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The corrosion inhibition effects of rapeseed meal reflux extract (RMRE) and rapeseed meal ultrasonic extract (RMUE) on CRS in 1.0 M CH 3 COOH media were fully compared and studied using weight loss method, electrochemical techniques, surface analysis, and theoretical calculations. The results showed that both extracts had good corrosion inhibition and both are mixed corrosion inhibitors with cathodic inhibition, with RMRE (86.3 %) having a slightly higher inhibition effect than RMUR (85.3 %). The results of SEM, AFM, and CLSM micro-morphology analyses and contact angle demonstrated that RME effectively reduced the erosion of CH 3 COOH on the steel surface, the degree of roughness is diminished, while the hydrophobicity is augmented. Analysis of the active ingredients showed that guanine, adenine, and linoleic acid are the main effective components in the extract. The preservative effect of RME was primarily attributed to the synergistic effect of multiple components. Theoretical calculations have demonstrated that heterocycles and carboxyl groups present in the active ingredient can act as both electron acceptors and donors, thereby enhancing their interaction with the steel surface. [Display omitted] • Rapeseed meal reflux extract (RMRE) exhibits better inhibition than rapeseed meal ultrasonic extract (RMUE). • The adsorption behavior of both RMRE and RMUE on steel surface obeys Langmuir isotherm. • RERM and REUM are mixed-type inhibitors with "geometric coverage effect". • SEM, AFM, XPS and contact angle confirm the adsorption of RMRE and RMUE on CRS surface. • The active components of RMRE and RMUE are mainly guanine, adenine and linoleic acid. [ABSTRACT FROM AUTHOR]

Plant-based inhibitors have been receiving more and more attentions due to their affordability, widespread availability, and non-toxic nature. Herein, the rapeseed meal extract (RME) is firstly studied as the corrosion inhibitor for steel in sulfuric acid solution. Two RMEs of rapeseed meal reflux extract (RMRE) and rapeseed meal ultrasonic extract (RMUE) were prepared using 60% C 2 H 5 OH as the solvent. The comparison of the inhibition performance of these two extracts on the corrosion of cold rolled steel (CRS) in 0.50 M H 2 SO 4 media was systematically investigated through weight loss measurements, electrochemical tests, and surface morphology observations. The results indicate that both RMRE and RMUE are efficient inhibitors with the maximum inhibition efficiencies of 88.6% and 84.8%, respectively. RMRE exhibits slightly superior performance than RMUE. The adsorption of either RMRE or RMUE on CRS surface fully follows Langmuir-isotherm model. RMRE and RMUE act as mixed-type inhibitors, while prominently retards the cathodic reaction. In the presence of RMRE or RMUE, there is a notable increase in charge transfer resistance on the CRS electrode/solution interface, accompanied by a decrease in double-layer capacitance. FTIR and high liquid chromatography-mass spectrometry (HPLC-MS) suggests that there are several organic molecules containing abundant hydroxyl groups, benzene rings, and N, O heteroatoms in RMRE and RMUE, which can be efficiently absorb on steel surface from X-ray photoelectron spectroscopy (XPS) analysis. Morphological graphs of scanning electron microscope (SEM) and atomic force microscope (AFM) further support the efficient inhibitory action. Both flavonoids and purine compounds are active ingredients those mainly contribute on inhibitive ability of RME, but their inhibition is lower than that of RMRE and RMUE. [Display omitted] • Rapeseed meal reflux extract (RMRE) exhibits slightly superior performance than rapeseed meal ultrasonic extract (RMUE). • The adsorption of RMHE and RMUE on CRS surface fully obeys Langmuir isotherm. • RMRE and RMUE act as mixed-type inhibitors, while prominently retards the cathodic reaction. • The adsorption and inhibition of RMHE and RMUE are confirmed by SEM, AFM and XPS. • Flavonoids and purine compounds are active ingredients, but their inhibition is lower than that of RMRE and RMUE. [ABSTRACT FROM AUTHOR]

• There is a synergism between rubber seed extract (RSE) and KI on cold rolled steel (CRS) in H 2 SO 4 solution. • The addition of KI promotes the adsorption of RSE on CRS surface. • The synergistic inhibited CRS surface appears little corrosion from SEM and AFM. • XPS confirms the synergistic mixture of RSE/KI can efficiently adsorb on CRS surface. • The active components of RSE are gallic acid, caffeic acid, ferulic acid, oleic acid, linoleic acid and linolenic acid. Plant-based inhibitor has emerged an important topic owing to the combing merits of eco-friendly, low cost, rich natural resources as well as easy preparation. Rubber seed is the agricultural waste, and is mainly composed of oil and fatty acids those contain many polar oxygen atoms, and so it can be extracted to prepare the potential corrosion inhibitor. Rubber seed extract (RSE) is prepared using reflux extraction method with the extracting solvent of ethanol aqueous solution. The synergistic inhibition effect of RSE and potassium iodide (KI) on the corrosion of cold rolled steel (CRS) in 0.50 M H 2 SO 4 solution is firstly studied by weight loss, potentiodynamic polarization (PDP) curves and electrochemical impedance spectroscopy (EIS) methods. CRS surface was thoroughly characterized using metallographic microscope, scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. FTIR, UV–vis and liquid chromatography mass spectrometry (LC-MS) compositional analysis of RSE were used to analyze the efficient components in RSE. The results indicate that individual RSE or KI cannot function as a successful inhibitor to prevent CRS corrosion, but the mixture of RSE/KI performs better at inhibiting, with a maximal inhibition efficacy of up to 96.4% of 200 mg L−1 RSE/100 mg L−1 KI. The synergistic coefficient of the mixture is larger than 1, indicating that a true synergism. RSE/KI can drastically retard both cathodic and anodic processes, and interfacial capacitance falls as the charge transfer resistance of CRS/solution rises. It exhibits remarkable inhibition properties when the capacitor arc grows. There is only a small corrosion response in the inhibited media, as evidenced by the variations in electrical conductivity and ultraviolet spectrum before and after immersion. The hydrophilicity and surface roughness of CRS surface is dropped as a result of the introduction of RSE/KI. A series of metallurgical microscopy, AFM, SEM or contact angle tests indicate a synergistic inhibition effect is more pronounced for RSE/KI. XPS results clearly demonstrate that elements including Fe, S, N, and I are bonded to the surface of CRS. The primary ingredients of oleic acid, polyphenols, phenylpropanoids can also produce a strong synergism with KI. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ce(SO 4) 2 is an efficient inhibitor in H 3 C 6 H 5 O 7 , but other rare earth salts are poor. • Ce(SO 4) 2 is a mixed inhibitor through geometric blocking effect. • EIS has two time constants, and the charge transfer resistance is increased with Ce(SO 4) 2. • SEM, AFM and CLSM images confirm the inhibited steel surface appears little corrosion. • Inhibitive mechanism is attributed to adsorption of the complexes of Ce4+-citric anion ions. The inhibition effect of rare earth salt of Ce(SO 4) 2 on the corrosion of cold rolled steel (CRS) in 0.50 M citric acid (H 3 C 6 H 5 O 7) solution was studied by weight loss, electrochemical technique and surface analysis methods for the first time. The results reveal that Ce(SO 4) 2 behaves as an efficient inhibitor, and the maximum inhibition efficiency reaches a pleasant value of 97.2% at 20 °C with a little concentration of 0.25 mM. The adsorption of Ce(SO 4) 2 on CRS surface completely obeys Langmuir adsorption isotherm at 20 - 50°C. Ce(SO 4) 2 is arranged as a mixed-type inhibitor while mainly retards the cathodic reaction. Electrochemical impedance spectroscopy (EIS) has two time constants. Nyquist diagram contains a depressed capacitive loop at high frequencies followed by an inductive loop at low frequencies. The inhibition of CRS surface by Ce(SO 4) 2 is evidenced through scanning electron microscope (SEM), atomic force microscope (AFM) and confocal laser scanning microscope (CLSM). The inhibitive mechanism can be mainly attributed to the complexes of cerium (IV) ion with citric anions. [Display omitted] [ABSTRACT FROM AUTHOR]

• Mixing WGHE and SLS produces synergistic inhibition effect for steel in H 3 PO 4. • All parameters of K, E a , A , ∆ H a and ∆ S a obey the order: WGHE/SLS > WGHE > SLS. • WGHE/SLS mixture acts as a mixed-type inhibitor. • The contact angle of inhibited surface by WGHE/SLS mixture is obtuse angle. • NQ+SLS2− or PC+SLS2− exhibits stronger donating electrons than individual NQ or PC. The synergistic inhibition effect of walnut green husk extract (WGHE) and sodium lignosulfonate (SLS) on the corrosion of cold rolled steel (CRS) in 3.0 M H 3 PO 4 solution was firstly studied by weight loss, electrochemical technique, surface analysis, quantum chemical calculation and molecular dynamics (MD) simulation. Results show that WGHE acts as a moderate inhibitor with a maximum inhibition efficiency of 73.4%, while SLS is poor inhibitor with the maximum inhibition below 40%. Mixing WGHE with SLS produces strong synergistic inhibition effect, and can significantly improve the inhibitive performance with a pleasant maximum inhibition efficiency of 97.2%. The synergism parameter is high than unity, and increases with the inhibitor concentration, but decreases with an increase of temperature. The adsorption of WGHE, SLS or WGHE/SLS obeys Langmuir adsorption isotherm. Individual WGHE or SLS mainly retards cathodic reaction, while WGHE/SLS mixture drastically inhibits both anodic and cathodic reactions simultaneously. The charge transfer resistance is drastically increased for the WGHE/SLS mixture, but the double electric capacitance decreases to more extent. The inhibited CRS surface by WGHE/SLS clearly appears little corrosion from SEM graph, and is of hydrophobic nature with an obtuse contact angle. Two components of naphthoquinone and 2-phenylchromone in WGHE exhibit synergistic inhibition with SLS. Quantum chemical calculations are well accordance with the expected inhibition order of WGHE/SLS > WGHE > SLS. The WGHE/SLS hybrid co-adsorb on Fe (001) and Fe (110) surfaces in the nearly flat manner, and the adsorption energy is more negative comparing with individual WGHE or SLS. [ABSTRACT FROM AUTHOR]

Abstract The inhibition effect of triazolyl blue tetrazolium bromide (TBTB) on cold rolled steel (CRS) in three chlorinated acetic acids of monochloroacetic acid (ClCH 2 COOH), dichloroacetic acid (Cl 2 CHCOOH) and trichloroacetic acid (Cl 3 CCOOH) was studied by weight loss, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) methods. Meanwhile, the adsorption mechanism of TBT+ (organic part of TBTB) was theoretically investigated by quantum chemical calculation and molecular dynamics (MD) simulations. The results show that TBTB acts as a good inhibitor, and inhibition efficiency in three chlorinated acetic acids follows the order: ClCH 2 COOH < Cl 2 CHCOOH < Cl 3 CCOOH. The maximum inhibition efficiency of 1.0 mM TBTB from weight loss method is 85.8% in ClCH 2 COOH; 91.7% in Cl 2 CHCOOH; and 95.5% in Cl 3 CCOOH. The adsorption of TBTB on CRS surface obeys Langmuir isotherm, and the adsorption free energy (Δ G 0) is about −34 kJ mol−1. In each chlorinated acetic acid solution, TBTB behaves as a mixed inhibitor, and the presence of TBTB shifts the both anodic and cathodic curves to lower current densities. With the addition of TBTB, the corrosion potential almost does not alter in ClCH 2 COOH, while becomes more positive in Cl 2 CHCOOH, and moves negative position in Cl 3 CCOOH. EIS exhibits one large depressed capacitive loop at high frequencies followed by a small inductive section at low frequencies. In the presence of TBTB, the charge transfer resistance increases, while both constant phase element and double layer capacitance decreases. SEM micrographs reveal that the corrosion of CRS can be efficiently retarded by TBTB. TBT+ can be further protonated by H+ in acid solution to form TBTH2+. Both TBTH2+ and TBT+ could easily physical adsorb on steel surface owing to high dipole moment values, and TBTH2+ exhibits stronger physisorption than TBT+. The electron densities of both HOMO and LUMO are localized principally on tetrazole and thiazole rings, which are chemical adsorption sites. TBTH2+ strengthens accepting electrons while weakens donating electrons as compared with TBT+. Both TBT+ and TBTH2+ adsorb onto Fe (001) surface with nearly flat orientation mode, and the adsorption energy of TBT+ is a little higher than that of TBTH2+. Graphical abstract Unlabelled Image Highlights • TBTB acts an efficient mixed-type inhibitor for steel corrosion in chlorinated acetic acids. • The adsorption of TBTB obeys Langmuir isotherm, and is the mixed adsorption. • Inhibition efficiency follows the order: ClCH 2 COOH < Cl 2 CHCOOH < Cl 3 CCOOH. • For both TBT+ and TBTH2+, the active adsorption sites are tetrazole ring and thiazole ring. • The adsorptive ability of TBT+ is a little stronger than TBTH2+. [ABSTRACT FROM AUTHOR]

The synergistic inhibition effect of 5-aminotetrazole (AT) and 4,6-dihydroxypyrimidine (DHP) on the corrosion of cold rolled steel (CRS) in H 3 PO 4 solution was studied by weight loss, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), quantum chemical calculation and molecular dynamics (MD) methods. The results show that AT exhibits a moderate inhibitive effect, and DHP has a poor effect. However, incorporation AT with DHP significantly improves the inhibitive performance, and yields synergism. The adsorption of AT in the absence and presence of DHP obeys Langmuir adsorption isotherm. AT/DHP mixture acts as a mixed-type inhibitor. The combined AT and DHP molecules co-adsorb on the Fe (001) surface in the nearly flat manner, and the adsorption energy is larger than individual AT or DHP. [ABSTRACT FROM AUTHOR]

Abstract: The inhibition effect of the bamboo of Dendrocalmus sinicus Chia et J.L. Sun leaf extract (DSCLE) on the corrosion of cold rolled steel (CRS) in 1.0–5.0M HCl, 0.5–5.0M H2SO4 solutions was studied by weight loss, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and atomic force microscope (AFM) methods. The results show that DSCLE is a good inhibitor in 1.0M HCl and 0.5M H2SO4, and inhibition efficiency follows the order: HCl>H2SO4. The adsorption of DSCLE on CRS surface obeys Langmuir adsorption isotherm, and acts as a mixed-type inhibitor in both acids. [Copyright &y& Elsevier]

Abstract: The inhibition effect of allyl thiourea (ATU) on the corrosion of cold rolled steel (CRS) in 1.0M H3PO4 solution at 20–50°C was studied by weight loss, potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) methods. The results show that ATU is a good inhibitor, and the maximum inhibition efficiency of 0.5mM inhibitor is higher than 95% at all studied temperatures. The adsorption of ATU obeys Langmuir adsorption isotherm. Polarisation curves show that ATU behaves as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop. The inhibition action is also evidenced by SEM. [Copyright &y& Elsevier]

Abstract: The inhibition effect of alizarin violet 3B (AV3B) on the corrosion of cold rolled steel (CRS) in 1.0M HCl and 0.5M H2SO4 solutions was investigated for the first time by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that AV3B is a good inhibitor, and exhibits more efficient in 1.0M HCl than 0.5M H2SO4. The adsorption of AV3B on CRS surface obeys Langmuir adsorption isotherm in both acids. Polarization curves reveal that AV3B acts as a mixed-type inhibitor. [Copyright &y& Elsevier]

Abstract: The inhibition effect of three pyrazine derivatives of 2-methylpyrazine (MP), 2-aminopyrazine (AP) and 2-amino-5-bromopyrazine (ABP) on the corrosion of cold rolled steel (CRS) in 1.0M H2SO4 solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that all pyrazine compounds are good inhibitors, and inhibition efficiency follows the order: ABP>AP>MP. The adsorption of each inhibitor on CRS surface obeys Langmuir adsorption isotherm. For all these pyrazine derivatives, they act as mixed-type inhibitors. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory. [Copyright &y& Elsevier]

Abstract: The inhibition effect of nitrotetrazolium blue chloride (NTBC) on the corrosion of cold rolled steel (CRS) in 0.5M H2SO4 was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The results show that NTBC is a good inhibitor, and the adsorption of NTBC on CRS surface obeys Langmuir adsorption isotherm. Polarization curves show that NTBC acts as a mixed-type inhibitor. EIS spectra consist of large capacitive loop at high frequencies followed by a small inductive one at low frequency values, and charge transfer resistance increases with the inhibitor concentration. [Copyright &y& Elsevier]

Abstract: The synergistic inhibition effect of rare earth cerium(IV) ion (Ce4+) and sodium oleate (SO) on the corrosion of cold rolled steel (CRS) in 3.0M phosphoric acid (H3PO4) has been investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) methods. The results reveal that SO has a moderate inhibitive effect and its adsorption obeys Temkin adsorption isotherm. Ce4+ has a poor effect. However, incorporation of Ce4+ with SO improves the inhibition performance significantly, and exhibits synergistic inhibition effect. SO acts as a cathodic inhibitor, while SO/Ce4+ mixture acts as a mixed-type inhibitor. [Copyright &y& Elsevier]

Abstract: The inhibition effect of 6-benzylaminopurine (BAP) on the corrosion of cold rolled steel (CRS) in 1.0–7.0M H2SO4 at 25–50°C was studied by weight loss and potentiodynamic polarization methods. Fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM) were used to characterize the CRS surface. The results showed that BAP was a good inhibitor in 1.0M H2SO4, and the adsorption of BAP obeyed the Temkin adsorption isotherm. Polarization curves showed that BAP acted as a mixed-type inhibitor in sulfuric acid. Depending on the results, the inhibitive mechanism was proposed. [Copyright &y& Elsevier]

• CDEA is an efficient inhibitor for steel corrosion in HCl and H 2 SO 4. • The adsorption of CDEA is endothermic with an increase of entropy. • CDEA acts as a mixed-type inhibitor through "geometric blocking effect". • The inhibited CRS is of hydrophobic with little corrosion and more smoother. • The active site of CDEA is —CON(CH 2 CH 2 OH) 2 , and its CMC is 0.10 mM. Nonionic surfactant has the combined merits of easy production, low toxicity and high surface activity, which can be deemed as the potential inhibitor with good prospect. The nonionic surfactant of coconut diethanolamide (CDEA) has no cloud point comparing with other nonionic surfactants, and the acylamide group of O=C-N in its hydrophilic head can make the good hydrolysis resistance of CDEA. The inhibition effect of CDEA was studied as a novel corrosion inhibitor for cold rolled steel (CRS) in both HCl and H 2 SO 4 solutions for the first time by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The micro-morphologies and chemical compositions of CRS surfaces were fully characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscope (AFM), confocal laser scanning microscope (CLSM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The critical micelle concentration (CMC) values of CDEA in HCl and H 2 SO 4 media were determined by surface tension measurements. Moreover, quantum chemical calculations and molecular dynamic (MD) simulations were used to theoretically study the adsorption sites and modes of CDEA. CDEA acts as an efficient inhibitor, and the maximum inhibition efficiency of 50 mg L−1 CDEA is above 95% in 1.0 M HCl, and 92% 0.5 M H 2 SO 4 from weight loss method. The adsorption of CDEA on CRS surface completely obeys Langmuir isotherm, and the standard adsorption Gibbs free energy is around -40 kJ mol−1. CDEA can be arranged as a mixed-type inhibitor in both acids, while exhibits more anodic inhibition in HCl solution. The presence of CDEA significantly increases the charge transfer resistance, while decreases the double layer capacitance. Inhibition efficiency follows the order: 1.0 M HCl > 0.5 M H 2 SO 4. A series of micro-morphologies of CRS surfaces by SEM, AFM and CLSM confirm efficient inhibition of CDEA for steel in strong acids. EDX and XPS provides the distinct proof of adsorption of inhibitor molecules. The inhibited CRS surface is turned to be hydrophobic with an obtuse contact angle. The adsorption reaches saturated state at CMC of 0.10 mM. The hydrophilic groups of —OH and —CON— are the active adsorption sites of CDEA, while the hydrophobic chain of —C 11 H 23 extends to the aqueous solution phase. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The synergism between rare earth cerium(IV) ion and vanillin on the corrosion of cold rolled steel (CRS) in 1.0M HCl solution was first investigated by weight loss, potentiodynamic polarization, ultraviolet and visible spectrophotometer (UV–vis), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). The results revealed that vanillin had a moderate inhibitive effect, and the adsorption of vanillin obeyed the Temkin adsorption isotherm. For rare earth Ce4+, it had a negligible effect. However, incorporation of Ce4+ with vanillin significantly improved the inhibition performance, and produced strong synergistic inhibition effect. Depending on the results, the synergism mechanism was proposed. [Copyright &y& Elsevier]

Abstract: The synergistic inhibition effect of rare earth cerium(IV) ion and anionic surfactant of sodium oleate (C17H33–COONa, SO) on the corrosion of cold rolled steel (CRS) in H2SO4 solution was first investigated by weight loss and potentiodynamic polarization methods. The results revealed that SO had a moderate inhibitive effect, and the adsorption of SO obeyed the Freundlich adsorption isotherm. For the cerium(IV) ion, it had a negligible effect. However, incorporation of Ce4+ with SO significantly improved the inhibition performance, and produced strong synergistic inhibition effect. Depending on the results, the synergism mechanism was proposed. [Copyright &y& Elsevier]

[Display omitted] • The biodegradable surfactant-dodecyl dimethyl betaine (BS-12) was used as metal inhibitor. • Traces of BS-12 (10 mg·L−1) showed high inhibition efficiency (95.3 %) to cold-roll steel (CRS). • The MD simulations showed that the BS-12 adsorbed on the CRS surface horizontally. • The density of state proved that the electron transfer within BS-12 and CRS. • Adding BS-12 had no side effect on the performance of the nanofiltration membrane. The membrane process is an effective way to realize resource reutilization. Most membrane devices are made of cold-roll steel (CRS), which is easy to corrode when operating in acid conditions. Herein, the biodegradable surfactant dodecyl dimethyl betaine (BS-12) was used as the inhibitor to protect the CRS in the trichloroacetic acid (TCA) solution. The long-term stability membrane tests showed that adding BS-12 will not harm the membrane performance. The weight loss experiments proved that adding BS-12 with trace amount (10 mg·L−1) endowed the CRS with good inhibition efficiency (95.3 %). The electrochemical tests indicated that the mixed inhibitor- BS-12 works by inhibiting the anode and cathode simultaneously, and the polarization resistance increased to 21 times. The SEM, AFM, and CLSM tests proved that adding BS-12 enabled the CRS surface to remain stable. The FTIR and XPS tests proved that BS-12 adsorbed on the CRS surface via physical and chemical adsorption. The theoretical calculations proved the horizontal adsorption of BS-12 on the CRS surface and the existence of the electron transfer within the BS-12 and CRS. The BS-12 showed great potential in the CRS inhibition of the membrane separation and purification processing. [ABSTRACT FROM AUTHOR]

[Display omitted] • N1 of DDAC and N13 of BDDACP are the most vulnerable to electrophilic attack. • BDDACP can form a robust protective film in a parallel direction on Fe (1 1 0) plane. • BDDACP functions as a mixed inhibitor that primarily impedes the active site of CRS surface. • The chemical bonds between BDDACP molecules and Fe atoms are detected from the inhibited CRS surface. • A novel Gemini surfactant of BDDACP is an efficient inhibitor for steel in HCl media with good application prospect. Gemini surfactants have become the research focus of novel excellent inhibitors because of their special structure (two amphiphilic moieties covalently connected at head group by a spacer) and excellent surface properties. It is proved by theoretical calculations that 1, 3-bis (dodecyl dimethyl ammonium chloride) propane (BDDACP) molecules can perform electron transfer with Fe (1 1 0). And it has a small fraction free volume, thus greatly reducing the diffusion and migration degree of corrosive particles. The potentiodynamic polarization curve showed that coefficients of cathodic and anodic reaction less than 1 and polarization resistance increased to 1602.9 Ω cm−2 after added BDDACP, confirming that BDDACP significantly inhibited the corrosion reaction by occupying the active site. The electrochemical impedance spectrum of imperfect semi-circle shows that the system resistance increases and double layer capacitance after added BDDACP. Weight loss tests also confirmed that BDDACP forms protective film by occupying the active sites on steel surface, and the maximum inhibition efficiency is 92 %. Comparison of the microscopic morphology showed that steel surface roughness was significantly reduced after added BDDACP. The results of time-of-flight secondary ion mass spectrometry show that steel surface contains some elements from BDDACP, which confirms the adsorption of BDDACP on steel surface. [ABSTRACT FROM AUTHOR]

• The corrosion inhibition properties of thiourea derivatives on CRS were studied. • Thiourea derivatives have significant corrosion inhibition effects. • The corrosion inhibition efficiency of p-TTU was as high as 97.36%. • Theoretical dates provide in-depth understanding of the experimental results. • The introduction of group modifications in TU improves its inhibition properties. The prediction of the corrosion inhibition properties of organic compounds from experimental and computational results is a highly interesting field. Correct understanding of substituents or electronic effects can significantly contribute to the design of efficient inhibitors. In this research article, the corrosion inhibitory performance of thiourea (TU), 1,3-dimethylthiourea (DMTU), N-ethylthiourea (ETU), and 1-p-tolylthiourea (p-TTU) in 1.0 M citric acid (H 3 C 6 H 5 O 7) solution for cold rolled steel (CRS) was fully investigated by experimental measurements and theoretical calculations. The results show that the inhibition performance of p-TTU exhibits the best inhibition property among these four thiourea derivatives with a maximum inhibition efficiency of 97.36%. The inhibition ability follows the order of p-TTU > DMTU > ETU > TU. Potentiodynamic polarization curves indicate that all these thiourea derivatives are mixed-type inhibitors, where TU, ETU and DMTU mainly inhibit the cathodic reaction, but p-TTU effectively retards both cathodic and anodic reactions. Nyquist mainly appears a depressed capacitive loop, and the charge transfer resistance increases significantly with the addition of thiourea derivatives. The adsorption of four thiourea derivatives on CRS surface conforms to Langmuir adsorption isotherm. The micrographs from SEM and metallurgical microscopy further support the protection effectiveness of thiourea derivatives on the steel surfaces. Quantum chemical calculations and molecular dynamics simulations can well elucidate the relationship between molecular structure and inhibition efficiency for the studied thiourea derivatives. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Eupatorium Adenophora Spreng leaves extract (EASLE) is an efficient inhibitor for steel in ClCH 2 COOH. • The inhibited steel surface is of hydrophobicity with little corrosion and low surface roughness from SEM, AFM and CLSM micrographs. • EDS, XPS and TOF-SIMS confirms that EASLE can efficiently adsorb on steel surface. • EASLE behaves as a hybrid inhibitor through "geometric blocking effect". • O -cresol, erucamide, vanilin, 3-phenoxybenzoic acid, p -coumaric acid and adenine are active ingredients in EASLE. Traditional inhibitors are restricted due to their high price and high toxicity. Plant extracts as green inhibitors can be used as an alternative to traditional inhibitors due to their merits of low price, eco-friendly, and rich resources. The inhibitive action and mechanism of Eupatorium Adenophora Spreng leaves extract (EASLE) on the corrosion of cold rolled steel (CRS) in chloroacetic acid (ClCH 2 COOH) medium was investigated for the first time. The maximum inhibition efficiency of EASLE is 94.9% even at higher temperature of 50 °C. The surface micro-topography of inhibited CRS is relatively flat from SEM, AFM and CLSM images, and C/N/O elements contained in EASLE can form coordinated bonds with Fe atoms, as observed through XPS and TOF-SIMS. The adsorption of EASLE mainly occurs through chemisorption and is consistent with Langmuir isotherm. EASLE acts as a hybrid inhibitor, and its inhibitive mechanism is consistent with "geometric blocking effect". The charge-transfer resistance turns to be higher after adding EASLE, and there is a single time constant. All the main inhibiting components of o -cresol, erucamide, vanillin, 3-phenoxybenzoic acid, p -coumaric acid, and adenine in EASLE exhibit the inhibition efficiency of approximately 80% in ClCH 2 COOH. Theoretical calculations suggest that benzene rings, heterocycles, and carboxyl groups are derived from these active components can be used as both electron acceptors and provider. The hydrophilic group can actively adsorb to CRS surface through heteroatoms of erucamide, while the hydrophobic group with a long carbon chain extends to the aqueous phase to form a protective barrier. EASLE can be an excellent substitute for traditional inhibitors, which are of both economic and environmental values. [ABSTRACT FROM AUTHOR]

The synergistic inhibition effect of Mikania micrantha extract (MME) with KI mixture on the corrosion of cold rolled steel (CRS) in methanesulfonic acid (MSA) was conducted by weight loss, electrochemical techniques and surface characterizations. The experimental results indicate that either MME or KI performs moderate inhibition with a maximum inhibition efficiency below 74%. However, MME / KI mixture exhibits an efficient performance with a maximum inhibition efficiency of 91%. There is a synergism between MME and KI with a corresponding synergism parameter higher than 1. The alien invasive weed can be developed as a novel inhibitor against metallic corrosion. [Display omitted] • Incorporation MME with KI produces synergism for steel in methanesulfonic acid. • The addition of KI promotes the adsorption of MME on steel surface. • The synergistic inhibited steel surface appears little corrosion from SEM, AFM and CLSM. • XPS confirms the synergistic mixtures of MME/KI can efficiently adsorb on CRS surface. • The synergistic inhibited CRS surface provides a stronger hydrophobicity. [ABSTRACT FROM AUTHOR]

Mikania micrantha extract (MME) was prepared by reflux extraction from the exotic invasive weed of Mikania micrantha using ethanol water solution as the solvent. The synergistic inhibition effect and mechanism of MME and potassium iodide (KI) on the corrosion of cold rolled steel (CRS) in 4.0 M H 3 PO 4 solution was investigated by gravimetric, electrochemical and surface analysis techniques for the first time. The results show that either MME or KI has moderate inhibitive action, and the maximum inhibition efficiency is below 65 % at 20 ℃. However, incorporation MME with KI can produce a synergism (s > 1), and obtain a pleasant inhibition of 92.9%. The adsorption of MME on CRS surface obeys Freundlich isotherm, while KI and MME/KI complex follow Langmuir isotherm. They are all mixed-type inhibitors, and MME/KI mixture significantly retards the electrochemical corrosion comparing with individual MME or KI. The process of electrochemical corrosion is controlled by charge transfer, and the charge transfer resistance follows the order of MME/KI > KI > MME. SEM and AFM demonstrate that the corrosion of CRS surface is efficiently retarded by the blend of MME and KI. From FTIR and XPS analysis, the formed layer of the synergistic inhibited CRS surface is mainly composed of the organic compounds with polar groups in MME. There is also a synergistic inhibition of the major components (rutin, quercetin, chlorogenic acid and ferulic acid) with KI. MME/KI can be deemed as a novel efficient inhibitor for steel in concentrated phosphoric acid, which develops an original path for the utilization of Mikania micrantha in the field of metallic corrosion and protection. [Display omitted] • Incorporation Mikania micrantha extract with KI produces synergism for steel in 4.0 M H 3 PO 4. • The addition of KI promotes the adsorption of Mikania micrantha extract on steel surface. • Both cathodic and anodic reactions are more efficiently retarded by MME/KI mixture. • The synergistic inhibited steel surface appears little corrosion and low surface roughness. • Flavonoids and phenylpropanoids are effective components those contribute on synergism. [ABSTRACT FROM AUTHOR]