Performance and Application of Double-layered Microcapsule Corrosion Inhibitors

Double-layered microcapsule corrosion inhibitors were developed by sodium monofluorophosphate as the core material,polymethyl methacrylate as the inner wall material,and polyvinyl alcohol as the outer wall material combining the solvent evaporation method and spray drying method.The protection by the outer capsule wall was used to prolong the service life of the corrosion inhibitor.The dispersion,encapsulation,thermal stability of microcapsules,and the degradation rate of capsule wall in concrete pore solution were analyzed by ultra-deep field microscopy,scanning electron microscopy,thermal analyzer,and sodium ion release rate analysis.The microcapsules were incorporated into mortar samples containing steel reinforcement,and the effects of double-layered microcapsule corrosion inhibitors on the performance of the cement matrix and the actual corrosion-inhibiting effect were analyzed.The experimental results show that the double-layered microcapsules have a moderate particle size and uniform distribution,and the capsules were completely wrapped.The microcapsules as a whole have good thermal stability below 230 ℃.The monolayer membrane structure microcapsules completely broke within 1 day in the simulated concrete pore solution,and the double-layer membrane structure prolonged the service life of the microcapsules to 80 days in the simulated concrete pore solution before the core material was completely released.The mortar samples containing steel reinforcement incorporated with the double-layered microcapsule corrosion inhibitors still maintained a higher corrosion potential than the monolayer microcapsule corrosion inhibitors control group at 60 days.The incorporation of double-layered microcapsules into the cement matrix has no significant adverse effect on the setting time and early strength.

Evaluation of self-healing properties of inhibitor loaded nanoclay-based anticorrosive coatings on magnesium alloy AZ91D

This study emphasizes on the evaluation and comparison of the anticorrosive properties of sol-gel coatings with and without inhibitor loaded nanocontainers.In this case,naturally available clay nanotubes(halloysite)were loaded with cationic corrosion inhibitors Ce 3+/Zr 4+.These nanocontainers were dispersed in hybrid organic-inorganic sol-gel matrix sol.Coating was applied on magnesium alloy AZ91D using the sols containing modified and unmodified nanocontainers employing the dip coating method and cured at 130℃for 1 h in air.Corrosion resistance of coated/uncoated substrates were analyzed using electrochemical impedance spectroscopy,potentiodynamic polarization and weight loss measurements after exposure to 3.5 wt%NaCl solution for varying time durations between 24 h to 120 h.Self-healing ability of coatings was evaluated by micro-Raman spectroscopy after 120 h exposure to 3.5 wt%NaCl solution.Coatings generated after dispersion of corrosion inhibitor loaded clay in hybrid sol-gel matrix have shown more promising corrosion resistance when compared to just the sol-gel matrix coatings,after prolonged exposure to corrosive environment.

Design of self-healing PEO-based protective layers containing in-situ grown LDH loaded with inhibitor on the MA8 magnesium alloy

The high corrosion rate of magnesium and its alloys in chloride-containing solution significantly reduces the potential of this material for diverse applications.Therefore,the formation of a smart protective coating was achieved in this work to prevent degradation of the MA8 magnesium alloy.A porous ceramic-like matrix was obtained on the material by plasma electrolytic oxidation(PEO).Further surface functionalization was performed using layered double hydroxides(LDH) served as nanocontainers for the corrosion inhibitor.Several methods of LDH intercalation with benzotriazole(BTA) were proposed.The composition and morphology of the formed coating were studied using SEM-EDX analysis,XRD,XPS,and Raman microspectroscopy.The corrosion behavior of the coated samples was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization.The corrosion rate was estimated using volumetry and gravimetry methods.The formed composite coating provides the Mg alloy with the lowest corrosion activity(|Z|_(f)=0.1 Hz)=8.48·10^(5) Ω·cm^(2),I_(c)=1.4·10^(-8)A/cm^(2),P_(H)=0.21 mm/year) and improves the protective properties of the PEO-coated sample(|Z|_(f)=0.1 Hz)=8.37·10^(3) Ω·cm^(2),I_(c)=4.1·10^(-7)A/cm^(2),P_(H)=0.31 mm/year).The realization of the self-healing effect of the inhibitor-containing LDH/PEO-coated system was studied using localized electrochemical methods(SVET and SIET) with two artificial defects on the surface.A mechanism involving three stages for the active corrosion protection of the alloy was proposed.These findings contribute to the follow-up work of developing modified LDH/PEO-based structures that promote the Mg alloy with high corrosion resistance,superior electrochemical performance for applications in various fields of industry and medicine.

Experiment and numerical simulation of distribution law of waterbased corrosion inhibitor in natural gas gathering and transportation pipeline

The transmission medium of natural gas gathering and transportation pipelines usually contains cor-rosive gases,which will cause serious corrosion on the inner wall of the pipelines when they coexist with water.Therefore,it is necessary to add corrosion inhibitor to form a protective film to protect the pipeline.The distribution of corrosion inhibitors in a gathering and transportation pipeline in Moxi gas field was studied by combining experiment and simulation.The Pearson function was used to calculate the experimental and simulation results,and the correlation was more than 80%,indicating a high degree of agreement.The simulation results show that:①The larger the pipe angle,filling speed and gas flow rate,the smaller the particle size,the better the distribution of corrosion inhibitor particles in the pipe.The filling amount will affect the concentration,but the distribution trend is unchanged;②A method to determine the filling mode based on the loss was proposed,and for this pipeline,the loss of corrosion inhibitor was determined to be 5.31×10^(-3) kg/s,and the flling amount was recommended to be adjusted to 2o L/h,which has certain guiding significance for the actual flling strategy of pipeline corrosion inhibitor.

Effect of Corrosion Inhibitor Used in Surface Treatment on the Anticorrosive Performance of an Epoxy Paint System

The mechanism of corrosion is mainly sustained by an electrochemical process, in which anodic and cathodic reactions take place, keeping their kinetics alive by electrons and ions fluxes. Several specific conditions can accelerate corrosion processes. When studying anticorrosive coatings, one of them is the contamination of metallic surface by soluble salts prior to coating, leading to premature failure of the paint system due to corrosion between the metallic surface and the coating. So the surface preparation step prior to coating is a procedure of great importance to the coating anticorrosive performance. The aim of this step is to clean the surface by removing visible and non-visible contaminants. Usually, wet abrasive blasting methods are the most efficient ones to achieve the latter objective, because they may clean the surface, create a surface roughness and also remove the non-visible contaminants, as they use water as a media. On the other hand, evaporation of water after blasting may create flash rust and to avoid this, it is common to use corrosion inhibitors in the water of wet blasting methods. In this paper, the use of sodium tetraborate (borax) as a corrosion inhibitor in wet abrasive blasting is discussed. Electrochemical measurements and mass loss tests show that a borax content of 1% in a saline solution has the best inhibitory action over carbon steel and zinc surfaces, allowing postponing for the painting step some time. However, residual borax left on the surface generated blistering and corrosion under coating, during accelerated corrosion test in a humidity condensation chamber. Electrochemical impedance spectroscopy confirmed that borax accelerated the permeation of water through the coating, downgrading the anticorrosive performance of the paint system.

In-situ construction of grass-like hybrid architecture responsible for extraordinary corrosion performance: Experimental and theoretical approach

Despite the engineering potential by the co-existence of inorganic and organic substances to protect vulnerable metallic materials from corrosive environments,both their interaction and in-situ formation mechanism to induce the nature-inspired composite remained less understood.The present work used three distinctive mercaptobenzazole(MB)compounds working as corrosion inhibitors,such as 2-mercaptobenzoxazole(MBO),2-mercaptobenzothiazole(MBT),and 2-mercaptobenzimidazole(MBI)in a bid to understand how the geometrical structure arising from O,S,and N atoms affected the interaction toward inorganic layer.MB compounds that were used here to control the corrosion kinetics would be interacted readily with the pre-existing MgO layer fabricated by plasma electrolysis.This phenomenon triggered the nucleation of the root network since MB compounds were seen to be adsorbed actively on the defective surface through the active sites in MB compound.Then,the molecule with twin donor atoms adjacent to the mercapto-sites affected the facile growth of the grass-like structures with‘uniform’distribution via molecular self-assembly,which showed better corrosion performance than those with having dissimilar donor atoms with the inhibition efficiency(η)of 97%approximately.The formation mechanism underlying nucleation and growth behavior of MB molecule was discussed concerning the theoretical calculation of density functional theory.

5-methyl-1H-benzotriazole as potential corrosion inhibitor for electrochemical-mechanical planarization of copper

According to the electrochemical analysis, the corrosion inhibition efficiency of 5-methyl-lH-benzotriazole （m-BTA） is higher than that of benzotrizaole （BTA）. The inhibition capability of the m-BTA passive film formed in hydroxyethylidenediphosphonic acid （HEDP） electrolyte containing both m-BTA and chloride ions is superior to that formed in m-BTA-alone electrolyte, even at a high anodic potential. The results of electrical impedance spectroscopy, nano-scratch experiments and energy dispersive analysis of X-ray （EDAX） indicate that the enhancement of m-BTA inhibition capability may be due to the increasing thickness of passive film. Furthermore, X-ray photoelectron spectrometry （XPS） analysis indicates that the increase in passive film thickness can be attributed to the incorporation of C1 into the m-BTA passive film and the formation of [Cu（I）CI（rn-BTA）], polymer film on Cu surface. Therefore, the introduction of C1- into m-BTA-containing HEDP electrolyte is effective to enhance the passivation capability of m-BTA passive film, thus extending the operating potential window.

Active corrosion protection of super-hydrophobic corrosion inhibitor intercalated Mg-Al layered double hydroxide coating on AZ31 magnesium alloy

Magnesium alloys,the advanced lightweight structural materials,have been successfully applied in the manufacturing field.Unfortunately,their poor corrosion resistance restrains the potential wide applications.In this work,anti-corrosion coatings were fabricated via the insitu growth of the corrosion inhibitors intercalated magnesium-aluminum layered double hydroxide(Mg-Al LDH)on AZ31 magnesium alloy and then post-sealing it by a super-hydrophobic coating.SEM,XRD,EDS,FTIR,XPS and contact angle test were conducted to analyze physical/chemical features of these coatings.Potentiodynamic polarization curves and electrochemical impedance spectroscopy were recorded to assess the anti-corrosion performance of prepared coatings.Surprisingly,Mg-Al LDH with molybdate intercalation and lauric acid modification achieves the excellent corrosion inhibition performance(99.99%)due to the multicomponent synergistic effect such as the physical protection of Mg-Al LDH,the corrosion inhibition of molybdate and super-hydrophobic properties of lauric acid.This work presents a scientific perspective and novel design philosophy to fabricate the efficient anti-corrosion coating to protect magnesium alloys and then expand their potential applications in other field.

Electrochemical and analytical characterization of three corrosion inhibitors of steel in simulated concrete pore solutions

Corrosion inhibitors for steel, such as sodium phosphate （Na3PO4）, sodium nitrite （NaNO2）, and benzotriazole （BTA）, in simulated concrete pore solutions （saturated Ca（OH）2） were investigated. Corrosion behaviors of steel in different solutions were studied by means of corrosion potential （Ecorr）, linear polarization resistance （LPR）, electrochemical impedance spectroscopy （EIS）, and potentiodynamic polarization （PDP）. A field emission scanning electron microscope （FESEM） equipped with energy dispersive X-ray analysis （EDXA） was used for observing the microstructures and morphology of corrosion products of steel. The results indicate that, compared with the commonly used nitrite-based inhibitors, Na3PO4 is not a good inhibitor, while BTA may be a potentially effective inhibitor to prevent steel from corrosion in simulated concrete pore solutions.

Preparation and characterization of a chitosan-based low-pH-sensitive intelligent corrosion inhibitor

A chitosan （CS）-based low-pH-sensitive intelligent corrosion inhibitor was prepared by loading a pH-sensitive hydrogel with benzotriazole （BTA）; the pH-sensitive hydrogel was synthetized by crosslinking CS with glutaraldehyde （GTA）. Analysis by Fou- tier-transform inflared （FT-IR） spectroscopy showed that Schiff reactions occurred between amino and aldehyde groups. The swelling abil- ity of the hydrogel was investigated using a mass method, and it was observed to swell more in an acidic environment than in an alkaline en- vironment. The hydrogel＇s loading capacity of BTA was approximately 0.377 g·g ^-1, and its release speed was faster in an acidic environment than in an alkaline environment because of its swelling behavior. The corrosion inhibition ability of the intelligent inhibitor was tested by immersion and electrochemical methods. The results showed that after 4 h of immersion, the polarization resistance （Rp） value of copper with the intelligent inhibitor was approximately twice of that of copper with BTA, indicating that the intelligent inhibitor could effectively prevent copper from corroding.

Effectiveness of inhibitors in increasing chloride threshold value for steel corrosion

This investigation was aimed at evaluating the effectiveness of corrosion inhibitors in increasing the chloride threshold value for steel corrosion. Three types of corrosion inhibitors, calcium nitrite （Ca（NO2）2）, zinc oxide （ZnO）, and N,N＇-dimethylaminoethanol （DMEA）, which respectively represented the anodic inhibitor, cathodic inhibitor, and mixed inhibitor, were chosen. The experiment was carried out in a saturated calcium hydroxide （Ca（OH）2） solution to simulate the electrolytic environment of concrete. The inhibitors were initially mixed at different levels, and then chloride ions were gradually added into the solution in several steps. The open-circuit potential （Ecorr） and corrosion current density （lcorr） determined by electrochemical impedance spectra （EIS） were used to identify the initiation of active corrosion, thereby determining the chloride threshold value. It was found that although all the inhibitors were effective in decreasing the corrosion rate of steel reinforcement, they had a marginal effect on increasing the chloride threshold value.

Effects of Corrosion Inhibitors on Lubrication Performance of Rolling Oil for Copper Foil

The 2,5-bis（ethyldisulfanyl）-l,3,4-thiadiazole （T561）, benzotriazole （BTA）,1-N, N-bis （2-ethylhexyl） aminomethyl-4-methyl-lh-benzotriazole （IRGAMET39） and I-IN, N-bis （2-ethylhexyl） aminomethyl] methyl benzotriazole （TT- LX） have been evaluated as corrosion inhibitors used in rolling oil for cold rolling of copper foil. The MRS-10A four-ball friction and wear tests have been carried out to compare their tribological properties, and the lubricating performance of rolling oils has been studied through rolling experiments. The oil sample containing IRGAMET 39 has the same PB value as that one containing T561, with the coefficient of friction increased by 35.6% and wear scar diameter decreased by 4%. The minimum rolling gauge has been studied after rolling lubrication, but the results show that inhibitors have no effect on it. Scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS） analyses have indicated that the inhibitor is adsorbed on the copper surface to prevent copper from being corroded easily. In addition, the LEXT OLS4000 laser confocal microscopy has been used to observe the foil surface which shows that the streaks of foil surface are clear, the scratches are shallow and the surface failure is improved effectively.

New Naturally Occurring Product Extract as Corrosion Inhibitor for 316 Stainless Steel in 5% HCl

Medipolymorphol, a new sterol isolated from the whole plant of Medicago polymorpha Roxb was used as corrosion inhibitor for 316 stainless steel in 5% HCI at room temperature. Electrochemical techniques have been found to be reliable in evaluating corrosion characteristics of the system. Several techniques have been used including Tafel, linear polarization, potentiodynamic polarization, and open circuit potential (OCP) studies. The additives simultaneously deaccelerated the anodic process, intensified the cathodic process and provided a stable passive state, giving good inhibition efficiencies to stainless steel electrodes. In addition, adsorption isotherm have been fitted for the inhibitor under investigation.

Effect of Schiff base as corrosion inhibitor on AZ31 magnesium alloy in hydrochloric acid solution

Schiff base derived from the condensation reaction of analar grade 1-amino-2-naphthol 4-sulphonic acid with cinnamaldehyde was prepared under microwave condition.The Schiff base was analysed by infrared spectroscopy.This Schiff base as a corrosion inhibitor of AZ31 magnesium alloy in 0.05 mol/L HCl solution was studied.The inhibition effect of the Schifif base compound（4Z）-4-（3-phenyl allylidene amino）-3-hydroxy naphthalene-1-sulfonic acid（AC） on AZ31 magnesium alloy corrosion was studied using mass loss,potentiodynamic polarization technique,electrochemical impedance spectroscopy methods.The potentiodynamic polarization curve shows that Schiff base AC inhibits both anodic and cathodic reactions at all concentration,which indicates it is a mixed type inhibitor.EIS results indicate that as the additive concentration is increased,the polarization resistance increases whereas double-layer capacitance decreases.The adsorption of AC on the AZ31 magnesium alloy surface in 0.05 mol/L HCl obeys the Langmuir adsorption isotherm.

Release rate kinetics of corrosion inhibitor loaded halloysite nanotube-based anticorrosion coatings on magnesium alloy AZ91D

Halloysite nanotubes were used as nanocontainers to hold corrosion inhibitors such as Ce^(3+)-Zr^(4+),2-mercaptobenzothiazole and 8-hydroxyquinoline in their lumen.An acid assisted etching of the nanotubes was carried out with a view to increase the lumen diameter and thereby,increase the amount of loading of the corrosion inhibitor.The morphology of as-received and etched halloysite nanotubes was ob-served using TEM analysis.The loading of corrosion inhibitors was confirmed using SEM-EDS and BET analysis.Polymeric microcapsules were used as capping agents for the ends of the loaded HNTs following which,they were dispersed into a hybrid sol-gel silica matrix.Dip coating method was used to generate coatings on AZ91D substrates followed by heat treatment at 130℃ for 1 h.The release rate kinetics of corrosion inhibitors from as-received and etched nanotubes was investigated in buffer solutions of 3.5 wt%NaCl at different pH.The release mechanism of corrosion inhibitors from the HNT lumen was validated using various semi-empirical models.Coatings were also evaluated for their corrosion protection ability using electrochemical techniques after exposure to 3.5 wt%NaCl solution for 120 h.Coatings generated using Ce^(3+)-Zr^(4+)loaded into as-received halloysite nanotubes have shown more effective corrosion protection when compared to other corrosion inhibitors after 120 h exposure to the corrosive medium.

Adsorption isotherm mechanism of amino organic compounds as mild steel corrosion inhibitors by electrochemical measurement method

The inhibition ability of 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol （APTT）, ethylenediaminetetra-acetic acid （EDTA） and thiourea （TU） for mild steel corrosion in 1.0 moFL HC1 solution at 30 ℃ was investigated. Tafel polarization and electrochemical impedance spectroscopy （EIS） were used to investigate the influence of these organic compounds as corrosion inhibitors of mild steel in 1.0 mol/L HC1 solution at 30 ℃. The inhibition mechanism was discussed in terms of Langrnuir isotherm model. Results obtained from Tafel polarization and impedance measurements are in a good agreement. The inhibition efficiency increases with the increase of the inhibitor concentration. The adsorption of the inhibitors on the mild steel surface follows Langmuir adsorption isotherm and the free energy of adsorption AGads indicates that the adsorption of APTT, EDTA, and TU molecules is a spontaneous process and a typical chemisorption.

A modified method for evaluation of materials containing volatile corrosion inhibitor

A systematic research on a modified method that was developed to evaluate the effectiveness of volatile corrosion inhibitor(VCI) materials was carried out. The metal specimen in size of 50mm×25mm×2mm was level mounted on the top of a beaker by transparent adhesive tape and the assembly was placed in a constant temperature water bath and kept at approximately 40℃ to accelerate the vaporization of VCI and distilled water, which was placed at the bottom of the beaker at the same time. The experimental results show that the reproducibility of rust appearance and corrosion rate calculated by specimen’s mass loss is perfect. The outstanding characteristic of the rust appearance based on different VCI formula is discovered that is very important in studying the mechanism of VCI and the synergism of chemical reagent. The accelerated ratio is increased greatly as compared with the traditional method and the value is approximately 15 as compared with Shijiazhuang atmospheric environment corrosion test. The modified method is suitable for formula screening test and quick effectiveness evaluation of VCI materials.

Eco-friendly corrosion inhibitor from Pennisetum purpureum biomass and synergistic intensifiers for mild steel

Extracts of elephant grass （Penniseturn purpureum） blended with some intensifier halides like ammonium chloride （AMC） and potassium iodide （PTI） were investigated as corrosion inhibitor for mild steel. The corrosion process was monitored in 3.5% HCI by mass loss and electrochemical techniques at 30, 40, 50, 60 and 90 ℃. Addition of AMC and PTI increased the inhibition efficiency with the highest inhibition efficiency obtained with PTI blend- ed extract. The blends behaved as mixed type inhibitors and were spontaneously adsorbed on mild steel surface in exothermic nature. Synergistic parameters of the intensifier ions revealed cooperative effect. Kinetic data treatment indicated increase in energy barrier by intensifier ions. The results demonstrate that elephant grass extract blended with halide ions can act as alternative ecofriendly inhibitor for mild steel at elevated temperatures.

A time-saving method to assess the efficiency of corrosion inhibitors by electro osmosis

The corrosion inhibitor is one of the most important technologies to enhance the durability of steel-reinforced concrete. A kind of time-saving method was developed to assess the inhibitor efficiency by using a 32 V electric field to accelerate chloride ion migration in concrete. Potentiodynamic polarization scanning test was used to evaluate the corrosion states. The comprehensive efficiency of an inhibitor should be assessed in two aspects： resistance to chloride ion permeability and inhibiting efficiency. The specimens with different mixing amount of sodium nitrite and migration corrosion inhibitors were used to verify the accuracy and reliability of this method. The results show the differences in inhibiting efficiency of the inhibitors clearly, indicating the reliability of this time-saving method.

Capsella bursa-pastoris extract as an eco-friendly inhibitor on the corrosion of Q235 carbon steels in 1 mol·L^(-1) hydrochloric acid

The corrosion inhibition effect of Capsella bursa-pastoris extracts(CBE) for Q235 carbon steels in 1 mol·L-1hydrochloric acid solution was studied using electrochemical methods, environmental scanning electron microscopy(SEM) and Raman microscopy analysis. The polarization plots indicate that CBE serves as an effective, mixedtype inhibitor. Linear polarization resistance shows that increasing CBE concentration and temperature results in increased inhibition ef ficiency. The highest inhibition ef ficiency can reach 97% when adding 60 mg·L-1CBE,which is better than some reported plant extracts under the similar environment. The adsorption of CBE molecules is found to obey the Langmuir adsorption isotherm. Some thermodynamic and kinetic parameters for the adsorption process, such as the adsorption equilibrium constant(K), free energy of adsorption(ΔG ads), activation energy of corrosion reaction(E a) and the heat of adsorption(Q ads), are calculated and discussed. SEM and Raman microscopy analysis also demonstrate the formation of a CBE inhibition film on the metal surface.