Corrosion Inhibitor Concentration Research Articles

Experimental and theoretical investigation of 1-Hexyl-3-methylimidazolium iodide as a corrosion inhibitor for mild steel in HCl environment

This study employed 1-Hexyl-3-methylimidazolium iodide to mitigate the corrosion of Q235 steel in a hydrochloric acid environment. The evaluation of corrosion inhibition effectiveness was comprehensively characterized by combining electrochemical experiments with surface morphology observation. The experimental results demonstrated the capability of the ionic liquid in establishing a film layer on the surface of Q235 steel, which effectively hindered the charge transfer process. Notably, the corrosion inhibition efficiency attained a value of 92.3% at a concentration of 1 mM corrosion inhibitor. Moreover, the process of the corrosion inhibitor adhering to the steel surface aligns with the Langmuir isotherm, demonstrating physicochemical adsorption behavior. The density functional theory (DFT) and molecular dynamics (MD) simulation were utilized for further exploration of the corrosion inhibition mechanism, and the results indicate the ionic liquid can be adsorbed onto the (110) surface of Fe in parallel through N atoms on the imidazole ring.

INVESTIGATION OF RESISTANCE TO PITTING CORROSION OF STRUCTURAL MATERIALS OF THE BN-350 REACTOR

The article is devoted to the study of the resistance of structural materials of the BN-350 reactor to pitting corrosion in an aqueous medium containing chlorine ions in the presence of organic corrosion inhibitors. The results of accelerated testing of samples of austenitic steels 12Cr18Ni10Ti, 08Cr16Ni11Mo3Ti and Cr13Mo2NbVB (EP-450) ferrite-martensitic steel for pitting corrosion in a 10% aqueous solution of iron three-chloride hexahydrate without an inhibitor and in the presence of various concentrations of corrosion inhibitor are presented. The effect of heat treatment on the pitting resistance of structural steels is studied and the role of carbide precipitates of MC and M23C6 types in pitting defects formation is discussed.

Carbon steel behavior towards Cucumeropsis mannii shell extract as an ecofriendly green corrosion inhibitor in chloride medium

This study advanced on previous studies by investigating the hardness and tensile strength of carbon steel under different loads after determining the corrosion rate at different temperature, immersion time and corrosion inhibitor concentration in a chloride medium using Cucumeropsis mannii shell extract (CMSE) as an eco-friendly green corrosion inhibitor. The inhibition efficiency was evaluated by weight loss, electrochemical impedance spectroscopy and potentiodynamic polarization techniques. Adsorption behavior and material characterization were investigated. The result revealed maximum inhibition efficiency of 92.2% and 91.2% could be attained by EIS and PDP techniques respectively. The corrosion rate decreases as the inhibitor's concentration increases and vice versa for temperature and immersion time. The Young modulus and hardness of carbon steel decreased at higher load under corrosion attack in the absence of CMSE. The green corrosion inhibitor exhibited a mixed-type with a spontaneous physisorption behavior on carbon steel surface. Material characterization revealed presence of active functional groups in the extract with formation of uniform and pitting corrosion on carbon steel surface. In conclusion, Cucumeropsis mannii shell extract behaved excellently as corrosion inhibitor for carbon steel in chloride solution.

Data-driven corrosion inhibition efficiency prediction model incorporating 2D–3D molecular graphs and inhibitor concentration

Following the construction of a dataset of cross-category corrosion inhibitors at different concentrations based on 1241 data from 184 research papers, a performance prediction model incorporating 2D–3D molecular graph representation and corrosion inhibitor concentration information was established. This model was shown to effectively predict the inhibition efficiency (IE) of different categories of corrosion inhibitors for carbon steel in 1 mol/L HCl solution. The model was also able to predict IEs of corrosion inhibitors at different concentrations. The results demonstrated that 3D features of corrosion inhibitors, especially those of large molecules, had a significant impact on the prediction precision of IEs.

Preparation of Bis-Thiophene Schiff Alkali-Copper Metal Complex for Metal Corrosion Inhibition.

Due to the obvious numerous economic and technical consequences of the corrosion process, its inhibition is one of the most critical aspects of current research. A corrosion inhibitor for the bis-thiophene Schiff base copper-metal complex Cu(II)@Thy-2 was investigated here, which was synthesized via a coordination reaction with a bis-thiophene Schiff base (Thy-2) as a ligand and copper chloride (CuCl2-2H2O) as a ligand metal salt. When the corrosion inhibitor concentration was increased to 100 ppm, the self-corrosion current density Icoor reached a minimum of 2.207 × 10-5 A/cm2, the charge transfer resistance reached a maximum of 932.5 Ω·cm2, and the corrosion inhibition efficiency reached a maximum of 95.2%, with the corrosion inhibition efficiency showing a trend of increasing first and then decreasing with concentration increase. After adding Cu(II)@Thy-2 corrosion inhibitor, a uniformly distributed dense corrosion inhibitor adsorption film formed on the surface of the Q235 metal substrate, significantly improving the corrosion profile compared to both before and after the addition of the corrosion inhibitor. Before and after the addition of corrosion inhibitor, the metal surface's contact angle CA increased from 54.54° to 68.37°, showing that the adsorbed corrosion inhibitor film decreased the metal surface's hydrophilicity and increased its hydrophobicity.

Synthesis of a Hydroxyl-Containing Corrosion Inhibitor and Its Inhibitory Performance on N80 Steel in Hydrochloric Acid Solution

In the process of petroleum exploitation, in order to effectively inhibit the corrosion damage of acid to metal equipment. Mannich base corrosion inhibitors are generally added to inhibit the corrosion damage of acid. In order to enhance the solubility of Mannich base corrosion inhibitor. This paper intends to introduce hydrophilic groups to enhance the solubility of the Mannich base corrosion inhibitor. In this paper, two efficient corrosion inhibitors 3-(2-hydroxyethylamino)-1-phenylpropan-1-one (MY1) and 3-(2-aminoethylamino)-1-phenylpropan-1-one (MY2), were synthesized based on the Mannich reaction, using formaldehyde, acetophenone and ethanolamine/ethylenediamine as reaction raw materials. The corrosion inhibition performance of the inhibitor on N80 steel in 15% (mass fraction) hydrochloric acid solution was studied by means of the static weight loss method, electrochemical test and optical contact angle analysis. It could be seen from the static weight loss method that the corrosion rate in the hydrochloric acid solution before and after adding 0.7% (mass fraction) corrosion inhibitor concentration decreased from 129.39 g·m−2·h−1 to 1.45 g·m−2·h−1 and 2.79 g·m−2·h−1, respectively. The corrosion inhibition rate could reach 98%, indicating that both inhibitors had good corrosion inhibition performance, and the corrosion inhibition effect of MY1 was better than that of MY2. It was found from the electrochemical tests that the two inhibitors were mixed corrosion inhibitors mainly inhibiting the anodic reaction, and both inhibitors belonged to spontaneous adsorption, and their adsorption behaviors followed the Langmuir adsorption isotherm. In addition, the surface of N80 steel was characterized by SEM, EDS elemental mapping and contact angle measurement. The results show that a dense hydrophobic film is formed on the surface of the steel sheet after the addition of a corrosion inhibitor, which prevents corrosion.

Numerical simulation study of corrosion behavior of Ni-P coating under multiple working conditions

The research on marine corrosion protection is very important in modern naval warfare. In this paper, combined with the working environment and usage requirements of underwater equipment, a 3D modeling is carried out based on a certain type of underwater equipment, and the model was divided into regions according to the difference between the base material, and the electrochemical corrosion protection was established through the finite element simulation software COMSOL Multiphysics. The simulation model was used to simulate and analyze the corrosion laws of various parts of the equipment under three different working conditions. According to the simulation results, the corrosion rate of the equipment under the protection of Ni-P chemical coating is much lower than the natural corrosion rate and the corrosion rate in seawater with a 30% concentration of Na2SO3 corrosion inhibitor, and the Ni-P chemical coating has a good anti-corrosion effect. This paper puts forward suggestions for the follow-up improvement and development of the corrosion protection research of this type of underwater equipment and provides a reference for the research on the corrosion behavior of other metals.

Smart lignin-based polyurethane conjugated with corrosion inhibitor as bio-based anticorrosive sublayer coating

Incorporating corrosion inhibitors in the formulation of coatings can yield active coatings which are able to provide a sustained release of the corrosion inhibitor in the case of emergence of microcrack in the structure of the coating. Herein, we developed bio-based polyurethane sublayer coatings with strong anticorrosion performances. First, lignin-corrosion inhibitor (LCI) conjugate was obtained through conjugation of nicotinic acid to lignin through hydrolytically cleavable ester linkage to afford the steady release of low concentrations of corrosion inhibitor in case of the emergence of microcracks. Subsequently, solution polyaddition of LCI with diisocyanates and polypropylene glycol and coating on the stainless steel surface afford the polyurethane coatings. Coating with a thickness of 16 µm increased the E corr from − 481 mV (for bare steel) to + 187 mV and reduced both I corr and corrosion rate more than 6700 times. As an added benefit, after creating artificial cracks on the surface of the coating, the release of corrosion inhibitors gradually increased the impedance value, indicating a thin barrier layer has formed within the cracks. • -Lignin-corrosion inhibitor conjugate was prepared as anticorrosive polyol precursor. • -Anticorrosive polyurethane coatings were fabricated based on lignin precursor. • -Thickness of 16 µm of this coating reduce the corrosion rate over 6700 times. • -The corrosion inhibitor released by the coating inhibits corrosion in microcracks.

Role of SnO2 Nanoparticles for a Self-Forming Barrier Layer on a Mild Steel Surface in Hydrochloric Acid Medium Containing Piper betle Leaf Extract.

The self-formation of a porous organic thin-film via corrosion inhibitor supports wide applications of carbon steel in industry. Unfortunately, serious damages could be concentrated to the pinhole and/or pore locations in the porous organic film, resulting in the localized corrosion even when an optimal concentration of organic corrosion inhibitors is used. In this work, SnO2 nanoparticles are used for producing the more robust barrier layer via the self-migration of nanoparticles, resulting in a higher corrosion resistance, smooth and uniform protective layer, as well as the existence of SnO2 in the protective layer that could directly affect the high inhibition performance. Therefore, the work suggests a new way to make a more robust thin film that could extend the use of organic corrosion inhibitors.

Electrochemical, Isotherm, and Material Strength Studies of Cucumeropsis mannii Shell Extract on A515 Grade 70 Carbon Steel in NaCl Solution

In this study, corrosion inhibition efficiency of Cucumeropsis mannii shell extract (CMSE) was tested on A515 Grade 70 carbon steel in 1.0 M NaCl solution. Potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and weight loss (WL) measurements were used to investigate the inhibition efficiency. Scanning electron microscopy, Fourier transform infrared spectroscopy, atomic adsorption spectroscopy, and energy dispersive spectroscopy were used to characterize the carbon steel and extract. PDP and EIS measurements revealed maximum inhibition efficiency of 91.2% and 92.2%, respectively. Tafel plot confirmed inhibitor to be a mixed type. A monolayer adsorption of CMSE molecules occurred spontaneously by physisorption. Polarization resistance increased with increasing inhibitor concentration. WL measurement revealed decrease in corrosion rate with increasing concentration of corrosion inhibitor. Maximum Young modulus and hardness of 202.4 GPa and 112.3 BHN, respectively, were recorded for the carbon steel at a minimum corrosion rate and load. Pitting and uniform corrosion were formed on the carbon steel in the absence of CMSE. CMSE contains –OH, –OCH3, and –C-NH3 as active functional groups. In conclusion, Cucumeropsis mannii shell extract acted excellently as corrosion inhibitor for A515 Grade 70 carbon steel in 1.0 M NaCl.

Synthesis, Characterisation and Corrosion Inhibition of Mild Steel by Butyltin(IV) 2-Acetylpyridine 4-Methyl-3-Thiosemicarbazone in HCl

Schiff base ligand, 2-acetylpyridine 4-methyl-3-thiosemicarbazone (Me-LH), and its organotin complex (BuSn(Me-LH)Cl2) were synthesized, characterized, and subjected to corrosion inhibition study. The spectra and crystal structure obtained revealed that the ligand is coordinated by pyridyl nitrogen, azomethine nitrogen, and thiolate sulfur to organotin (IV) ion. Corrosion inhibition of the synthesized compounds on mild steels in 1 M HCl solution at different concentrations were tested using weight loss, Electrochemical Impedance Spectroscopy (EIS), potentiodynamic polarization, Scanning Electron Microscopy (SEM) and adsorption analyses. Corrosion inhibition results showed that the complex had a strong corrosion inhibitory effect in comparison to the ligand. The inhibition efficiency of all the techniques improved with an increase in the concentration of corrosion inhibitor. Polarization analysis results showed that the compounds can be categorized as mixed-type inhibitors. Meanwhile, the EIS study indicates that with an increase in the concentration of corrosion inhibitor, the resistance to charge transfer increased. This resulted in the adsorption of inhibitors and the development of a protective layer on the mild steel surface which was further confirmed by SEM analysis. The adsorption isotherm of compounds on a mild steel surface followed the Langmuir isotherm model.
 HIGHLIGHTS
 
 The efficient method to inhibit the corrosion rate of mild steel in an acidic medium is a corrosion inhibitor
 The electrochemical and weight loss analysis proved that the corrosion inhibition efficiency increases when the concentration of inhibitor is increased
 The study proved that the thiosemicarbazone complex showed the potential as corrosion inhibitors at low concentrations
 
 GRAPHICAL ABSTRACT

Fenton Reaction for Enhancing Polishing Rate and Protonated Amine Functional Group Polymer for Inhibiting Corrosion in Ge1Sb4Te5 Film Surface Chemical-Mechanical-Planarization

A Fenton reaction and a corrosion inhibition strategy were designed for enhancing the polishing rate and achieving a corrosion-free Ge1Sb4Te5 film surface during chemical-mechanical planarization (CMP) of three-dimensional (3D) cross-point phase-change random-access memory (PCRAM) cells and 3D cross-point synaptic arrays. The Fenton reaction was conducted with 1,3-propylenediamine tetraacetic acid, ferric ammonium salt (PDTA–Fe) and H2O2. The chemical oxidation degree of GeO2, Sb2O3, and TeO2 evidently increased with the PDTA–Fe concentration in the CMP slurry, such that the polishing rate of the Ge1Sb4Te5 film surface linearly increased with the PDTA–Fe concentration. The addition of a corrosion inhibitor having protonated amine functional groups in the CMP slurry remarkably suppressed the corrosion degree of the Ge1Sb4Te5 film surface after CMP; i.e., the corrosion current of the Ge1Sb4Te5 film surface linearly decreased as the corrosion inhibitor concentration increased. Thus, the proposed Fenton reaction and corrosion inhibitor in the Ge1Sb4Te5 film surface CMP slurry could achieve an almost recess-free Ge1Sb4Te5 film surface of the confined-PCRAM cells, having an aspect ratio of 60-nm-height to 4-nm-diameter after CMP.

Eco-friendly biomass from Ziziphus spina-christi for protection of carbon steel in acidic conditions – Parameter effects and corrosion mechanism studies

The eco-friendly plant extract based corrosion inhibitor, synthesized using Ziziphus spina-christi, was investigated for its corrosion control and surface protection potential for carbon steel under acidic conditions. The influence of process parameters, corrosion inhibitor concentration (160–810 ppm), operating temperature (330.15–315.15 K) and immersion time (4–24 h), on inhibition efficiency was evaluated. Based on mass loss experiments, the maximum inhibition efficiency achieved was found to be 91.35% at 810 ppm inhibitor concentration and 300.15 K. Corrosion rate decreased with increase in inhibitor dose which could be due to enhanced surface coverage. The activation energy associated with this process indicated surface interaction as the main mechanism and positive values of enthalpy change confirmed the endothermic nature. The electrochemical parameters, namely corrosion potential (Ecorr), anodic and cathodic Tafel constants (βa and βc), and corrosion current density (icorr) were calculated, and the inhibitor was found to be mixed type. Through double-layer capacitance, the increase in corrosion resistance was proved. The active functional groups associated with corrosion inhibitor were identified.

Experimental and theoretical studies of chitosan derivatives as green corrosion inhibitor for oil and gas well acid acidizing

Chitosan is a widely distributed recyclable green resource in nature. Because of the particular molecular structure, chitosan derivatives have become an effective way to research environmental friendly corrosion inhibitors for oil and gas well acidizing. In this study, four chitosan derivatives were synthesized and investigated as green corrosion inhibitors for P110 steel in 15% HCl solution in various ways, including weight loss, scanning electron microscopy (SEM), electrochemical measurements (EIS), energy dispersive spectrum (EDS) and molecular dynamic simulations. The experimental results demonstrate that four chitosan inhibitors have an excellent inhibition effect, and there is an obvious negative correlation between the concentration of corrosion inhibitor and the inhibition efficiency. Finally, the erosion effect of the fluid on the corrosion inhibitor layer was studied under different flow velocity conditions and pipeline positions in oil and gas well. The results reveal that the erosion effect of the pipe is proportional to the inlet velocity of the fluid. Chitosan is widely distributed in crustacean, and because of the particular molecular structure, research modified chitosan become an effective way to develop environmental friendly corrosion inhibitors. In this study, chitosan derivatives were synthesized and investigated as green corrosion inhibitors for P110 steel in 15% HCl solution. The erosion effect of the fluid on the corrosion inhibitor layer was studied under different flow velocity conditions and different pipeline positions in oil and gas well. The experimental results demonstrated the chitosan derivatives have an excellent inhibition effect due to adsorbed on the steel surface. Therefore, as a recyclable green resource, chitosan derivatives as corrosion inhibitors have a great prospect in the field of oil and gas development. • Four chitosan derivatives as green corrosion inhibitors were synthesized. • Four inhibitors have an excellent inhibition effect for steel. • The erosion effect of the pipe is proportional to the inlet velocity of the fluid.

Synergistic inhibition effect of Mikania micrantha extract with KI on steel corrosion in H2SO4 solution

Mikania micrantha extract (MME) was prepared by reflux extraction method with 40% C2H5OH water solution. The synergistic inhibition effect of MME and potassium iodide (KI) on cold rolled steel (CRS) in 0.50 M H2SO4 solution was studied by weight loss and electrochemical methods for the first time. The CRS surfaces were fully characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Meanwhile, the main effective compounds in MME were discussed in depth by high performance liquid chromatography (HPLC). The results show that either MME or KI acts as a moderate inhibitor on CRS in 0.50 M H2SO4 solution, and the maximum inhibition efficiency is below 80%. The mixture of MME/KI has a pleasant inhibition performance with the maximum inhibition efficiency of 94.4%. There is an evident synergistic effect between MME and KI, and the corresponding synergism parameter is higher than 1. Regardless of the extra addition of KI, the adsorption of MME obeys the Langmuir adsorption isotherm. The presence of KI enhances the adsorption of MME owing to larger value of adsorption equilibrium constant for MME/KI mixture. MME is a cathodic inhibitor, while MME/KI can be arranged as a mixed-type inhibitor, and the inhibition of both cathodic and anodic reactions is further enhanced by the MME/KI combination. Nyquist diagram mainly exhibits a capacitor loop that is controlled primarily by charge transfer. As the concentration of corrosion inhibitor increases the capacitance arc length gradually increases, especially for MME/KI mixture. The charge transfer resistance increases more than 10 times and shows excellent corrosion inhibition. SEM and AFM clearly confirm that the presence of MME/KI has a significant effect on inhibiting the corrosion of CRS, and the inhibition is expected to follow the order: MME/KI > KI > MME. XPS reveals that the MME/KI mixture can adsorb on steel surface to achieve inhibitive film. Most important, there is also a synergistic inhibition of effective components in MME (chlorogenic acid, ferulic acid) with KI.

Self-Healing Coatings for Corrosion Protection: The Importance of the Transport of Active Agents from the Coating Towards the Defect

In so called smart or intelligent self-healing coatings active agents that are safely stored inside the coating are released upon onset of corrosion. This release is triggered by a suitable trigger signal that should be a safe indicator for the onset of corrosion and its continuation. Different from the current standard where release from pigments occurs via leaching, the safe storage should ensure that there is no uncontrolled release of the active agents when they are not needed for inhibiting corrosion and restoring protection. While there are many studies on different concepts for storage and active release triggered by corrosion, achieving an efficient transport of the released agents to the defective site(s) is a likewise crucial but so far widely neglected issue. Recently it was proposed that the signal spreading from the defect into the coating can be significantly enhanced by the use of layers of conducting polymer, such as polypyrrole, applied as an intermediate layer between the metal substrate and the organic coating. In that case the decrease in potential is the signal that is spread. Here, we will show that by such polypyrrole layers also the transport of active agents can be significantly enhanced. To enable a fundamental in-depth study of the mobility of active agents from the coating towards the defective site, a dedicated experimental model set-up was designed especially for the study of ions transport. The main question to be addressed was whether the main transport will be along the metal│PPy interface or rather through the matrix of the reduced polypyrrole. Zinc was chosen as metallic substrate, owing to its importance in galvanized steel products. The corrosion potential at the defective site was used as a measure for the amount of corrosion inhibitor released into the defect and hence as a measure to reflect the ionic transport and self-healing efficiency of the coating by different corrosion inhibitors. The progress of polypyrrole reduction, in turn, was monitored by use of Scanning Kelvin Probe (SKP) for recording the change of potential as a function of distance from the defect and of time. The concentration of corrosion inhibitor at the defective site was also quantified using ICP-MS (OES) analysis of the solution in the defect at different times. In order to ensure for reliable quantification of the transport that released corrosion inhibitor moving towards the defect is not reacting with corroding metal at the interface special PVB│PPy│Au-Glass model samples were utilized. The results indicate that Ce4+ is more effective than Ce3+ for reaching and passivating the defect. In addition, organic corrosion inhibitors (8-HQ, β-CD and L-Car) were found to be highly efficient in inhibiting the defective site. This is proposed to be due through a synergistic mechanism, which is based on an interaction of the passivating effect of these corrosion inhibitors and the passivating effect of polypyrrole. The synergistic mechanism shows astonishing passivation effects, resulting in anodic potential shifts of the corrosion potential of more than 600 mV. Concerning the main path for ionic transport, it was found that this occurs mainly through the matrix of the (partially) reduced polypyrrole. Hence, the transport of positive ions should be favored compared to the one of negative ions.

PENGARUH KONSENTRASI INHIBITOR KOROSI EKSTRAK KULIT PISANG KEPOK (Musa paradisiaca L) TERHADAP LAJU KOROSI BAJA KARBON API 5L PADA SUHU PERENDAMAN 40OC DAN 80OC

Research has been carried out on the effect of the concentration of Kepok banana peel extract as an inhibitor on API 5L carbon steel in 3% NaCl corrosive medium. API 5L carbon steel immersion was carried out for 7 hours with two variations of immersion temperature, namely 40 and 80 oC and five variations in the concentration of corrosion inhibitors, namely 0%, 2%, 4%, 6%, 8%. Corrosion rate testing was carried out using the weight loss method. The results showed that the largest corrosion rates at immersion temperatures of 40 and 80 oC were at 0% inhibitor concentrations, namely 60.91 mm / y and 86.91 mm / y. Meanwhile, the lowest corrosion rate was at the inhibitor concentration of 8% at immersion temperatures of 40 and 80 oC, namely 32.51 mm / y and 63.92 mm / y. The greatest effectiveness of corrosion inhibitors occurred at a concentration of 8% at immersion temperatures of 40 and 80 oC of 56.63%, and 26.44%. The results of the X-Ray Diffraction (XRD) characterization showed that the phase formed was pure Fe. Scanning Electron Microscopy (SEM) characterization showed uneven clusters and smaller size, holes and cracks were also less in 8% inhibitor at immersion temperature of 40 and 80 oC compared to inhibitor 0% at immersion temperature 40 and 80 oC.

Environmentally benign Prosopis juliflora extract for corrosion protection by sorption - Gravimetric, mechanistic and thermodynamic studies

Environmentally benign plant extract compounds have gained significant attention in the corrosion prevention applications due to their biodegradability and eco-friendliness. The adsorptive corrosion control action of Prosopis juliflora plant extract was investigated using differential mass change experiments and the mechanism was validated using Tafel and Nyquist plots. The effect of green corrosion inhibitor concentration (0–800 ppm) on corrosion rate at different solution temperatures (305.15, 310.15 and 315.15 K) in 1 M HCl was studied. The corrosion inhibitor exhibited monolayer surface coverage and confirmed by Langmuir isotherm (R2 > 0.970). The negative values of Gibbs free energy (<20 kJ/mol) proved the electrostatic interaction between the inhibitor and metal surface. The enhanced energy barrier for the corrosion process was confirmed by changes in Ea in the presence of biomass-based inhibitor on the mild steel surface. Electrochemical impedance study proved that the double layer capacitance (Cdl) decreased and the resistance increased with increase in corrosion inhibitor concentration. The surface modifications on the metal were observed using scanning electroscope imaging. ATR studies were conducted for functional group identification of the corrosion inhibitor.

Study on efficiency of corrosion inhibitors based on derivatives of isothiuronic salts

Metals play a pivotal role in industry; their use constantly grows. It is virtually impossible to find an industrial field without the use of metals and their alloys. However, owing to the quality degradation of metal during the operational process, corrosion appears not only on its surface but also under a coating, which leads to its destruction. To avoid this, corrosion inhibitors are necessary. Organic compounds have been widely used as corrosion inhibitors. Many organic corrosion inhibitors have been developed nowadays. In the literature, organic compounds comprising N, O, S and P heteroatoms are described, which reduce corrosion rate. The organic compounds are adsorbed on the metal surface, forming a thin layer. Adsorption occurs either through electrostatic interaction or, in some cases, the formation of covalent bonds. The work aimed to study isothiuronic salts as corrosion inhibitors to evaluate their protective properties using the polarisation curves method. Objects of research were isothiuronic compounds containing two active centres separated by saturated and unsaturated carbon bonds (structures 1-3). In structures 4-7, one isothiuronic fragment has different propylene substituting groups. It has been previously shown that these compounds can act as effective brightening agents when applying nickel coatings. A model solution with a density of 1.12 g/cm3 was prepared to study the corrosion inhibitors. The corrosion inhibitor concentration was 400 mg/L. Studies have shown that the compounds with two isothiuronic moieties do not always exhibit improved properties for inhibiting metal degradation in a corrosive environment. In particular, they showed worsening of the inhibiting properties for samples made of steel 20 and identical properties for that made of steel 3.

Electrochemical and surface analytical studies of transition metal bipyridine dicarboxylic acid complexes as corrosion inhibitors for a mild steel in HCl solution

The 2,2′-bipyridine-3,3′-dicarboxylic acid (bpda) and its transition metal complexes including Ni(bpda)2, Zn(bpda)2 and Mn(bpda)2, were synthesized and tested as corrosion inhibitors for a carbon steel in 0.5 M HCl solution by electrochemical tests and surface analyses. The electrochemical results indicate that the inhibition efficiencies increase with the concentration of corrosion inhibitors. The complexes exhibit higher inhibition efficiencies compared to the bpda ligand, among which Ni(bpda)2 is the most effective for inhibiting corrosion. The corrosion morphology observation further evidences the superior corrosion inhibition performance of the three complexes. Fourier transform infrared and X-ray photoelectron spectroscopy analyses confirm the spontaneous adsorption of all four inhibitors on the steel surface, and the adsorption analysis suggests a combined physisorption and chemisorption mechanism. Accordingly, the superior corrosion inhibition performance of the three complexes could be attributed to their good adsorption abilities.