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In this investigation, attempts have been made to study the corrosion inhibition properties of three new triazepine carboxylate compounds for mild steel in 1.0 M hydrochloric acid medium. The evaluation was carried out using mass loss, electrochemical impedance spectroscopy and polarization curves measurement. Impedance diagrams and Bode plots for uninhibited and inhibited systems were analyzed using Zview program. The fitted data observed trails in nearly the same pattern as the experimental results. It is showed that triazepine carboxylate compounds are very good inhibitors for mild steel corrosion in 1.0 M hydrochloric acid medium which act as mixed-type inhibitors. So, the inhibition efficiency was increased with inhibitor concentration in the order Cl–Me–CN > Me–CN > Cl–Me–CO2Et which depended on their molecular structures. Electrochemical impedance spectroscopy showed that all compounds act by the formation of a protective film at the metal surface. Surface analyses via SEM and Optical 3D profilometry were used to investigate the morphology of the steels before and after immersion in 1.0 M HCl solution containing inhibitors. The correspondence between inhibition property and molecular structure of the triazepine carboxylate compounds was investigated, using density functional theory (DFT). Experimental and DFT study was further supported by molecular dynamic simulations study.

Inhibitive performance of 3-methylquinoxaline-2 (1H) -thione denoted (MQ = S) on mild steel corrosion in 1.0 M H3PO4was investigated using electrochemical measurements. It is revealed that this product acts as an excellent corrosion inhibitor for mild steel in 1.0 M H3PO4where its inhibition reaches 93% at 5 × 10−4M and increases with immersion time. Potentiodynamic polarization curves indicated that this compound acts as a mixed-type inhibitor. In addition, the MQ = S has its inhibition at high temperature. It was found that the adsorption of this compound obeyed the Langmuir adsorption isotherm.

In this second part, the adsorption and thermodynamics properties of a polyacrylamide PA on corrosion inhibition of in 1.0 M HCl solution were analyzed by means of potentiodynamic polarization and electrochemical impedance spectroscopy techniques. Besides, the effects of temperature as well as the immersion time, on the inhibition efficiency, at 3 × 10−6mol L−1of PA, were also investigated. The adsorption data were modeled using six linearized forms of adsorption isotherms corresponding to Langmuir, Flory–Huggins, Temkin, Frumkin, Freundlich as well as the kinetic–thermodynamic model of El-Awady. The Langmuir model was first ruled out notwithstanding the highest value of linear regression coefficient and a slope close to unity. Secondly, it was found, according to both El-Awady and Flory–Huggins models, that exactly three molecules of water were replaced by one PA molecule. Thirdly, it was shown the presence of repulsive lateral interactions in the adsorbed inhibitory layer confirmed by the negative sign of the interaction parameters of Temkin and Frumkin isotherms. The effect of immersion period revealed significant improvement of the charge transfer resistance and accordingly the inhibiting efficiency which reach circa 96% after 6 h. The confrontation of thermodynamic (Kads, ΔrGads°) along with the kinetic parameters (A, Ea) showed that the adsorption of PA molecules onto C-steel surface involved both chemical and physical adsorption but predominantly chemisorption.

The chemical structure of a polyacrylamide (PA), synthesized by inverse emulsion polymerization, was confirmed by FTIR and 1H NMR. The experimental conditions were conducted to produce high molecular weight of 1.4 × 106g mol−1determined by both gel permeation chromatography and viscosity average molecular weight methods. The efficiency of PA was evaluated, on corrosion inhibition of C-steel in 1.0 M HCl solution, by means of electrochemical impedance spectroscopy, potentiodynamic polarization (PP), and mass-loss (ML) measurements, and a very good concordance was obtained from the three techniques. The inhibiting efficiency increased up to 4 × 10−6mol L−1and dropped down afterward. The PP curves revealed that PA was of mixed-type, influencing predominantly the anodic process. The electrochemical interface was satisfactorily modeled with the electrical circuit (RS + Qdl/Rct) using CPE(α,Q)reflecting one-time constant. This fact, testifying the dominant character of charge transfer control of the C-steel corrosion process, was well described in both Nyquist along with Bode diagrams which take into account the frequency dependence, justifying the suitable choice of the electrical circuit. The adsorption of PA involved both physical and chemical interactions of non-protonated and protonated molecules with a deeper discussion on the suitable sites of protonation. The performance of PA was maintained if not slightly ameliorated in a more aggressive medium such as 0.5 M H2SO4at 298 K. Two-time constants were needed to model the electrochemical interface (RS + Qdl/(Rct + RL/L)).

The adsorption and corrosion inhibition properties of three triazepines carboxylate substituted compounds, namely, ethyl 4,9-bis(4-chlorophenyl)-8-cyano-3-hydroxy-2,7-dioxo-1,2,5,7-tetrahydropyrido[1,2-b]triazepine-10-carboxylate (2Cl–Et), methyl 4,9-bis(4-chlorophenyl)-8-cyano-3-hydroxy-2,7-dioxo-1,2,5,7-tetrahydropyrido[1,2-b]triazepine-10-carboxylate (2Cl–Me), and ethyl 9-(4-chlorophenyl)-8-cyano-3-hydroxy-2,7-dioxo-4-(p-tolyl)-1,2,5,7-tetrahydropyrido[1,2-b]triazepine-10-carboxylate (Cl–Me–Et) on mild steel corrosion in 1.0 M of hydrochloride acid were investigated by using weight loss, electrochemical, and theoretical investigations. It is found that these compounds act as excellent inhibitors and their inhibition efficiencies follow the order: 2Cl–Me > 2Cl–Et > Cl–Me–Et, and they depend on the type of the substituent. In addition, the possible relations between the experimental and theoretical parameters were discussed. It is found that the theoretical parameters confirmed those obtained by experimental studies. Surface roughness morphology for mild steel before and after hydrochloric acid attack is investigated and discussed using 3D-profilometry images. The scanning electron microscope (SEM) images of the corrosion product confirmed the protection offered by triazepines carboxylate derivatives on the surface of the metal immersed in both media.

The electrochemical behavior of white cast iron in sulfamic acid was studied in the presence of hexadecyltrimethylammonium bromide as a corrosion inhibitor. The cooperative effect between counterions of sulfamic acid and CTAB was investigated as well as the impact of this phenomenon on the inhibition efficiency; for that purpose, gravimetric method, electrochemical impedance spectroscopy, potentiodynamic polarization curves and inductively coupled plasma spectrometry (ICP-OES) techniques were exploited. The CTAB molecule reveals remarkable qualities for the protection of white cast iron in sulfamic acid cleaning solutions. Sulfamate ions play a major role in this phenomenon by facilitating the attraction and adsorption of CTAB onto the surface of white cast iron. The inhibition efficiency remains almost stable (about 95%) for a concentration of 10−3M in CTAB. The critical micelle concentration of CTAB in the H2O/NH2SO3H system was investigated by the conductimetry method. The CTAB adsorption onto the cast iron surface was studied by Langmuir adsorption isotherms. The surface characterization by RDX and SEM showed a good anticorrosion protection and a lower surface roughness in the presence of CTAB.

The corrosion and scale behavior of copper in industrial cooling water system were investigated via electrochemical measurements, ionic chromatography, SEM/EDAX, and X-ray diffraction analyses. It was found that the studied water has a corrosion and scale character. The EDAX and XRD analyses indicated that the major corrosion and scale products were the CuO2and CaCO3, respectively. In addition, the middle Mueller–Hinton test was also employed to evaluate the development of microorganisms for copper in make-up water solution. It is noted that bacterial colonies appeared after immersion of samples in make-up water, indicating that this water develops bacterial colonization. Finally, the influence of some operating parameters on the corrosion and scale rate was studied. It was shown that the scale rate increases with pH, temperature, and the addition of chloride and sulfide ions. It was also found that the corrosion rate increases with temperature and chloride ions and decreases with pH and immersion time.

The inhibition efficiency of three substituted phenyltetrazole compounds, namely 5-(4-chlorophenyl)-1H-tetrazole (Cl-PT), 5-(4-methoxyphenyl)-1H-tetrazole (MO-PT), and 5-phenyl-1H-tetrazole (PT), for mild steel corrosion in 5.0 M HCl solution was\ investigated using weight loss measurements and electrochemical study. It is showed that these compounds are good inhibitors for mild steel corrosion in 5.0 M HCl solution which act as cathodic type inhibitors. So, the inhibition efficiency was increased with inhibitor concentration in the order of Cl-PT > MO-PT > PT which depended on their molecular structures. It is found also that these compounds toke its performance at different temperatures range from 298 to 328 K. In addition, the thermodynamic adsorption parameters at different concentrations were investigated and discussed. Finally, it is seen that the inhibition efficiency of the studied compounds increased with immersion time to reach a maximum at 12 h.

In this paper, we will study the effect of soil engineering properties’ relationship on metal degradation of two series of brass alloys (brass devices). These two types of brass are an α-brass and α+ βone. This work aims to specifying the best alloys which are recommended to be used in Azrou soil medium. This research paper was applied by using electrochemical impedance spectroscopy methods, polarization curves, scanning electron microscopy (SEM), and X-ray spectrometry microanalysis measurements. It was found that EC5 is the most resistant alloy between the three α-brasses and EC6 which is the most resistant alloy among the four α+ βbrasses in this soil type. The different alloy surfaces were examined by SEM, whereas the chemical composition was determined by EDAX analysis. Moreover, we have studied the role and effects of synergy on various additional elements which exist in different brasses and they are responsible for increasing the corrosion resistance.

The Cu–Zn (brass) materials are used extensively in potable water equipment including valves, taps, and accessories that are employed in a variety of industry sectors and household uses of water transport systems. The chemical element of these alloys such as Al, P, As and Fe. could have a significant impact on their corrosion resistance in potable water. In this context, a comparative investigation of the resistance of the corrosion of three α-Brasses has been studied by employing Potentiodynamic-Polarisation, Electrochemical-Impedance-Spectroscopy, and open circuit potential measurements. Further, both the dezincification factor “Z” and the standard dezincification test UNI EN ISO 6509 have been measured. Furthermore, the morphology of α-Brasses was investigated through SEM/EDS analysis and optical microscopy, and atomic force microscope (AFM) after the test. Moreover, analysis by X-ray diffraction (XRD) was conducted to explain crystalline composition forming on the surface after the experiment. The results achieved in this work have revealed that the presence of a double concentration of phosphorus and aluminum and a half percentage of iron enhances the corrosion resistance in comparison to brass which contains a double concentration of iron and a half percentage of phosphorus. Results have been confirmed by SEM/EDS and optical microscopy and XRD and Z-factor and AFM analysis.

The effect of eco-friendly 4,4′-(2-pyridylmethylene)bisphenol diacetate (DPMBP) for brass 62/38 in 200 ppm NaCl electrolyte was inspected by using electrochemical measurements, scanning electron microscopy (SEM) coupled with energy dispersive X-Ray (EDX) analysis, and theoretical investigations. It is obtained that DPMBP actions as a good inhibitor for brass 62/38 in 200 ppm NaCl where its inhibition touches 88 % at 5 × 10−4 M, and it reacts as a mixed-type inhibitor, affecting the anodic and cathodic process. The electrochemical impedance spectroscopy (EIS) results designated that the obtained plots were formed by two badly separated circles and their diameters rise with DPMBP contents, showing that it's acting on the brass 62/38 surface by the formation of a defensive film. Truly, it is obtained that the DPMBP particles reacted on the brass 62/38 area according to Langmuir adsorption isotherm. Furthermore, it is obtained that the inhibition efficiency of DPMBP is low temperature dependency. It is found also that the polarization resistance value of DPMBP growths with immersion time to attend 112.43 kΩ cm2at 24 h. The SEM/EDX analysis showed the creation of a protective layer and confirmed the electrochemical measurements results. Lastly, to take certain info around the adsorption properties of the considered DPMBP molecules, DFT calculations and MD simulation were used. It is obtained that the obtained η% of DPMBP for brass 62/38 corrosion is very compatible with the obtained experimental results.

Lavender oil is extracted from lavender herb, collected in the east region of Morocco (Tafoughalt) and tested as corrosion inhibitor for mild steel in 1 M HCl. The inhibiting effect was studied by weight loss measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. Polarisation measurements show that lavender oil essentially acts as a cathodic inhibitor. The natural oil reduced the overall corrosion current density. The protection efficiency was found to increase with oil content to obtain ca. 90% at only 2 g L-1and kept its inhibiting efficiency the same even at higher temperatures. The adsorption of lavender oil on mild steel followed the Langmuir's isotherm model. The thermodynamic parameters for inhibiting process were calculated and interpretation of the results was given.

To construct a clear idea about the reciprocal influence between Pseudomonas aeruginosa’s bacterium and the metal surface of Cu/Zn alloys [α-brass and (α + β)-brass]. This work presents a detailed study of the corrosion behavior of these alloys in drinking water and the electrochemical phenomena that occur during the formation of the biofilm. This study is based on the joint use of microbiological and electrochemical methods to reveal the effects generated between the bacterium and the metallic surface. This study was conducted by stationary electrochemical methods of potential monitoring and polarization curves, and trans-methods (electrochemical impedance spectroscopy) to evaluate the effect of the bacteria on the corrosion behavior of α-brass and (α + β)-brass alloys. The Inductively Coupled Plasma Spectroscopy method was used to monitor the concentration evolution of Cu2+and Zn2+ions as a function of time and to determine also the dezincification factors. The monitoring of the bacteria evolution on the surface is ensured by microbiological techniques (enumeration of viable bacteria adherent and total adherent). The Pseudomonas aeruginosa’s strain has a remarkable effect on the corrosion and dezincification of both alloys, this is due to the formation of the biofilm which blocks the formation of a film of protective oxides on the surface. However, its effect on α-brass is largely inferior to (α + β)-brass, this may be related to the surface composition and the simultaneous presence of certain elements such as Cu, Ni and Al.

Synergistic erosion-corrosion behavior of two types of brass, (α + β)-brass (CuZn36Pb2As) and lead-free α-brass (CuZn21Si3P) was studied in simulated drinking water. A jet device was employed with various impingement angles (15°, 30°, 45°, 75°, and 90°) and a velocity of 11 m/s, using the eroding particle (SiO2) of which concentration was 30 g/l. All tests were conducted in accordance with ASTM G119-09. Electrochemical Measurements and corrosion weight Loss tests showed that the maximum erosion-corrosion rate for both alloys occurred at an impingement angle of 45°. And the electrochemical corrosion rate increased with increasing the impingement angle and reached the maximal value at an angle of 90°. The interaction between corrosion and erosion could lead to a positive synergy effect representing 27% of total degradation (erosion-corrosion) for (α + β)-brass and 19% for α-brass. The total synergism was mainly an effect of corrosion on erosion, and the dominated regime was a synergistic effect at all impingement angles. The SEM/EDX showed for α-brass, erosive tracks, and some protective layers, and for (α + β)-brass, erosive tracks, craters, and deformed lips. After 1 h of erosion-corrosion tests, both alloys regenerated a protective layer at different impact angles. α-brass regenerated the protective oxide layer better than (α + β)-brass. α-brass is more resistant to erosion-corrosion than (α + β)-brass thanks to its chemical compositions and its mechanical characteristics, mainly hardness and yield strength.

Lavender oil is extracted from lavender herb, collected in the east region of Morocco (Tafoughalt) and tested as corrosion inhibitor for mild steel in 1 M HCl. The inhibiting effect was studied by weight loss measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. Polarisation measurements show that lavender oil essentially acts as a cathodic inhibitor. The natural oil reduced the overall corrosion current density. The protection efficiency was found to increase with oil content to obtain ca. 90% at only 2?g L-1and kept its inhibiting efficiency the same even at higher temperatures. The adsorption of lavender oil on mild steel followed the Langmuir's isotherm model. The thermodynamic parameters for inhibiting process were calculated and interpretation of the results was given. Utilisation de l'huile de lavande comme inhibiteur environnemental pour l'acier doux en milieu HCl 1 M. L'huile de lavande est extraite de l'herbe correspondante, collect?e dans la r?gion de l'oriental au Maroc (Tafoughalt) et test?e comme inhibiteur de la corrosion pour l'acier doux en milieu acide HCl 1?M. L'effet inhibiteur a ?t? ?tudi? par des mesures de perte de masse et le couplage des m?thodes ?lectrochimiques?; courbes de polarisation et spectroscopie d'imp?dance ?lectrochimique. Les mesures stationnaires montrent que l'huile de lavande agit essentiellement sur la branche cathodique. L'huile essentielle r?duit consid?rablement la densit? de courant de corrosion. L'efficacit? protectrice augmente avec la quantit? additionnelle de l'huile pour atteindre ca. 90?% ? 2?g L-1. L'efficacit? est maintenue ?lev?e m?me ? haute temp?rature. Le processus d'adsorption ? la surface de l'acier doux suit le mod?le de l'isotherme de Langmuir. Les param?tres thermodynamiques issus de l'effet inhibiteur de l'huile sont calcul?s et une interpr?tation des r?sultats obtenus est explicit?e.

Graphic abstract:

A new 2-(5-methyl-2-Nitro-1H-imidazol-1-yl)ethyl benzoate (IMDZ-B) was synthesized and characterized using elemental analyses, NMR and Fourier transform infra-red (FTIR) techniques. Its effect on brass corrosion in 1.0 M H3PO4solution was investigated by using electrochemical measurements coupled with X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). The polarization measurements showed that the IMDZ-B acts as a mixed type inhibitor. Indeed, it is found that the IMDZ-B compound is a very good inhibitor, which its inhibition efficiency increases with concentration to reach a maximum of 99.5% at 10−3 M. In addition, the obtained electrochemical parameters from impedance indicated that the IMDZ-B molecules act by adsorption on metallic surface. This adsorption was found to obey Langmuir's adsorption isotherm. However, the temperature effect on the performance of IMDZ-B was also studied. It is found that the IMDZ-B takes its performance at high temperature. In addition, the obtained kinetic and thermodynamic parameters showed that the IMDZ-B molecules act via two adsorption modes, physisorption and chemisorptions, and its process is endothermic and spontaneous. Finally, the XRD and SEM/EDX analyses confirmed the electrochemical obtained results.

The corrosion of four brasses EC1 and EC2 of (α + β) brass type while EC3 and EC4 are of α-brass type in the aggressive sandy soil collected in a suburban area of Essouira Morocco was studied. The original soil was characterized, and modified by adding the chloride ions or by increasing its moisture content. The corrosion behavior of these brasses in soil was investigated at ambient temperature using various electrochemical methods. The different alloy surfaces were examined by scanning electron microscopy, whereas the chemical composition was determined by EDS analysis. EIS measurements indicated that the corrosion rate of all brasses series increases with increasing the moisture content of the studied soil up to critical limit (30 wt%), then it starts to decrease with further increase of moisture content. It was found that the chemical composition of brass influences the corrosion rate, especially the presence of iron, Nickel and Arsenic. Furthermore, EC3 is always the most resistant among the other alloy even in a very aggressive environment containing the chloride ions with a concentration of 2%.