Composite thin films based on polycaprolactone-polyethylene glycol (PCL-PEG) polymeric blends employed in medical application, with convenient mechanical strength and corrosion behavior, controllable hydrophilicity/ wettability and degradability were deposited by dip coating technique. The present study analyzes long term in vitro degradation profile of simple and composite films in dynamic flux of simulated body fluid. The obtained biological results proved that the thin films stimulate and support tissue growth.We identify the effect of PEG incorporation on the biodegradation characteristics of more stable PCL. Static water contact angles measurement indicated that hydrophilicity of the composite films containing more PEG has improved considerably.

It has been shown that the degradation of PCL-PEG blends increase with a decreasing crystallinity of the PEG, and can be controlled by adjusting the component ratio of the blends.

It was found that the degradability of the polycaprolactone was improved by introducing a PEG component into it. The degradation of PCL -PEG copolymer increase with a decreasing crystallinity of the copolymer, and can be controlled by adjusting the component ratio of the copolymer.

Chloride induced corrosion of steel reinforcement is one of the main causes of deterioration of reinforced concrete structures. Cathodic protection (CP) of steel in concrete is a widely accepted repair technique to reduce or completely stop reinforcement corrosion. One possible method of cathodic protection is through the use of embedded galvanic (sacrificial) anodes, consisting of a zinc metal core surrounded by a precast alkali-activated cementitious mortar.

The design of a CP system based on embedded galvanic anodes is based on the required amount of zinc material and the throwing power of the anode (i.e. radius around the anode in which the steel achieves sufficient protection).

In this research the protection of steel reinforcement in concrete surrounding an embedded galvanic anode was evaluated through depolarisation measurements with internal and external reference electrodes. Based on these measurements, the throwing power of the galvanic anode was determined, taking into account the 100 mV depolarisation criterium (cf. EN ISO 12696:2016). Also, the influence of the amount of chloride contamination of the concrete and relative humidity and temperature of the environment on the throwing power was evaluated.

Results show a strong influence of the chloride contamination on the throwing power of the galvanic anodes, in the sense that a higher chloride concentration in the concrete matrix leads to a reduction of the throwing power. This reduction can be related to the more negative potential of corroding steel reinforcement compared to passive steel, thus leading to a lower driving potential for the galvanic reaction. Especially when the chloride concentration is higher than 1 m% vs cement mass, the throwing power is greatly reduced. Also, it was found that a higher relative humidity (RH) of the environment (and consequently a higher RH of the concrete) results in a higher throwing power.

Meryem Hrimla^a,⁎, Lahoucine Bahsis^a,b, Aziz Boutouil^a, My Rachid Laamari^a,⁎, Miguel Julve^c, Salah-Eddine Stiriba^a,c,⁎.

^a Laboratoire de Chimie Analytique et Moléculaire /LCAM, Université Cadi Ayyad, Faculté Polydisciplinaire de Safi, Sidi Bouzid. B.P. 4162, 46 000 Safi, Morocco
^b Département de Chimie, Faculté des Sciences d'El Jadida, Université Chouaïb Doukkali, B.P.:20, El Jadida 24000, Morocco
^c Instituto de Ciencia Molecular/ICMol, Universidad de Valencia, C/Catedrático José Beltrán 2, 46980, Valencia, spain.

⁎ Corresponding authors:
E-mail addresses: r.laamari@gmail.com (M.R. Laamari); stiriba@uv.es (S-E Stiriba); meryemhrimla.uca@gmail.com (M. Hrimla).

Abstract

The study of the corrosion inhibition of mild steel using organic inhibitors, mainly in an acid environment, is one of the main current research topics in the steel industry [1]. In this context, 1,2,3-triazoles are N-heterocyclic compounds containing a five-membered ring with three nitrogen atoms. Their derivatives are used in a wide variety of applications ranging from biology and pharmaceuticals to the development of large quantities used as corrosion inhibitors [2]; this minimizes the corrosion of metals and alloys, which is a serious problem worldwide [3]. The use of these additives is a significant advance due to their economical synthesis route and high inhibitory efficiency, as well as the presence of electron donors such as oxygen (O), nitrogen (N), sulfur (S) atoms, and conjugated groups in its structure to act as powerful inhibitors for the prevention of corrosion of metals by acids [4]. In the present work, the inhibition performance of the new flexible multidentate 1,2,3-triazole compound, namely 4-[1-(4-Methoxy-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-morpholine (MPTM) synthesized under the click chemistry strategy using the copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC). Its inhibitory effect was studied using a range of electrochemical methods such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) methods, and weight loss measurements. Also, to take into account the adsorption phenomenon of MPTM, the adsorption models of the reference compound were tested during the corrosion prevention process using Freundlich, Langmuir, and Temkin methodologies. Theoretical studies were used to rationalize the adsorption mechanism of the MPTM compound on the surface of mild steel.

References

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[2] Li, G., Field, J. A., Zeng, C., Madeira, C. L., Nguyen, C. H., Jog, K. V., Speed D, Sierra-Alvarez R.Sierra-Alvarez, R. Diazole and triazole inhibition of nitrification process in return activated sludge. Chemosphere, 241, 124993, 2020.

[3] Tisza, M., & Czinege, I. Comparative study of the application of steels and aluminium in lightweight production of automotive parts. International Journal of Lightweight Materials and Manufacture, 1(4), 229-238, 2018.

[4] Dehghani, A., Bahlakeh, G., Ramezanzadeh, B. A detailed electrochemical/theoretical exploration of the aqueous Chinese gooseberry fruit shell extract as a green and cheap corrosion inhibitor for mild steel in acidic solution. Journal of Molecular Liquids, 282, 366-384, 2019.

An effective solution for corrosion protection of metallic carbonyl iron (CI) substrates in strong saline environment (3 M KCl) is demonstrated in this work. A thin layer coating of graphene oxide (GO) sheets enhances the corrosion inhibition behavior of amino acids that are directly grafted on metallic iron surfaces. The combined effect of GO and the corrosion inhibiting layer such as para-aminobenzoic acid (PABA), glycine, or alanine drastically improves the corrosion inhibition efficiency, in comparison to any of the single-layer coating, without considerably increasing the coating layer thickness. The microscopic origin of the corrosion protection efficiency of these layers is explained by the physical arrangement of the inhibitor molecules and the integrity of the GO sheets. According to our results, although a single layer of alanine provides better corrosion protection than that of a single layer of glycine or PABA, an additional coating of GO sheets effectively enhances the corrosion protection efficiency multifold. This comes with a concomitant advantage that glycine is economically much cheaper than alanine. Hence, our study demonstrates an economical way to achieve excellent efficiency in corrosion inhibition for metallic surfaces, making our technology exceptional for their direct implementation in environmental and industrial applications.

Several aluminium (Al) based MPEAs are reported to exhibit excellent corrosion and pitting resistance. Owing to a scarcity of detailed physical analysis, mechanistic aspects of the passivity of aluminium (Al) based MPEAs have not been adequately described to date. The complex thermo-kinetic interfacial processes that govern the dissolution behavior of MPEAs are challenging to ascertain; and herein an in-situ atomic emission spectroelectrochemistry (AESEC) method was used to investigate dissolution and passivation behavior. Along with AESEC analysis, the formation and evolution of the passive films were studied using X-ray photoelectron spectroscopy (XPS), Mott-Schottky analysis and equilibrium thermodynamics.

The elementally resolved dissolution kinetics of a Ni-Fe-Cr-Mn-Co multi-principal element alloy (MPEA) was investigated by in-situ atomic emission spectroelectrochemistry (AESEC) coupled to electrochemical impedance spectroscopy (EIS). Potentiostatic AESEC-EIS experiments were conducted at open circuit potential and a passive potential in 2 M H2SO4 solution. Elemental Lissajous plot enabled to determine the elemental Tafel slopes of each alloying element suggesting that the different elemental oxidation rate would lead to a duplex oxide formation during passivation. Elementally resolved dissolution rates in spontaneous dissolution (elemental corrosion rates) were estimated by Stern-Geary equation with elemental Tafel slopes and polarization resistance obtained from EIS.

Acknowledgement: The research was primarily supported as part of the Center for Performance and Design of Nuclear Waste Forms and Containers (WastePD), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under award #DE-SC0016584. K. Ogle and the AESEC experiments were supported by the Agence Nationale de Recherche, grant # ANR-20-CE08-0031 (Tapas 2020).

Multi-principal element alloys (MPEAs) offer the possibility of considerable degrees of freedom in the choice of alloying elements to produce either single or multi-phase solid solution alloys. A wide range of material properties, sometimes unique, have been observed based on the alloying elements selected and microstructures developed. However, a structure, composition, and processing paradigm governing the corrosion properties of MPEAs has not yet emerged. The quest for superior corrosion properties requires understanding of the fate of each element during corrosion and its subsequent functions. These issues are discussed with the goal of accelerating the understanding of the corrosion behavior in this class of materials.

The unique corrosion characteristics of a multi-principal element alloy with the composition Ni38Fe20Cr21Mo6W2Ru13 (referred to as MPEA1) have been reported. Ruthenium, present in the alloy ~20% by weight, is believed to play a key role arresting localized corrosion of alloy in harsh Cl-containing solutions. In this research, Ru in MPEA1 was substituted with commodity elements such as Mn, Al and Cu with a view to lower the cost of the alloy while causing a minimal drop in the corrosion resistance. Based on thermodynamic predictions, five candidate compositions analogous to MPEA1 were conceptualized and fabricated using vacuum arc melting. The solutionized, single-phase versions of all five candidate alloys were found to resist localized corrosion in 0.6 M NaCl at ambient temperature. While all five alloys show minimal hysteresis during cyclic potentiodynamic polarization experiments, one alloy that contains Mn exhibited metastable current transients but did not pit. Despite forming oxide films of similar thickness and quality as evaluated using single-frequency impedance methods, X-ray photoelectron spectroscopy (XPS) revealed constituent elements to dissolve in a non-congruent fashion. A clear Cr enrichment was not evident after potentiostatic polarization intended to passivate the alloys. The role of constituent elements in influencing the oxide formation process was indicated by a quantitative treatment of the XPS data.

This paper compiles aspects on the corrosivity of hydrocarbon fluids in oil pipelines. Oil pipelines carry complex mixtures of hydrocarbons, water, gases, and miscellaneous chemicals that, in relation to the physico-chemical and flow conditions, drive internal corrosion in a variety of ways. The paper highlights the water-oil emulsions and multiphase flow regimes, wettability of metal surface, corrosivity of aqueous phase in crude oil, composition of the aqueous phases in hydrocarbon fluids, roles of O₂, CO₂, sulfur and H₂S in the hydrocarbon fluids, and influence of oil chemistry on the corrosivity of the aqueous phase.

This paper outlines the up-to-date methods of internal pipeline corrosion control. The methods are based on controlling the amounts of water phase and gaseous phases that dissolve in water (including CO₂, O₂, and H₂S), as well as on cleaning, inhibition, and optimized design. The paper presents the feasibility of environmental control, which covers degasification and dehydration, pipe cleaning, which covers pigging and internal coating, and inhibitors. The paper discusses the influence of the operation conditions of consideration to a corrosion control method.