Decrease In Inhibition Efficiency Research Articles

Corrosion Inhibition by Musa paradisia ca Peel Extract for SS 304 in 1 M Hydrochloric Acid Solution

Objectives: To study the corrosion inhibition of Musa paradisiaca peel (MPP) extract for stainless steel (SS) 304. Method: The corrosion rate of stainless steel was studied by weight loss measurements in a 1 M hydrochloric acid solution at different concentrations of MPP inhibitor and at various temperatures, e.g., 298 K, 303 K, and 308 K. Scanning electron microscopy (SEM) was used to study the morphology of the films created on the stainless steel surface in various immersion media at various immersion times. Both potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) examined inhibition efficiency. Langmuir adsorption isotherm studied inhibitor surface adsorption SS 304. Findings: The corrosion rate and inhibition efficiency depend on the concentration of the inhibitor and the temperature. When there is an increase in the concentration of the inhibitor, inhibition efficiency increases, e.g., at 50 mg/l concentration, 77% inhibition efficiency, and at 200 mg/l concentration, 87% inhibition efficiency at 298 K. When temperature increases, inhibition efficiency decreases, e.g., at 200 mg/l concentration, 87% at 298 K, 85% at 303 K, and 83% at 308 K. Novelty: This article provides an eco-friendly corrosion inhibitor for stainless steel 304. Musa paradisiaca peel extract inhibitor was previously used for iron, mild steel, and carbon steel but was not used for stainless steel 304 in 1 M HCl. Keywords: Corrosion, Stailess stell, Inhibitor, Acid

Arachis hypogaea’s concentration effect on AISI 1020 carbon steel for corrosion protection

The effects of inhibitor concentration on the corrosion rate and inhibition efficiency of AISI 1020 steel in an acidic and alkaline environment were investigated by means of weight loss measurement at an interval of 7 days and 14 days. To carry out this investigation, the Arachis hypogaea hull was extracted and concentrated in various weight percentages. The inhibition efficiency increased with the increased concentrations of AISI 1020 steel that were immersed in acidic and alkaline solution in the absence and presence of varying inhibitor concentrations of Arachis hypogaea hull extracts. The corrosion behavior, including the corrosion rate, is meticulously characterized through the corrosion rate analysis. The results showed that there is an increase in inhibition efficiency with an increase in inhibitor concentration and that there is a decrease in inhibition efficiency with an increase in immersion time. The organic inhibitor (Arachis hypogaea hull) produced the best inhibition efficiency of 96.4% at a 30% concentration. From the result obtained, Arachis hypogaea hull extracts revealed that it is best suited for inhibition of corrosion of mild steel in both acidic and alkaline environments. The goal of this research paper is to develop a comprehensive understanding of the corrosion inhibition and adsorption mechanisms associated with the implementation of the Arachis hypogaea hull as a natural corrosion inhibitor.

Preparation of nanocomposites for corrosion treatment

Nano-copper oxide was prepared by utilizing photolysis method and characteristic by using FT-IR, XRD and SEM; the nano size was about 51 nm, environmental impact (pollution reduction) can be improved by using nanostructure particles in preventing corrosion, and nanocomposites have also proven to be an effective alternative to other hazardous and toxic compounds. The results of the current article indicated that the inhibition efficiency increases with increasing concentration of nano-oxide which is added to methyl orange, curcumin, the corrosion rate (CR), inhibition effectiveness were studied at different temperatures. The results showed an increase corrosion rate and a decrease in inhibition efficiency with increase temperature.
 KEY WORDS: Corrosion, Inhibitors, Copper oxide, Nanocomposites
 Bull. Chem. Soc. Ethiop. 2024, 38(2), 501-509. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i2.17

Effect of organic component (tartrate) addition on cerium nitrate's ability to inhibit corrosion of mild steel in NaCl solution

Cerium tartrate (CeTar), produced in this study by precipitating cerium nitrate with potassium sodium tartrate (KNaTar), was examined as a corrosion inhibitor. Weight loss tests show inhibition efficiency of 71.7 % with Ce(NO3)3 and 88.7 % with CeTar inhibitor for one-month exposure to mild steel in 7 g/L NaCl solution. The inhibition efficiency drops to 28.6 % with the former and remains around 87 % with the latter inhibitor after six months of exposure. Similar results from electrochemical testing indicate that the inhibition efficiency decreases by adding cerium nitrate. Still, the cerium tartrate inhibitor demonstrates a nearly constant inhibition efficiency for up to 30 d, i.e., ≈90 %. Electrochemical impedance spectroscopy (EIS) performed in these cases shows the following results: (i) with cerium nitrate, a film of iron and cerium oxide, which on prolonged exposure diminishes, and (ii) with cerium tartrate, the formation of a bimetallic film (Fe-tartrate-Ce) and a mixture of cerium hydroxide and iron oxide that protects steel for a longer duration. These inferences are based on the analyses of scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDAX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron (XPS), and Raman spectroscopy results.

Evaluation of the Inhibitive Properties of Silver Nanoparticles in Senna occidentalis Root Extract as Corrosion Inhibitor of Mild Steel

The use of nanoparticles as corrosion inhibitors has gained popularity because of its increased corrosion efficiency due to increase surface to volume ratio. Nanoparticles which undergo physisorption/chemisorption to the corrosion metal surface and inhibit the corrosion efficiently also have low toxicity, low cost and easy production. In this research work, weight lost method was applied to study the inhibitive properties of silver nanoparticles (AgNPs) synthesized using Senna occidentalis root extract as environmentally benign corrosion inhibitor of mild steel in 0.5 M H2SO4 medium at 298 K and 308 K. It was observed that the corrosion rate of the steel sample decreases with increase in concentration of the silver nanoparticles but increased with rise in temperature. The highest inhibition efficiency of 65.59% was obtained at 308 K at the concentration of 5 gdm-3 and the least of 10.58% at the concentration of 1 gdm-3 at 308 K. The decrease in inhibition efficiency with rise in temperature is suggestive of physical adsorption mechanism. The surface coverage was observed to increase with increasing concentration of the nanoparticles and decreased with increase in temperature. This could be as a result of physical adsorption mechanism. The evaluated activation energy was found to be higher for the inhibited process than for the uninhibited process. The increase in apparent activation energy in the presence of the nanoparticles denotes physical adsorption mechanism, while the reverse is usually attributed to chemical adsorption. The negative values of heat of adsorption Qads suggest that the adsorption phenomenon is exothermic.

Rosmarinus officinalis extract as eco-friendly corrosion inhibitor for copper in 1 M nitric acid solution: Experimental and theoretical studies

Rosmarinus officinalis extract (ROE) was studied chemically (mass loss, ML), electrochemically impedance spectrometry (EIS), and potentiodynamic polarization (PDP) as a corrosion inhibitor in 1 M nitric acid. According to ML, ROE is effective like a copper preservative in 1 M HNO3 acid solution at R.T by improving inhibitor concentration up to 77 % at 300 ppm and 25 °C. A study was conducted regarding the effect of temperature on copper adsorption, as well as the calculation of adsorption coefficients. Results indicated that physisorption increases with temperature, indicating a decrease in inhibition efficiency (%IE). Langmuir's adsorption model was consistent with the adsorption mechanism. Using the PDP method, the inhibitor accumulated on the copper surface in mixed forms. Moreover, EIS revealed that the value of double-layer capacitance dropped with an increased dose of ROE, while the charge transfer resistance improved. A different approach was taken to the examination of surfaces. Both theoretical studies and practical results were calculated and compared to demonstrate that the results were valid.

Thermodynamic Investigation of Leptadenia Hastata (Yadiya) Leaves Extract on Corrosion Inhibition of Mild Steel in Acidic Media

The inhibiting effect of Leptadenia hastata (Yadiya) leaves extract on corrosion inhibition of mild steel in acidic media was studied by thermo gravimetric techniques. Three temperatures ranging from 313 K – 333 K with interval of 10 ºC were used to study the effect of temperature on corrosion behavior of mild steel. The thermodynamic parameters and the values of free energy of adsorption for investigated extract were calculated and discussed. The results show that inhibition efficiency increases with increasing the inhibitor concentration, which is attributed to the presence of phytocompounds in the extract. On the other hand, the decrease of inhibition efficiency with increase in temperature indicates the adsorption to be chemisorption. The adsorption of the extract on the mild steel surface obeys the Langmuir adsorption isotherm. It was found that the adsorption increases, in the same direction as inhibition efficiency. The results obtained depict the influences of temperature and its effects on corrosion control in acidic medium.

Novel Synthesis of Some N-Hydroxy Phthalimide Derivatives with Investigation of Its Corrosion Inhibition for Carbon Steel in HCl Solution

In the current study, new derivatives were synthesized by reaction of N-hydroxyphthalimide with chloro acetyl chloride in the presence of Et3N as a base to form 1,3-dioxoisoindolin-2-yl 2-chloroacetate (B1), which in turn enters several reactions with different amines where it interacts with primary amines to give 1,3-dioxoisoindolin-2-yl acetate derivatives (B2-B4) in basic medium, in the same way it interacts with these amines but with adding KNCS to form thiourea derivatives (B5-B7). It also reacts with diamines to give bis(azanediyl) derivatives (compounds B8-B10). The prepared derivatives were diagnosed using infrared FTIR and 1HNMR,13CNMR for some derivatives. Compounds B4, B5 and B9 were measured as corrosion inhibitors the inhibition efficiency varied from 85% to 99% and thermodynamic functions, i.e. Gibbs free energy, activation energy, enthalpy, entropy, were calculated for the derivatives at a concentration of (50 ppm) when mixed with carbon steel as additives and exposing the plate to an acidic medium of hydrochloric acid at a concentration of (1M) in different temperatures. The results revealed that as the temperature increases, the inhibition efficiency decreases.

A comprehensive study on the inhibition behaviour of four carboxylate-based corrosion inhibitors focusing on efficiency drop after the optimum concentration for carbon steel in the simulated concrete pore solution

In this research, the inhibition action of four carboxylate derivatives with different numbers of functional carboxylate groups on carbon steel in 0.5 M NaCl simulating concrete pore solution was investigated using electrochemical measurements in conjunction with the XPS technique. Quantum chemical calculations were also applied to discuss the EIS data and the inhibitor's adsorption behaviour. This paper focuses on the inhibitive action of carboxylate derivates after optimal concentration. The results show that after a critical concentration, the corrosion inhibition efficiency drops to lower values, which the reasons for this matter are still uncertain. We suggest that the adsorption process is directly affected by the number of attractive and repulsive intermolecular interactions. At higher concentrations, electrostatic forces cause the local molecular clusters on the surface, which results in an imperfect layer of molecules that is vulnerable to aggressive agents such as chloride ions. Although with increasing the number of carboxylate groups, the corrosion inhibition efficiency decreases by 35%. However, quantitative XPS results reveal no noticeable reduction in the oxide layer thickness, which indicates that localized attacks lead the corrosion.

Corrosion inhibition potentials of Cucurbita polyesteramide urethane on mild steel in hydrochloric acid medium: Experimental and computational studies

Polyesteramide urethane was synthesized from Cucurbita maxima seed oil and characterized via Thermogravimetric analysis, Fourier Transformed Infrared spectroscopy, and Differential Scanning Calorimetry. The inhibiting effect of the synthesized polyesteramide urethane (CPEAU) on mild steel in 1.0 Molar concentrations of HCl was investigated through electrochemical and weight loss measurements. The temperature effect on the corrosion performance of the mild steel with or without CPEAU was studied in the range of 303–333 K. It was found that an increase in temperature led to a decrease in inhibition efficiency. The adsorption of CPEAU molecules on mild steel was spontaneous and the isotherm model which the adsorption obeyed was Langmuir's. It was observed that, the value of activation energy for the uninhibited test solution (35.82 kJ/mol) was discovered to be less than those obtained for the inhibited test solutions at different temperatures (49.91 kJ/mol, 50.49 kJ/mol, 53.78 kJ/mol, 62.78 kJ/mol and 69.89 kJ/mol), that signifying electrostatic interaction (physisorption mechanism) of CPEAU on mild steel. Potentiodynamic polarization investigation signified a mixed-type inhibition mechanism of CPEAU at a lower concentration with predominant cathodic effects at a higher concentration. Quantum chemical descriptors revealed the carboxylic group on CPEAU molecule as the active adsorptive sites through which adsorption occurred on the mild steel surface, and a molecular dynamics simulation showed the adsorption and binding energies of the inhibitor. The experimental and computational results were in good agreement.

The Role of Cassava Leaf Extract as Green Inhibitor for Controlling Corrosion and Scale Problems in Cooling Water Systems

The addition of synthetic corrosion and scale inhibitors in a recirculating cooling water system is a well-known method to defeat corrosion and scale problems. In this work, we utilize the extract from cassava leaf, which is agricultural waste in Thailand as a green inhibitor. Corrosion inhibition efficiency with using cassava leaf extract (CLE) for mild carbon steel was investigated in a simulated cooling water solution under both stagnant and hydrodynamic conditions. A mock-up of a recirculating cooling water system was custom-built to imitate the hydrodynamic conditions used in industry. Effects of CLE concentration (0, 50, 100, 200, 400, 600, and 800 ppm) and temperature (35 °C, 45 °C, and 55 °C) on corrosion inhibition efficiency were investigated. Increasing the CLE concentration increased its inhibition efficiency. In the case of stagnant conditions, the CLE showed a corrosion inhibition efficiency of 97.4% with 800 ppm CLE at 35 °C. The CLE performed as an anodic inhibitor. A decrease in inhibition efficiency was observed when the temperature was increased. For the hydrodynamic conditions with a flow rate of 34 L min−1 at 55 °C, a corrosion inhibition efficiency of 75.7% was seen with 200 ppm CLE. A scale inhibition efficiency of the CLE was investigated at concentrations of 0, 200, 800, and 2000 ppm. A 76.1% CaCO3 scale inhibition efficiency was obtained with 2000 ppm CLE. A change in the CaCO3 morphology due to the adsorption of the CLE inhibited scale formation.

Exploration of furan derivative for application as corrosion inhibitor for mild steel in hydrochloric acid solution: Effect of immersion time and temperature on efficiency

The possibility of using 2-(5-amino-1,3,4-oxadiazol-2-yl)-5-nitrofuran as a corrosion inhibitor for mild steel in hydrochloric acid solution was explore utilizing weight loss complemented with surface characterization through scanning electron microscopy (SEM) techniques. The effect of time and temperature on the inhibition efficiency of 2-(5-amino-1,3,4-oxadiazol-2-yl)-5-nitrofuran was also investigated. Results from weight loss techniques imply that 2-(5-amino-1,3,4-oxadiazol-2-yl)-5-nitrofuran demonstrate significant anticorrosion characteristics toward mild steel dissolution in 1 M hydrochloric acid environment. The 2-(5-amino-1,3,4-oxadiazol-2-yl)-5-nitrofuran showed the highest inhibition efficiency of 79.49% at the highest inhibitor concentration of 0.005 M studied, for the immersion time of 5 h and a temperature of 303 K from gravimetric result. Inhibition efficiency of 2-(5-amino-1,3,4-oxadiazol-2-yl)-5-nitrofuran differs directly with immersion time or temperature. A decrease in inhibition efficiency with an increase in temperature is implied to the physisorption mechanism and may be imputed to increase in the solubility of the precipitated inhibitor molecules on the mild steel surface. The number of adsorbed molecules on mild steel surface decreases regarding the temperature increases which resulted in a deficiency in inhibitive performance. The kinetic studies indicate that the adsorption of tested inhibitor on the surface of mild steel both physical adsorption and chemical adsorption. Surface characteristic findings confirm the presence of 2-(5-amino-1,3,4-oxadiazol-2-yl)-5-nitrofuran on the tested mild steel surface. 2-(5-Amino-1,3,4-oxadiazol-2-yl)-5-nitrofuran follows the Langmuir adsorption isotherm.

Inhibition of Mineralization of Urinary Calcium Phosphate Stones by Sodium Pyrophosphate

To understand the biological importance of sodium pyrophosphate and its applicability as inhibitors in urolithiasis disease, we have studied the inhibition efficiency of sodium pyrophosphate towards the mineralization of urinary stone forming minerals like calcium phosphate, in aqueous as well as urinary medium. An attempt has been made to unfold, tentatively, the mechanism of inhibition by this inhibitor. It was Observational experiment. The Study was Conducted in the chemistry lab of university department of chemistry, B N Mandal University, Madhepura (Bihar) An experimental model was designed by taking the salt forming solutions, the whole operation took about 40-50 min. At the end the contents of beaker were digested in a hot water bath, cooled to room temperature and centrifuged in small volumes. The total centrifugate was collected and Calcium and carbonate content of the centrifugate of calcium carbonate mineralization experiments were determined. Sodium pyrophosphate has a moderate inhibition efficiency towards calcium carbonate mineralization. At 0.05 M concentration, sodium pyrophosphate has a net inhibition of 30 % which is 26.65 % more than that of water (blank). Compared to water the percentage inhibition increased by 795.52%. With decreasing concentrations of sodium pyrophosphate, the inhibition efficiency decreases. At very low concentration (0.01 M) its inhibition is only slightly higher than that of water. In urinary medium sodium pyrophosphate seems to function as a better inhibitor of phosphate mineralization. At 0.05 M concentration, sodium pyrophosphate has a net inhibition of 89.22 % which is 75.36 % more than that of urine. It is observed that sodium pyrophosphate solution, under different concentrations, exhibits moderate to good efficiency of inhibition towards mineralization of urinary stone forming minerals like calcium carbonate in aqueous as well as urinary medium.

A theoretical and experimental study of castor oil-based inhibitor for corrosion inhibition of mild steel in acidic medium at elevated temperatures

The castor oil as a cheap and environmentally friendly source was used to prepare a novel green corrosion inhibitor for mild steel in acidic medium. The poor performance at high temperatures and low biodegradability are two important challenges of corrosion inhibitors that castor oil-based corrosion inhibitor (COCI) is designed to overcome them. The inhibition performance of COCI was evaluated by weight loss, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and polarization techniques. The morphology of MS was examined by field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX) and atomic force microscopy (AFM). Furthermore, a comprehensive computational study was done to clarify the anticorrosive mechanism of COCI by molecular dynamics (MD) simulation, density functional based tight-binding (DFTB) approach and density functional theory (DFT). Maximum inhibition efficiency of 85 % and 91 % were achieved at 80 °C using 140 μM of COCI in EIS and polarization tests, respectively. COCI acted as a mixed type inhibitor and the adsorption of the inhibitor on the mild steel surface was chemisorption. The obtained results demonstrate that the COCI has a considerable ability to suppress acidic corrosion at all concentrations were studied here, particularly at high temperatures. Given the fact that several articles were reported a significant reduction in performance of corrosion inhibitors by increasing temperature, in this study was found out not only was there no decrease in inhibition efficiency of COCI at higher temperatures, but it depicted good performance at 80 °C. In addition, the high adsorption energy of COCI confirmed a strong interaction between Fe surface and inhibitor molecules and showed a significant effect of the urethane bonds and the triglyceride groups on molecular activity. The Fermi energy state indicated that the chemical adsorption occurred in the interaction of COCI-Fe surface by electron transition from inhibitor to Fe 3d band state. We expect the results of this work provide new opportunities for the design and synthesis of efficient corrosion inhibitors based on vegetable oils.

Green corrosion inhibitor: A comparative study

A comparative study of the inhibitory effect of various parts of the plant Mimusaps Elangi (ME) extract (leaves, fruits, barks, seeds) on the corrosion of mild steel in 1 N HCl medium was investigated using weight loss method, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The polarization studies revealed that the plants extract act as mixed type inhibitor. It was found from the weight loss method that the inhibition efficiency of ME extracts increase in concentration dependents manner which was also supported by the results of electrochemical techniques. On comparison, maximum inhibition efficiency was found in ME leaves extracts with 98.50% at 20 ppm concentration. The SEM morphology of the adsorbed protective film on the mild steel surface has confirmed the high performance of inhibitive effect of the plant extract. Surface coverage values were tested graphically for suitable adsorption. Temperature studies revealed decrease in inhibition efficiency with increase temperature which suggests physisorption mechanism.

Effect of Inhibitor Concentration and Immersion Time on the Corrosion Rate and Inhibition Efficiency of AISI 1019 Steel in Inhibited Seawater Environment

The effect of inhibitor concentration and immersion time on the corrosion rate and inhibition efficiency of AISI 1019 steel in seawater environment were investigated by means of weight loss measurement (WLM) at an interval of 6days for a period of 60 days. AISI 1019 steel were immersed in seawater solution in the absence and presence of varying inhibitor concentrations of potassium chromate (PC), Sodium Nitrite (SN), Methyl Orange (MO), Methyl Red (MR), Terminalia Catappa Leaves (TCL) Extract, Carica papaya Leaves (CPL) Extract. The results showed that there is an increase in inhibition efficiency with increase in inhibitor concentration and decrease in inhibition efficiency with increase in immersion time. The inorganic inhibitor (potassium chromate), inorganic inhibitor (Sodium Nitrite), the organic Inhibitor (Methyl Orange), the organic inhibitor (Methyl Red), the green inhibitor (Terminalia Catappa Leaves) and green inhibitor (Carica Papaya Leaves) produced their best inhibition efficiency of 71.94%, 634%, 68.94%, 68.32%, 62.7%, 59.79% respectively at a concentration of 10g/L. From the result obtained, the potassium chromate inhibitor has better inhibitory property than other inhibitors, which revealed that it is best suited for inhibition of corrosion of mild steel in seawater environment.

Corrosion Inhibition of Mild-Steel in 0.5 M HCl using some prepared 1,2,3-Triazoles Derivatives

The Weight loss was employed to investigate the impact of triazole on mild-steel dissolution in 0.5 M HCl solution. The inhibitor’s inhibition efficiency was seen to increase with concentration yielding (81.61%,82.61%,88.29%,91.64%,94.32%) of (T9, T8, T6, T4, T1) at concentration 1×10-4 M HCl, at a temperature of 25°C for 240 min. At a temperature range from 25–45°C, we studied the temperature impact on the corrosion behavior, wherein the results demonstrated decrease in inhibition efficiency with rising in temperature to achieve (61.7%, 52.26%, 63.1%, 72.11%, 75.77 %) of (T9, T8, T6, T4 and T1) at a concentration of 1×10-4 M, at a temperature 45°C for 240 min. A study was also performed regarding the impact of temperature on the corrosion rate in the presence and absence of triazole. The activation energy and Kinetic parameters were calculated and discussed. Polarization curves revealed that the studied inhibitors represent a mixed – type inhibitors. Adsorption of inhibitors was found to obey Langmuir isotherm and was isotherm physisorption type.

Study on the performance of a scale inhibitor during horizontal-tube falling film evaporation of seawater

Fouling on heat transfer surfaces is a severe problem and a complex phenomenon in multiple-effect distillation plants with horizontal tube falling film evaporators. In general, the scale on heat transfer surfaces is effectively prevented by adding scale inhibitors in large LT-MED seawater desalination plants. This paper presents an experimental study on the performance of a scale inhibitor with different seawater spray temperatures and salinities during falling film evaporation outside the horizontal tubes. The scale inhibitor is developed by the Institute of Water Treatment of Nanjing Tech University. Experiments are performed under the seawater temperature of 70°C, 80°C and 90°C and the salinity of 30g/kg, 60g/kg and 80g/kg. The dosage of the scale inhibitor is 6mg/L. The titanium tubes are used inside the evaporator and Dalian local seawater is selected as the working agent. The scale growing curves under different conditions are obtained through weighting the amount of the scale formed at different periods. The seawater temperature and salinity have a certain influence on the performance of the scale inhibitor during the horizontal-tube falling film evaporation. As the seawater spray temperature rises, the scale inhibition efficiency decreases. With the increase of salinity, the scale inhibition efficiency decreases.

Experimental and Computational Chemistry Studies on the Inhibition Efficiency of Phthalic Acid (PHA) for the Corrosion of Aluminum in Hydrochloric and Tetraoxosulphate (VI) Acids

In this work, phthalic acid is investigated for its corrosion inhibition properties (for aluminum in solutions of HCl and H2SO4) through experimental and computational chemistry methods. The experimental approach was achieved by using gravimetric (weight loss), linear and potentiodynamic polarization techniques as well as two spectroscopic techniques (Fourier transformed infra red and scanning electron microscopy). The theoretical approach incorporated the computation of semi empirical parameters and Fukui functions. Data obtained from weight loss were in strong agreement with those obtained from polarization methods. They generally pointed to the conclusion that phthalic acid inhibited the corrosion of aluminum better in solution of HCl than in solution of H2SO4. The inhibition efficiency of the inhibitor increases with increase in concentration but with increasing period of contact and temperature, the inhibition efficiency notably decreased. Confirmation of a physical adsorption mechanism was established by observed low values of activation energy and free energy of adsorption as well as the trend of decrease in inhibition efficiency with temperature. Frumkin and El awardy et al. adsorption isotherms best fitted the adsorption characteristics of phthalic acid on aluminium (in both HCl and H2SO4 media). The isotherms revealed that the inhibitor occupies more than one adsorption site and exhibited attractive behavior. Calculated quantum chemical parameters were within the range reported for good corrosion inhibitors while Fukui function, Huckel charge, HOMO–LUMO graphs and FTIR analyses indicated that phthalic acid is adsorbed on aluminum surface via the carboxylic oxygen atom.

Ficus racemosaas corrosion inhibitor for mild steel in acid medium

Corrosion inhibitors significantly retard the rate of attack of a corrosive medium on a metal or an alloy when they are added in small concentrations. Their effect on human health and the environment is a very important criterion to be considered when dealing with corrosion inhibitors. Plants are non-toxic, environment-friendly and rich reserves of naturally occurring organic compounds which can aid the corrosion inhibition process. The inhibition effect of Ficus racemosa (FR) leaf extract on the corrosion of mild steel in 0·5 M sulfuric acid solution was investigated by potentiodynamic polarisation and electrochemical impedance spectroscopy. The inhibition efficiency increases with an increase in the concentration of the FR leaf extract, attaining the maximum value at the highest inhibitor concentration of 2500 parts per million. The effect of temperature on the corrosion behaviour of mild steel in 0·5 M sulfuric acid with and without addition of leaf extract was studied in the temperature range of 298–328 K. A decrease in inhibition efficiency was observed with the rise in temperature. Potentiodynamic polarisation data revealed a mixed mode of inhibition. The adsorption process was found to be consistent with Langmuir adsorption isotherm.