PDP) technique. The observed corrosion inhibition action of PEG-BEC could be ascribed to the adsorption of the molecules and the formation of a protective film on the steel surface as evidenced by static water contact angle (WCA). Langmuir isotherm best describes the PEC-BEG-metal adsorption with large Kads values indicating a thermodynamically stable nature inhibition process. The obtained ∆G°ads = -35.138 to -39.522 kJ/mol indicate that the PEG-BEC spontaneously adsorbed onto the steel with strong tendency to provide protection to the mild steel surface via combination of chemisorption and physisorption processes. The ΔHads -53.07 kJ/mol and ΔSads= +0.048 kJ/mol-k, respectively, suggests an exothermic reaction accompanied by relatively increase in entropy of the PEG-BEC adsorption on the mild steel surface.

Corrosion inhibition potential of new oxo-pyrimidine derivative on mild steel in acidic solution: Experimental and theoretical approaches

Through electrochemical impedance testing and potentiodynamic polarisation, it was investigated how a material at ambient temperature might prevent corrosion. 1-(5-(4-Methoxybenzoyl)-4-(4-methoxyphenyl)-2-oxopyrimidin-1(2H)-yl)-3-(4-chlorophenyl) urea (MMOP) was used as a corrosion inhibitor on mild steel samples in 1 M HCl. With a maximum inhibition efficacy of 97.6 % (at immersion period of 72 h and concentration of 5 × 10-4 M), the inhibitor used was shown to be an exceptional corrosion inhibitor. Based on the findings of potentiometric polarization, this substance falls within the category of mixed inhibitors since corrosion inhibition was accomplished by the inhibitor adhering to the metal. Adsorption of investigated MMOP completely followed Langmuir adsorption isotherm and adsorption can be categorized as physisorption–chemisorption, with a value of ΔGads of -35.6 kJ.mol-1. In order to confirm the effectiveness of the protective coating applied to the mild steel surface, we analysed the protective layer through the utilization of Atomic Force Microscopy (AFM) and Scanning Electron Microscope (SEM) / Energy Dispersive X-ray spectrometry (EDX). The density functional theory (DFT) and Monte Carlo simulation (MCS) approaches were used to investigate the relationship between molecular structure and inhibitory efficacy. The results suggest that the inhibitor in issue could be a new approach to reducing mild steel corrosion under harsh circumstances and long immersion times.

Inhibition of Mild Steel Corrosion by New Epoxy Resin in 1 M HCl: Synthesis, Characterization, Experimental Study and Theoretical Approach

Inhibition of Mild Steel Corrosion by New Epoxy Resin in 1 M HCl: Synthesis, Characterization, Experimental Study and Theoretical Approach

Corrosion Protection of Mild Steel in Simulated Offshore Environment Using Ocimum gratissimum Leaf Extract

The inhibitive action of Ocimum gratissimum leaf extracts on mild steel corrosion in 1M HCl and 0.5 NaCl solutions was studied using the Gravimetric technique. Four weighed well-polished coupons suspended into sample bottles labeled 200mg/l, 400mg/l, 800mg/l, 1200mg/l and the blank respectively was used. The results shown in Tables 1 to 5 is the weight loss data of mild steel in 0.1 M HCl and the effects of Ocimum gratissimum introduction and how the mild steel corroded progressively thereby increasing the weight loss value over immersion time as seen in Fig. 1. Fig. 2 shows the effects of Ocimum gratissimum extract concentration on the corrosion rate of mild steel in HCl, it is evident that increase in the concentration of the extract led to the decrease in the value of weight loss leading to appreciable inhibition efficiency. The plot in Fig. 3 showed that the values of the inhibition efficiency increased with the concentration of Ocimum gratissimum extract in the acidic environment except the value for 9 days which decreased with concentration. These results led to decrease in the values of inhibition efficiency over time as shown in Fig. 4. Tables 6 to 10 shows the weight loss data for the corrosion of mild steel in 0.5 M NaCl and the effects of Ocimum gratissimum introduction. The result showed that mild steel corroded, leading to fluctuations in the inhibition efficiency. Figs. 5-8 showed the variations of efficiency with time with different concentrations of Ocimum gratissimum in 0.5 M NaCl. Addition of Ocimum gratissimum extract synergistically increased the efficiency of the inhibitor and helped reduce the corrosion rate. A mechanism of adsorption is proposed to explain inhibition behaviour.