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Evaluation of the Corrosion Inhibition Capability of Mild Steel Coated with a ZnO-Ni/PVDF Nanocomposite in a Simulated Concrete Pore Solution: An Electrochemical Investigation and Numerical Simulation
Abstract
Corrosion, which damages the rebar, is one of the main issues faced by reinforced concrete. In this study, a PVDF binder was combined with Zinc oxide and Nickel to increase the corrosion resistance of mild steel. The improved coating was tested using a simulated concrete pore solution. Changes in the characterization of the coating due to corrosion were evaluated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) at the beginning and end of the process. The corrosion inhibition capacity was evaluated via open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potential polarization experiments. The experimental findings demonstrate that the mild steel plate coated with a compound consisting of 0.75ZnO-0.25Ni/PVDF has exceptional corrosion resistance properties. The electrochemical tests were verified by an accelerated gravimetric test, which produced equivalent results and showed that the 0.75ZnO-0.25Ni/PVDF composites had an 87.47% corrosion inhibition capability. The electrochemical findings will serve as boundary conditions in COMSOL to model the coating and evaluate its effectiveness in a concrete rebar environment. The plots obtained from COMSOL include the electrolyte potential, electrolyte current density, and electrode potential. These results were compared for different samples, and the final result showed that the 0.75ZnO-0.25Ni/PVDF coating had the highest corrosion inhibition efficiency in a concrete rebar environment.
The corrosion performance of type 2101 lean duplex stainless steel (LDSS) after different solution annealing heat treatments is investigated. The austenite to ferrite phase ratios and morphologies are correlated to their localised corrosion responses, with the application of bipolar electrochemistry providing access to pit nucleation and growth kinetics. The propagation of pitting corrosion via selective dissolution of the ferrite phase is observed, pointing towards a direct effect of ferrite morphology on pit shape. The corrosion behaviour of solution heat treatments are compared and ranked, providing information for improving and optimising the corrosion resistance of LDSS 2101 microstructures.
In this work, we have developed a pipeline model made of 316 stainless steel considering the pipeline is subjected to a marine corrosive environment (seawater) and investigated pitting corrosion behaviour inside the pipeline with the help of COMSOL Multiphysics software. The extent of pitting corrosion was investigated by examining the electrochemical parameters such as electrolyte potential and electrolyte current density and explored the effect of variation in number of pits on the corrosion behaviour. Electrolyte potential distribution reveals that electrolyte potential variation along the pit surface is small and the value found to be highest at the pit- electrolyte interface. Thus, confirming that the pit electrolyte interface is more susceptible to corrosion. Electrolyte current density distribution showed that electrolyte current density value is highest at the pit, which is 314 A/m2 in case of single 3-D pit suggesting that the pit surface corroded heavily. In the case of multi-pit electrolyte current density distribution, the electrolyte current density computed to be 171 A/m2 and 106 A/m2 in double and triple pits, respectively. The obtained current density values have been used to calculate corrosion rate with the help of Faraday’s law. The multi-pits models are showing the corrosion rate of 195.7 mm/year and 121.3 mm/year for double and triple pit, respectively, which are comparatively lower than that of single pit (corrosion rate of 359.3 mm/year) due to increase in the area of anode surface.
ZnO-NiO nanocomposite with epoxy coating on mild steel has been fabricated by the sol–gel assisted method. The synthesized sample was used to study corrosion protection. The analysis was performed by electrochemical impedance spectroscopy in 3.5% NaCl solution. The structural and morphological characterization of the metal oxide nanocomposite was carried out using XRD and SEM with Energy Dispersive Absorption X-ray (EDAX) analysis. XRD reveals the ZnO-NiO (hexagonal and cubic) structure with an average ZnO-NiO crystallite size of 26 nm. SEM/EDAX analysis of the ZnO-NiO nanocomposite confirms that the chemical composition of the samples consists of: Zn (8.96 ± 0.11 wt.%), Ni (10.53 ± 0.19 wt.%) and O (80.51 ± 3.12 wt.%). Electrochemical Impedance Spectroscopy (EIS) authenticated that the corrosion resistance has improved for the nanocomposites of ZnO-NiO coated along with epoxy on steel in comparison to that of the pure epoxy-coated steel.
Now a day the more interesting and attracting point in research area is synthesis of nanoparticles with specific properties. Due to unique properties of oxide of nanoparticles achieve great attention in research areas. It is widely used as solar energy conversion, catalysis, varistors, gas sensors, non linear optics etc. ZnO nanostructures obtained a great attention in the research area because ZnO has large band gap. There are many different methods for synthesis of ZnO nanoparticles such as sol-gel method, chemical vapor decomposition, thermal decomposition, hydrothermal method etc. Among this method sol-gel method is the best for the preparation of ZnO nanoparticle. Fabrication of nanomaterial by sol gel method is simple and also its have advantage to control the size of material and morphology study of the material. The main objective of this paper is synthesis of ZnO nanoparticle by sol-gel method and studies its characterization. In this zinc acetate used as precursor, methanol as solvent, NaOH used as medium. The obtained ZnO nanoparticles are homogeneous and consistent in size corresponds to the XRD result that exhibit good crystallinity .ZnO nanoparticles are successfully synthesized by sol gel method. The obtained ZnO nanoparticles are characterized by XRD, SEM, and UV-visible
This study investigated the impact of the grain size of low carbon steel on its electrochemical behavior in a simulated concrete pore solution. Specimens with three grain sizes were used: as-received; coarse, with grains approximately 2 times larger than those in the as-received steel; and fine, with grains approximately half the size of those in as-received specimens. Specimens were immersed in a chloride-free pore solution for 10 days and then 3% by weight NaCl was added to the solution. The specimens were then kept in the chloride-contaminated solution for 60 days. The corrosion behavior of the specimens was evaluated by different electrochemical measurement techniques. Results showed that fine specimens passivated first, followed by the coarse and as-received specimens. However, in chloride-contaminated pore solution, the as-received specimens corroded more, followed by the fine and coarse specimens. In fact, the coarse specimens remained passive after 60 days of exposure to the chloride-contaminated pore solution.
The effect of zinc oxide on the corrosion inhibition of mild steel embedded in concrete in 3.5% sodium chloride solution was investigated using potential measurement, pH and gravimetric methods. The experiments were performed using zinc oxide as the inhibitor in 3.5% NaCl solution. From 200g of ZnO powder, and using distilled water, 25, 50, 75, and 100% zinc oxide inhibitor concentrations were prepared. A digital voltmeter was used to record potential measurements. A copper-copper sulphate electrode was used as the reference electrode. After the experiments, compressive strength of each block sample was determined. Weight loss values were obtained from the weight loss method and the inhibitor efficiency was calculated from the corrosion rate of each of the tested samples. The results were further analysed using the two-factor ANOVA test. Results showed varied concentrations of ZnO inhibitor and the test exposure time significantly affected the corrosion potential of the embedded steel rebar. The inhibitor gave appreciable corrosion inhibition performance of the embedded steel rebar at 100 and 75% concentrations with the weight loss of 600 and 800mg and corrosion rates of 0.000270 and 0.000357mm/yr respectively. An inhibitor efficiency of 41.02% was achieved at 100% ZnO concentration. ANOVA analysis confirmed the results at 95% confidence.
Nickel nanopowders were synthesized by a chemical reduction of nickel ions with hydrazine hydrate at pH 12.5. Sonication of the solutions created a temperature of 54-65°C to activate the reduction reaction of nickel nanoparticles. The solution pH affected the composition of the resulting nanoparticles. Nickel hydroxide nanoparticles were formed from an alkaline solution (pH10) of nickel-hydrazine complexed by dropwise titration. X-ray diffraction of the powder and the analysis of the resulting Williamson-Hall plots revealed that the particle size of the powders ranged from 12 to 14 nm. Addition of polyvinylpyrrolidone into the synthesis decreased the nickel nanoparticle size to approximately 7 nm. Dynamic light scattering and scanning electron microscopy confirmed that the particles were in the nanometer range. The structure of the synthesized nickel and nickel hydroxide nanoparticles was identified by X-ray diffraction and Fourier transform infrared spectroscopy.
Reinforcement corrosion is one of the biggest challenges faced by the construction industry, with billions of dollars spent on corrosion remediation and prevention. Recently, microbially induced calcium carbonate precipitation (MICCP) has been considered a novel method in corrosion mitigation of reinforced concrete (RC) structures. In the current investigation, fly ash (FA) based inoculum for construction industry was developed and tested for cell viability to define the shelf life of the carrier product. The results indicated that FA-based inoculum possessed a shelf life of 180 days with an effective cell count required to induce MICCP in reinforced concrete. FA-based inoculum was immobilized in fresh concrete supplemented with nutrients to study the corrosion mitigation potential. The prepared specimens were cured for 28 days and then subjected to impressed current-induced chloride corrosion. For corrosion assessment, well established electrochemical technique and a newly emerged electromechanical impedance (EMI) technique were employed separately on different RC specimens. In the electrochemical technique, open circuit potential (OCP), corrosion potential (Ecorr), corrosion current density (Icorr) were obtained over the test exposure; whereas in EMI technique, admittance signatures were acquired for the entire testing duration at an interval of 7 days. Further to examine the changes in admittance signatures, root mean square deviation (RMSD) was used to quantify the corrosion process. Results indicated that Icorr and RMSD were linearly increasing over the test exposure. The results clearly prove that the FA-based carrier material can be effectively used for the corrosion prevention and the emerging EMI technique can efficiently monitor the corrosion process.
In the present study, Schiff basestetrayltetrakis (azanylylidene) tetrakis ethan-1-yl-1-ylidene) tetraphenol (BTAT) and hydroxyimino (butan-2-ylidene amino)-biphenyl (4-yl imino) butan-2-one oxime (HABO) were prepared in the laboratory and utilized as corrosion inhibitor on mild steel (MS) in HCl solution by performinggravimetric and electrochemical studies.The offered corrosion inhibition efficiency of BTAT and HABO was 96.63% and 96.05% , respectively, in presence of 100 ppm inhibitor concentration at 298 K temperature. On the basis of gravimetric data and electrochemical analysis, it is inferred that adsorption of BTAT and HABO on MS surface occurs through mixed adsorption process and obeyed Langmuir adsorption isotherm.The surface analysisof uninhibited and inhibited sample was done by using FESEM, AFM, and XPS analyses to confirmthe adsorptionof inhibitor molecules on the MS surfacewhich caused the corrosion inhibition of mild steel. Density functional theory (DFT) and Monte Carlo simulations (MCS) was performed to support the results achieved from the gravimetric and electrochemical analysis.
Sn-Ni coatings (0 - 13 wt.% Ni) were electrodeposited on mild steel. The highest (Rp = 18561.1 Ω·cm²) and the lowest (Rp = 4756.7 Ω·cm²) corrosion resistance was observed for Sn-6 wt.% Ni and Sn-13 wt.% Ni coating, respectively. Higher corrosion resistance of Sn-6 wt.% Ni coating was due to low energy (100) surface texture, low energy CSL boundaries and formation of Ni3Sn4 phase at grain boundaries. Higher corrosion rate of Sn-13 wt.% Ni coating was due to highest fraction of high energy high angle grain boundaries, higher matrix strain and higher volume fraction of cathodic Ni3Sn4 phase.
This study investigated the chloride-induced depassivation and corrosion of mild steel in the magnesium potassium phosphate cement (MKPC) pore solutions at different magnesia-to-phosphate (M/P) ratios via several electrochemical methods and surface characterizations. Results showed that although the pH of MKPC is much lower than that of PC, the corrosion resistance of mild steel is significantly higher, with critical chloride values in MKPC being several orders higher than that in PC. Chloride-induced corrosion resistance increases with increasing M/P ratios. Whilst both pH and HPO4²⁻/PO4³⁻ ions influence the formation of corrosion products, the pH plays a dominant role in the corrosion resistance.
This work reports a novel ternary cement polymer composite coating (CPFNIC) consisting of fly ash, nanoparticles, and inhibitor with enhanced corrosion protection for steel rebars in a chloride environment. Electrochemical impedance spectroscopy (EIS) measurements, polarization curves, salt spray test, scanning electron microscopy (SEM), and Confocal Laser Scanning Microscopy (CLSM) were used to understand the corrosion protection mechanism and for characterization of corrosion products. The results show that the new coating significantly delayed the onset of corrosion on rebars in aggressive chloride environments due to the synergistic contributions from the additives used. The electrochemical studies (open circuit potential and corrosion current) indicate a significantly improved corrosion performance of CPFNIC as compared to uncoated rebars. The potentiodynamic polarization results of CPFNIC coated rebars showed high corrosion potential, low corrosion current density, three order higher polarization resistance, and two-order lower corrosion rate than the uncoated rebar. The EIS measurements showed a significantly higher charge transfer resistance for the CPFNIC as compared to the uncoated rebar. The visual inspection and weight loss measurements in salt spray and chemical resistance tests of CPFNIC coated rebars corroborated its improved resistance in chloride environment. Our results suggest the benefits of ternary composite cementitious coating on rebars in enhancing the corrosion protection.
In the present work, PCL/ZnO (polycaprolactone/ zinc oxide), PCL/NiO (polycarprolactone/nickel oxide), PCL/ CuO (polycarprolactone/copper oxide), and PCL/ZnO-NiO-CuO (polycarprolactone/ zinc oxide-nickel oxide-copper oxide) have been successfully fabricated and deposited on a mild steel through electrospinning technique. SEM, EDX, and FT-IR had been used to characterize all nanofiber coatings on the mild steel. A nanofiber layer of ZnO/NiO/CuO/PCL was utilized to coating the mild steel as a corrosion protector film in 1M HCl. A series of electrochemical techniques like Open circuit potential (OCP), Electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP) were used to analyse the anti-corrosion performance of the nanofiber layer ZnO/NiO/CuO/PCL. The results showed that both anodic and cathodic reactions sharp decline with shift in corrosion potential toward a positive direction in the Tafel plots. LPR results showed that the highest protection efficiency was 94.8% with ZnO-NiO-CuO/PCL nanofiber coating. EIS spectra showed that mild steel coated with ZnO/PCL, NiO/PCL, CuO/PCL, and ZnO-NiO-CuO/PCL, realization of capacitive conduct at high frequency and coating strength at law frequency part with resistor component 474.76 ohm.cm 2 , 527.35 ohm.cm 2 , 714.73 ohm.cm 2 , 744.80 ohm.cm 2 respectively, indicating the good barrier properties and high ohmic resistance of coatings. SEM displayed a straight, interconnected structure , relatively less porosity with uniform fibers diameter. The fibers had average diameter 429 nm, 525 nm, 639 nm, and 443 nm for ZnO/PCL, NiO/PCL, CuO/PCL, and ZnO-NiO-CuO/PCL respectively. EDX and FT-IR results confirmed the existence of ZnO, NiO, and CuO and approved the distribution into PCL matrix.. Results of the present study confirmed that ZnO-NiO-CuO/PCL electrospinning nanfiber coating could be considered as a new metallic oxide nanocomposite coating for a mild steel with excellent corrosion resistance.
Nickel-iron alloy is broadly utilized in the industrial field due to its fabulous mechanical properties. How to prepare nickel-iron alloy with better corrosion resistance more efficiently is an important concern. Based on this, the WC particles enhanced nickel-iron coatings were fabricated by jet electrodeposition (JED) at a high current density of 100A/dm². It was found that increasing the deposition temperature appropriately during JED is beneficial to obtain Ni-Fe-WC coating with the higher number of hard particles. Specifically, the maximum WC particles proportion reaches 4.47 wt% at 55°C. The electrochemical corrosion behavior of coating was measured by polarization curve and electrochemical impedance spectroscopy (EIS). The polarization curve test results displayed that the Ecorr positively shifted from -0.402 to -0.281 V and the icorr reduced from 25.13 to 7.05 μA/cm² with the increase of WC particles proportion. Meanwhile, the EIS test results exhibited that the impedance of coating enhanced from 12720 to 59140 Ω·cm². The neutral salt spray test (NSS) was used to simulate the corrosion of coating in a seawater environment. The NSS results showed that with the increase of WC particles, the corrosion products decreased gradually and the degree of corrosion decreased. The analysis showed that WC particles can help the grain growth and release the internal stress in the coating. Larger grain sizes reduces intergranular corrosion and smaller internal stress help to alleviate stress corrosion cracking. The above research can provide theoretical support for the efficient preparation of particle enhanced composite coating with strong corrosion resistance.
In the present study, hydroxyapatite/ZnO nanocomposite coatings were developed on NiTi superelastic alloy via pulse electrodeposition technique under three different current densities. The morphological observations (FESEM) indicated that under 6 mA/cm2, a compact, uniform composite layer could form, whereas lower or higher current densities resulted in non-uniform, porous coatings with uneven distribution of nanoparticles. XRD and FTIR studies revealed that pure hydroxyapatite was not achieved below 6 mA/cm2. Topographic features (AFM) were assessed and demonstrated a continuous rise in roughness parameters as current density increased. The corrosion behavior was investigated through potentiodynamic polarization as well as impedance spectroscopy techniques. According to the extracted data, the porosity and non-uniformity of coatings formed under 3 and 9 mA/cm2 caused a detrimental effect on the corrosion resistance of surfaces. The layer obtained under 6 mA/cm2 showed resistance (Rc) which was almost two times greater than those deposited under 3 and 9 mA/cm2 current densities. Last but not least, the bioactivity of coatings was evaluated in simulated body fluid. It was observed that more compact deposits offered more active sites for apatite nucleation, resulting in refined cauliflower-like grains. Accordingly, it can be asserted that the best composite coating was achieved under 6 mA/cm2 current density.
Metal-organo-ceramic nanocomposite coatings were prepared via electrodeposition as corrosion protection coatings. A diazonium synthesis procedure was used to successfully graft ferrocene onto CeO2 nanoparticles. The modified nanoparticles were characterized by fourier-transform infrared spectroscopy (FTIR), solid-state NMR, electrochemical techniques, atomic absorption spectroscopy (AAS), and thermogravimetric analysis (TGA). A mixture of the grafted nanoparticles and nickel ions was added to an electrolyte plating solution for deposition of a Ni Fc-CeO2 nanocomposite coating onto steel substrate as a corrosion protection layer. The effect of CeO2 and ferrocene-CeO2 nanoparticles on the formation, morphology, composition, and corrosion resistance of the nickel coating was investigated by potentiodynamic polarization, powder x-ray diffraction (XRD), scanning electrochemical microscopy (SEM), inductively coupled plasma mass spectrometry (ICP-MS), and electrochemical impedance spectroscopy (EIS).
Sugarcane bagasse ash sand (SBAS) can be used as a bioadditive in concrete. However, little is known about its effects on the steel corrosion process. This paper reports the evaluation of the corrosion susceptibilities of steel immersed in simulate concrete pore solutions, with addition of SBAS, to understand the corrosion process in reinforced structure. The open-circuit potential profiles and polarisation curves suggested the favourable formation of a passive film on the steel immersed in the SBAS-containing medium. Electrochemical impedance spectroscopy confirmed that the SBAS-containing medium presents better passivating properties, showing that this recycled material can be used as corrosion inhibitor for reinforced concrete, encouraging its use in the civil industry.
Incorporation of zinc oxide (ZnO) nanoparticles and ZnO based nanocontainers with corrosion inhibitor Safranin into the matrix of standard zinc coatings is applied for preparation of coatings with improved corrosion protection for mild steel. A cationic polyelectrolyte polyethylenimine (PEI) is used to stabilize the ZnO suspension before electrodeposition of the ZnO nanoparticles on the steel surface. Encapsulation of Safranin is realized in polymer coatings on ZnO nanoparticles prepared using layer-by-layer assembly of polyacrylic acid (PAA) and PEI. The average size and surface charge of the PEI coated ZnO nanoparticles and ZnO based nanocontainers with inhibitor are identified using dynamic and electric light scattering methods and microelectrophoresis. The ZnO nanoparticles or ZnO nanocontainers are electrodeposited on steel (cathode) substrates at pH 7.5 to minimize the effect of ZnO dissolution. In a second step, ordinary zinc coatings are electrodeposited on the ZnO nanoparticles or ZnO nanocontainers covered steel samples from zinc sulfate electrolyte at pH 4.5-5.0. The surface morphology of the coatings and their corrosion behavior are studied by scanning electron microscopy and electrochemical methods potentiodynamic polarization and polarization resistance. The results show better corrosion protection of steel by composite coatings as compare to the bare zinc coating. The composite coating with inhibitor shows better protective characteristics in comparison with the other one. The two-step approach described herein can be used for preparation of composite coatings where preservation of particles functionality is required.
Marine structures come into contact with the seawater. Corrosion occurs on the walls of these structures and can quickly lead from surface damage to aesthetics impairment. The main cause of the corrosiveness are chloride ions which facilitate initiation and propagation of pits. Stainless steels provide a wide range of applications in seawater environments. They are used for the construction of heat exchangers, tanks and capacitors for electrical systems, refrigeration systems for power plants, tidal power, wind turbines localized at sea. Mild steel find its role in almost every product created from metal due to its low cost and easy availability. The polymeric materials are having multiple adsorption sites for bonding with metal surface and provides higher inhibition efficiency than the corresponding monomers. In the present work, the corrosion inhibition of mild steel in 3.5% NaCl by PVDF/ ZrO2 composites were studied. The composite samples were characterized by using XRD, FTIR and SEM. Potentiodynamic polarization and electrochemical impedance spectroscopic techniques were used to explore the enhanced corrosion inhibition of composites. The corrosion inhibition efficiency of PVDZr composites were found to increase with increase in concentration of ZrO2.
The anti-corrosion potency of three synthesized 8-hydroxyquinoline derivatives, namely 5-(azidomethyl)-7-(morpholinomethyl)quinolin-8-ol (HM1), 2-(8-hydroxy-7-(morpholinomethyl)quinolin-5-yl)acetonitrile (HM2), 5-(azidomethyl)-7-(piperidin-1-ylmethyl)quinolin-8-ol (HM3) in hydrochloric acid for mild steel was investigated using
weight loss and electrochemical techniques. Potentiodynamic polarization (PDP) data reveal that all three compounds were cathodic inhibitors, with HM3 presentation significant mixed-type effect at high inhibitor concentrations (10-3 M). Electrochemical impedance spectroscopy (EIS) data reveal better adsorption of compounds species on MS surface at increased inhibitor concentrations with HM1, HM2 and HM3 reaching a maximum efficiency of 90, 89 and 88%. The three compounds HM1, HM2 and HM3 were inclined towards the Langmuir adsorption-isotherm by spontaneous chemical-physical adsorptions of inhibitors on the mild steel surface. The correlation between the electronic properties and inhibition efficacies of the tilted inhibitors was determined by using simple linear regression technique. Electronic properties were calculated for neutral and protonated forms in a polarizable continuum model using the DFT method at the B3LYP/6-311+G (d, p) level of theory. The active adsorbed sites of HM1-HM3 on the metal surface were determined by analyzing their corresponding electrostatic surface potentials (ESP). Furthermore, molecular dynamics simulations have been performed to illustrate the most conceivable adsorption configuration between the inhibitors and metal surface.
An efficient accelerated corrosion test method is the foundation for experimental investigation of corrosion behaviors of reinforcing steel embedded in mortar and concrete. In this work, the electrochemical mechanisms of four typical electrolytic accelerated corrosion methods (EACMs) currently adopted by numerous researchers are analyzed and compared, including embedded auxiliary electrode method, soaking method, part soaking method, and surface coating method. Based on the electrochemical mechanism, a numerical model for predicting the distribution of rust layers around steel rebar under EACMs is established. The parameters influencing the electrolytic accelerated corrosion (e.g. position of electrodes for embedded auxiliary electrode method, the electrolyte solution level for other methods) are investigated. It is concluded that the distribution profiles of rust layer vary with the EACMs adopted; by controlling and optimizing the critical parameters of EACMs, non-uniform distribution pattern of rust around rebar that is similar to that by natural corrosion can be induced in a short time.
Parts of reinforcing steel bar (rebar) used in concrete are subjected to high levels of plastic strain due to various operations during construction. This work presents the corrosion behavior of pre-strained rebars in simulated concrete pore solution, both in the presence and in the absence of chlorides. Results obtained from the electrochemical tests (EIS and cyclic polarization) in chloride-free pore solutions have indicated the formation of more protective passive films in the strained steels. However, when contaminated with chlorides, the strained steels have exhibited higher corrosion susceptibility due to the changes in the surface condition, microstructure and dislocation density.
The present study attempts to obtain the critical strains in concrete induced on account of reinforcement corrosion by simulating the expansive pressure of corrosion products using grout. Surface strains induced in hollow concrete cylinders due to expansion of grout filled inside the hollow portion were continuously monitored to experimentally validate the well-known thick-walled uniform cylinder model used in reinforcement corrosion problems. The study shows that expansive grout could effectively simulate the internal pressure generated in accelerated corrosion tests, and can be used as a means of obtaining critical strains in relatively shorter duration in laboratory studies.
A Ni/ZnO system was prepared by coprecipitation and characterized after reduction at different temperatures (350, 400, 450 and 500 oC) using TG-MS, H2-TPR, N2 physisorption, XRD, SEM, H2 and CO chemisorption, TEM, EPR and XPS. H2 and CO chemisorption experiments combining with XRD, SEM and TEM analysis showed evidence for strong metal-support interactions (SMSI) between Ni and ZnO particles, and the degree of SMSI strengthened as the reduction temperature rose. TEM, EPR and XPS studies revealed that the generation of SMSI was attributed to the geometric decoration of Ni particles by ZnO, electron transfer from ZnO to Ni atoms as well as the the chemical interaction between Ni and ZnO leading to the formation of NiZn alloy. Methanation of CO was used as probe reaction to characterize the effect of SMSI on the catalytic performance of Ni/ZnO. The results showed that SMSI in general had a remarkable suppression effect on the methanation actvity, but light degee SMSI state facilitated enhancing the selectivity and stability of CO methanation, interestingly, the suppressed activity can also be restored with different degree via re-oxidization and re-reduction treatments under mild conditions. The discovery of SMSI between Ni and ZnO gives a new understanding of the interaction between Ni and support, and provides a way to tune the interaction between Ni and support as well as a way to regulate the methanation performance of Ni/ZnO catalyst, or Ni-based catalysts.
A one-step electrospinning technique was used to prepare a protective superhydrophobic PVDF-ZnO nanocomposite coating for aluminum against corrosion. The wettability and morphology of the prepared coating surfaces was characterized using water contact angle and contact angle hysteresis measurements, scanning electron microscopy, fourier transform infrared spectroscopy and atomic force microscopy. In addition, the corrosion resistance for Al with PVDF polymer and the PVDF-ZnO nanocomposite coatings compared to the bare Al was investigated by electrochemical impedance spectroscopy and Tafel polarization techniques. The results showed that, the water contact angle and the contact angle hysteresis of the prepared PVDF-ZnO nanocomposite coating were 155 ± 2 and 4.5 ± 2 °, respectively. In addition, compared to the sprayed PVDF-ZnO coating, the concentration of ZnO nanoparticles in the electrospun coating was only one sixth to obtain the same water contact angle, better distribution of ZnO nanoparticles was achieved without using any dispersing agent. The analysis of the corrosion results revealed that, the superhydrophobic PVDF-ZnO coating showed a corrosion protection efficiency for Al that is much higher than that of the PVDF one.
The corrosion performance of TiO2 doped polypyrrole coated (PPy-TiO2) aluminum and application as anode material for direct methanol fuel cell were investigated. The surface morphology was analyzed by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction technique. The conductivity values of coatings were measured with four probe technique. The electrochemical impedance spectroscopy and anodic polarization obtained at periodic intervals for 168h. The corrosion resistance of Al/PPy-TiO2 is almost 5 times higher than Al for 168h immersion. PPy-TiO2 coating has better electrocatalytic activity than PPy for methanol oxidation reaction.
A robust wear/corrosion-resistant superhydrophobic polyvinylidene fluoride (PVDF)/fluorinated ethylene propylene (FEP)/carbon nanofibers (CNFs) composite coating with a water contact angle (WCA) of 164°±1.5° and a slide angle of 5° has been fabricated through the combination of chemical etching and spraying technique. The WCA of the coating still maintains 141°±1.2° after 10000 times rubbing due to the designed internal nano/micro-structure and the slide angle increases from 5°±0.2° to 20°±0.5°. The prepared coating also demonstrates excellent corrosion-resistance property under strongly acidic or alkaline conditions for 15 days. The wear-resistance of the superhydrophobic coating is approximately 5 times higher than the pure PVDF coating and commercial fluorocarbon coating. These excellent mechanical properties are attributed to the new groups of C = C and C-C by dehydrofluorination of PVDF and the new β-phase of PVDF by recrystallization of the α-phase. Furthermore, the enhanced adhesive ability of the coating corresponds with Grade 1 according to GB/T9286, mainly because that the interaction force among PVDF macromolecules can be intensified by chemical cross-linking and the hydroxyl groups formed on the surface of the aluminum plate by etching. It is believed that this robust multifunctional superhydrophobic coating may have the potential values in large-scale application.
Organic coating approaches for corrosion protection with inherently conducting polymers have become important because of restriction on the use of heavy metals and chromates in coatings due to their environmental problems. The present work is directed towards the synthesis of polyaniline (PANI) and polyaniline–SiO2 composites (PSCs) by chemical oxidation polymerization in the presence of phosphoric acid and evaluation of synthesized PANI and PSCs for protection of mild steel from corrosion in a strong aggressive medium (i.e. 1.0 mol L–1 HCl). A suitable coating with PSC was formed on mild steel using epoxy resin by the powder coating technique. A comparative study of the corrosion protection efficiency of mild steel coated with PANI and PSC in 1.0 mol L–1 HCl solution was evaluated using the Tafel extrapolation, chrono-amperometry and weight loss methods. The PSC coating showed that a significant reduction in the corrosion current density reflects the better protection of mild steel in an acidic environment. Higher protection efficiency up to 99% was achieved by using PSC-coated mild steel at 6.0 wt% loading of PSC in epoxy resin. The coating performance and corrosion rate of mild steel were investigated by using immersion of polymer-coated mild steel in 1.0 mol L–1 HCl for 60 days and indicated that PSC-coated mild steel showed better performance from corrosion than PANI in an acidic medium.© 2012 Society of Chemical Industry
The Zn and Zn–ZrO2 composite coatings were produced by electrodeposition technique using sulphate bath. ZrO2 particles were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The ZrO2 particle size distribution in the plating bath and Zeta potential and the ZrO2 were measured using dynamic light scattering technique (DLS). The corrosion resistance properties of Zn and Zn–ZrO2 composite coatings were compared by examining the experimental data acquired through polarization, open circuit potential (OCP) and Tafel measurements. The corrosion environment was 3.5wt% NaCl solution. The variation of amount of ZrO2 in the solution on their % wt inclusion in the composite and on composite microhardness was investigated. XRD patterns were recorded for Zn and Zn–ZrO2 coatings to compare their grain size. The SEM images of coatings before and after corrosion under chemical and electrochemical conditions were presented. The results were analyzed to establish the superiority of Zn–ZrO2 composite over Zn coating.
Polyaniline/nano-CeO2 composite microspheres with an average diameter of 7μm have been synthesized in a toluene/water emulsion solely stabilized by CeO2 nanoparticles (Pickering emulsion). Various experimental techniques were employed to characterize the polyaniline/nano-CeO2 composite microspheres. The microspheres are flaky polyaniline/nano-CeO2 composite particles; in the microspheres, polyaniline was amorphous while the CeO2 nanoparticles maintained their cubic crystal structure; CeO2 nanoparticles were partly enwrapped by polyaniline. A mechanism for the formation of the polyaniline/nano-CeO2 composite microspheres was proposed.
Coatings prepared from polyaniline–nano-TiO2 particles synthesized by in situ polymerization were found to exhibit excellent corrosion resistance much superior to polyaniline (PANI) in aggressive environments. The corrosion studies were carried out on steel plates coated with these formulations containing 10wt% polyaniline prepared with different concentrations of nano-TiO2. The electrochemical impedance spectroscopy was studied at periodic intervals during exposure to hot saline (65°C) conditions for prolonged durations over a period of 90h. The open circuit potential (OCP) was found to shift with time from −0.38V SCE to more anodic side (−0.2V SCE) much above that of bare steel (−0.5V SCE). The presence of nano-TiO2 was found to be vital in the prevention of corrosion and the shift of OCP to anodic side. From these data, one could envisage more than 100 times improvement in the corrosion resistance especially for polyaniline prepared with 4.18wt% nano-TiO2. The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nano-size TiO2, redox properties of polyaniline as well as very large surface area available for the liberation of dopant due to nano-size additive.
Impact of agro-industrial waste on steel corrosion susceptibility in media simulating concrete pore solutions
- M F Gromboni
- A M De Salesam Rezende
- J P Moretti
- P G Corradini
- L H Mascaro
- MF Gromboni
Validation as construction design method of the anti-corrosion process for marine steel structures using COMSOL Multiphysics® through mock-up sheet piles
- T Iwamoto
Crosslinked PVDF-membranes for solvent resistant nanofiltration
- M Mertens
- C Van Goethem
- M Thijs
- G Koeckelberghs
- I F Vankelecom