Electrochemical Corrosion Measurements Research Articles

Green and Heavy-Duty Anticorrosion Coatings: Waterborne Epoxy Thermoset Composites Modified through Variation of Zinc Dust Loading and Incorporation of Amine-Capped Aniline Trimer and Graphene Oxide.

In this study, an array of environmentally friendly and heavy-duty anticorrosion composite coatings were prepared. The synthesis involved amine-capped aniline trimer (ACAT) produced by an oxidative coupling reaction and graphene oxide (GO) prepared based on Hummer's method, and later, the waterborne epoxy thermoset composite (WETC) coatings were prepared by thermal ring-opening polymerization of EP 147w, a commercial waterborne epoxy resin, in the presence of ACAT and/or GO with zinc dust (ZD). A synergistic effect was observed by replacing a significant amount of the ZD loading in the WETC by simultaneously incorporating a small amount of ACAT and GO. The electrochemical corrosion measurements of the as-prepared WETC coatings indicated that incorporating 5% w/w ACAT or 0.5% w/w GO separately replaced approximately 30% w/w or 15% w/w of the ZD, respectively. Moreover, the WETC coatings containing 5% w/w ACAT and 0.5% w/w GO simultaneously were found to replace 45% w/w of the ZD. A salt spray test based on ASTM B-117 also showed a consistent trend with the electrochemical results. Incorporating small amounts of ACAT and GO in WETC coatings instead of ZD not only maintains the anticorrosion performance but also enhances adhesion and abrasion resistance, as demonstrated by the adhesion and abrasion tests.

Effects of preheating on laser beam–welded NSSC 2120 lean duplex steel

AbstractDuplex stainless steels show sustainable alternative for the conventional austenitic grades, with higher strength, higher resistance against stress corrosion cracking, and lower purchase cost. Thus, duplex stainless steel gains more attention in construction, oil and gas, and chemical industries. Among duplex stainless steels, low nickel and low molybdenum alloyed lean duplex stainless steel are a cost-effective substitution of austenitic grades. However, keeping the balanced ferrite/austenite phase ratio in the weld metal can be challenging, mostly for autogenous and low heat input welding processes. In our research, a newly developed NSSC 2120 lean duplex stainless steel grade was welded autogenously by fiber laser welding process. Different welding parameters and preheating temperatures were used during the experiments. The welds were evaluated by microscopic and metallographic techniques, and also by electrochemical corrosion measurements. The welding parameters and the preheating temperature greatly influenced the weld shape and the austenite content in the weld metal. It was found that the focus point distance from the sheet surface had significant effect on the weld geometry. Changing the focus point distance to + 2 mm, the penetration depth increased from 4.96 to 5.53 mm, and increased the austenite content by 2.6%. Due to the preheating the welds became wider and shallower, e.g., from 4.96 to 4.08 mm penetration depth, while the cross-section are increased from 5.10 to 6.12 mm2 at the same sample. The preheating resulted in more intergranular austenite formation, which meant maximum 4% increase in the weld metal. The increasing austenite content resulted in increasing pitting corrosion resistance in 3.5% NaCl electrolyte, the highest increase was 90 mV.

Impact of Desulfovibrio ferrophilus IS5 biocorrosion time on X80 carbon steel mechanical property degradation

Three different incubation times (7, 14 and 21 d) were used to immerse X80 carbon steel dogbone coupons in deoxygenated enriched artificial seawater at 28 °C inoculated with Desulfovibrio ferrophilus (strain IS5), a very corrosive sulfate reducing bacterium to cause microbiologically influenced corrosion (MIC). It was found that 21 d immersion had the largest weight loss (24.8 mg cm−2 equivalent to 0.55 mm/year corrosion rate), smallest sessile cell count (6.8 × 108 cell/cm2), deepest pit depth (30.6 μm), and most severe mechanical degradation (9 % loss in ultimate strength and 18 % loss in ultimate strain). Due to nutrient depletion in the static incubation system, corrosion rate and sessile cell count were the highest at 0.82 mm/year and 1.1 × 109 cell cm−2, respectively at 7 d. The results from scanning electron microscopy, X-ray photoelectron spectroscopy and confocal laser scanning microscopy analyses and electrochemical corrosion measurements supported the sessile cell counts and biocorrosion weight loss data.

Heat-Affected Zone Characterization of X2CrNiN22-2 Lean Duplex Stainless Steel by Metallographic and Electrochemical Techniques

This research aimed to investigate the heat-affected zone of lean duplex stainless steel grade X2CrNiN22-2. Different heat-affected zone microstructures and grain morphologies were developed by Gleeble simulations. The governing microstructures were evaluated by metallographic techniques and electrochemical corrosion measurements. It was found that the 1200-800 °C cooling time significantly affects the microstructure, austenite content, and corrosion properties. The average austenite content in the case of 1 s cooling time is 30.7 ± 1%, which increased with the longer cooling times up to 38.6 ± 0.9%. The rapid cooling times resulted in a more ferritic microstructure, which promoted nitride precipitation in the ferrite grains. The nitride precipitations acted as nucleation sites for pitting initiation in 3.5 wt.% NaCl solution. The lowest pitting potential was measured in the case of the most rapidly cooled sample: 573 ± 31 mV, while the balanced, annealed microstructure had much better pitting corrosion resistance, showing a pitting potential of 1308 ± 62 mV vs. the Ag/AgCl (KCl sat.) reference electrode. The results of this research can be used in designing welding parameters for the welding of the X2CrNiN22-2 lean duplex stainless steel.Graphical

Preparation, microstructure and corrosion resistance of Al2O3 coatings by cathodic plasma electrolytic deposition on sintered NdFeB permanent magnet

The Al2O3 ceramic coatings were prepared on the sintered NdFeB magnets by cathodic plasma electrolytic deposition (CPED) method in aluminum nitrate alcohol solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermal shock, hydrothermal weight loss, electrochemical corrosion and physical property measurement system (PPMS), respectively. The results show that the coatings mainly consist of γ-Al2O3 and α-Al2O3 phases, and the volume of α-Al2O3 increases with increasing the voltages. The surface of the coatings shows a typical coral reef structure, and the thickness of the coatings increases from 29 µm to 53 µm with increasing the voltages. The Al2O3 coatings have excellent thermal shock resistance as well as the excellent corrosion resistance in hydrothermal conditions. The corrosion resistance of the coatings enhances with increasing the voltages, reaching the strongest at 470 V, and then decreases. This study provides a new method for forming ceramic coatings on the surface of sintered NdFeB magnets to improve its corrosion resistance.

Stress corrosion cracking failure of X80 carbon steel U-bend caused by Desulfovibrio vulgaris biocorrosion

Sulfate reducing bacteria (SRB) are widely present in oil and gas industry, causing pitting corrosion on pipeline steel. Stress corrosion cracking (SCC) often occurs in the presence of mechanical stress before pitting perforation failure, leading to economic losses and even catastrophic accidents. In this study, stress distribution simulation using the finite element method (FEM), corrosion analysis techniques and electrochemical corrosion measurements were employed to investigate the SCC mechanism of X80 pipeline steel caused by Desulfovibrio vulgaris, which is a common SRB strain used in microbiologically influenced corrosion (MIC) studies. It was found that D. vulgaris MIC caused sharp microcracks on an X80 U-bend coupon after only 2 weeks of immersion at 37 °C in the deoxygenated ATCC 1249 culture medium inoculated with D. vulgaris. The X80 U-bend coupon's weight loss-based uniform corrosion rate for the 12 cm2 surface was 60% of that for the unstressed flat square coupon (2.3 mg cm−2 vs. 3.8 mg cm−2). This was likely because the square coupon had wide MIC pits, providing a larger effective surface area for more sessile cells (4.2×108 cells cm−2 on square coupon vs. 2.4×108 cells cm−2 on U-bend coupon) to attach and harvest more electrons. An SCC failure occurred on an X80 U-bend pre-cracked at the outer bottom after a 6-week immersion in the D. vulgaris broth. Apart from MIC damage, this could also be because D. vulgaris metabolism increased the availability hydrogen atoms on the steel surface, and promoted the diffusion of hydrogen atoms into the metal lattice, thus increasing the brittleness of the steel.

Mitigation of galvanized steel biocorrosion by Pseudomonas aeruginosa biofilm using a biocide enhanced by trehalase

Pseudomonas aeruginosa is a facultative bacterium that is pathogenic. It is ubiquitous in the environment including air handling systems. It causes microbiologically influenced corrosion (MIC) aerobically and anaerobically. In this work, P. aeruginosa was grown as a nitrate reducing bacterium (NRB) in Luria-Bertani medium with KNO3 at 37 °C. Trehalase, an enzyme which plays a crucial role in biofilm formation was found to enhance the treatment of P. aeruginosa biofilm and its MIC against galvanized steel by tetrakis-hydroxymethyl phosphonium sulfate (THPS) green biocide. After a 7-d incubation, 30 ppm (w/w) trehalase reduced sessile cell count by 0.8-log, and it also reduced galvanized steel weight loss by 14%, compared to 2.3-log and 39%, respectively for the 30 ppm THPS treatment. The combination of 30 ppm THPS + 30 ppm trehalase reduced sessile cell count further by 0.1-log and weight loss by 13% compared to using THPS alone. Electrochemical corrosion measurements supported weight loss results. The injection of 20 ppm riboflavin into a 3-d P. aeruginosa broth failed to accelerate the corrosion rate, suggesting that nitrate reducing P. aeruginosa MIC of galvanized steel did not belong to extracellular electron transfer-MIC, because Zn was hydrolyzed after the microbe damaged the passive film.

Wear, corrosion and oxidation characteristics of consolidated and laser remelted high entropy alloys manufactured via powder metallurgy

High entropy alloys have promising wear, oxidation, and corrosion properties compared to conventional alloys and superalloys. In the present study, CrCuFeNiAl0.5 and CrCuFeNiAl0.5Si0.5 alloys were prepared using a traditional powder metallurgy process and then remelted the surfaces via laser. The laser remelting (LR) process gains a denser and more homogeneous surface to alloys. Pressureless consolidated and laser-remelted specimens were subjected to wear, corrosion, and oxidation tests. In the wear tests, it was observed that the wear resistance of Si-containing samples was better due to higher hardness. However, the laser remelting process has mostly increased rather than reduced wear losses. The less volume loss of laser-melted samples was attributed to the almost pure Cu in its content. There is little difference among all samples in electrochemical corrosion measurements. The formation of a fragile passivation layer was observed in potentiodynamic polarization curves of CrCuFeNiAl0.5Si0.5 and LR-CrCuFeNiAl0.5Si0.5 alloys. The alloy with the best corrosion resistance is CrCuFeNiAl0.5Si0.5, whose icorr value is 0.936 × 10−6 A/cm2. After high-temperature oxidation tests, the CrCuFeNiAl0.5 alloy exhibited the worst oxidation performance due to not forming a protective oxide layer on the surface, while LR enabled the protective oxide scale in a short oxidation time. The presence of Si in this alloy relatively enhances the oxidation resistance. The best oxidation performance was observed in LR-CrCuFeNiAl0.5Si0.5 due to the forming of a protective Al2O3 layer during the oxidation tests.

Cysteine as an Alternative Eco-Friendly Corrosion Inhibitor for Absorption-Based Carbon Capture Plants.

Inorganic corrosion inhibitors are commonly applied to mitigate severe corrosion in absorption-based carbon capture plants. They are, however, not environmentally friendly, posing a health risk, harming the environment, and making chemical handling and disposal costly. Therefore, this study evaluated the corrosion inhibition performance of an amino acid, namely cysteine, with the aim of providing an eco-friendly alternative to the commercial inorganic corrosion inhibitors. Electrochemical and weight loss corrosion measurements showed that cysteine was effective in protecting carbon steel at all process operating conditions. At 80 °C, a 500 ppm cysteine could provide up to 83% and 99% inhibition efficiency under static and dynamic flow conditions, respectively. Its inhibition efficiency could be improved when the cysteine concentration, solution temperature, and flow condition were altered. Cysteine was an anodic corrosion inhibitor and underwent spontaneous, endothermic, and combined physical and chemical adsorption that followed the Langmuir adsorption isotherm model. The quantum chemical analysis indicated that cysteine had a high reactivity with metal surfaces due to its low energy gap and high dipole moment. The EDX analysis revealed a significant sulphur content on the metal substrate, indicating that cysteine's mercapto group played an integral role in forming an effective adsorption layer on the metal interface.

Synergistic Effect of Electrocatalytic Characteristics of a Redox Segment and Gas Barrier of rGO to Significantly Replace the Loading of Zinc Dust in Solvent-Based Epoxy Composites Applied for Heavy-Duty Anticorrosion Coatings

Zinc-rich epoxy coating plays a major role in current heavy-duty corrosion protection solutions, yet high loading of zinc dust (ZD) weakens the coating flexibility and adhesion capability of the overall coating. This work demonstrated the successful incorporation of small amounts of rGO and aniline pentamer (AP)-based diamine into zinc-rich non-electroactive epoxy thermoset (NEET) as a novel heavy-duty anticorrosion coating composite. This coating composite promoted its wear resistance without sacrificing anticorrosion performance and adhesion ability while effectively reducing the loading of ZD. Based on a series of electrochemical measurements, an electroactive epoxy thermoset (EET) containing 5 wt % electroactive AP-based diamine (DAAP) and 0.5 wt % rGO can replace 70 wt % ZD and shows equivalent anticorrosion performance under an accelerated salt-spray assay and electrochemical corrosion measurements. Furthermore, coatings containing DAAP and rGO exhibited improved wear resistance and good adhesion capability.

Influence of the powder feed rate on the properties of HVOF sprayed WC-based cermet coatings

In this study, the characteristics of HVOF sprayed WC/Co-Cr and WC/Cr3C2/Ni coatings were investigated in correlation with the variation of the powder feed rate. For this purpose, the mass flow was adjusted to four different levels. The other process parameters were all kept constant. The morphological and mechanical properties as well as the electrochemical corrosion behaviour were investigated and associated with the achieved microstructure.Both scanning electron microscopy and confocal laser scanning microscopical images of the cross sections demonstrated a good correlation between the selected powder feed rate and the degree of internal porosity produced, which can be attributed to the deposition process. The coatings which fulfilled the requirements of the pre-qualification step were selected for further hardness measurements, tribological tests and electrochemical corrosion measurements in a 3.5 wt% NaCl aqueous solution.It was found that the powder feed rate strongly influenced the characteristics of the HVOF-sprayed cermet coatings. The tendency to crack formation, especially at the interface coating/substrate, was lower for the samples coated with a lower mass flow rate. These studies have shown that the applied powder feed rates had an important influence on the coatings microstructure and implicitly on the sliding wear behavior respectively on the electrochemical corrosion resistance of the investigated cermet coatings.

PEO/Polymer hybrid coatings on magnesium alloy to improve biodegradation and biocompatibility properties

There is an increasing tendency towards replacing permanent implants with biodegradable magnesium implants in temporary bone applications like screws and pins. This inclination arises from the close mechanical properties and biocompatibility of magnesium (Mg) to bone. Nonetheless, the high degradation rate of Mg can be a reason for implant loosening even in the early weeks after implantation. This study aims to design a multifunctional multilayered coating based on a combination of inorganic and organic layers for controlling the degradation behaviour. An inorganic layer was created on the substrate of magnesium alloy, AZ31B Mg, via plasma electrolytic oxidation (PEO) process while an organic layer of elastic poly trimethylene carbonate (PTMC) polymer was deposited by dip coating in the vacuum condition to have open pores of the PEO layer sealed. Subsequently, the coating was functionalized with a biomimetic polydopamine layer. The electrochemical corrosion measurements in simulated body fluid (SBF) showed the resistance against corrosion increases after deposition of the polydopamine functionalized PTMC on the PEO layer. In-vitro investigations in SBF evaluated the bioactivity of the multilayered coating. Moreover, MTT assays did not show cytotoxicity in the coating. Cell culture evaluations helped to determine the cell spreading and adhesion on the multilayered coating. Based on our findings, the fabricated layered composite on the biodegradable AZ31B alloy would add privileges to the sector of temporary implants.

Beads‐milling of waste Si sawdust into micro‐flakes and applied in UV‐curable polystyrene composites for anticorrosion coatings

AbstractIn this study, the waste Si sawdust (WSS) obtained from the silicon wafer sawing process was applied in polymer composite for anticorrosion application for the first time. The WSS powder was processed through a beads‐milling (BM) procedure using Zr beads. Subsequently, WSS‐based polystyrene (PS) composite coatings were prepared by photo‐polymerization of styrene monomers in the presence of a specific amount of WSS powder with UV radiation. The as‐prepared WSS‐based PS composite coatings were subsequently investigated and characterized by a series of tests. Anticorrosion performance of sample‐coated cold‐rolled steel (CRS) electrodes were investigated by a series of electrochemical corrosion measurements (e.g., Tafel, Nyquist, and Bode plots) in saline conditions. Gas permeability analysis (GPA) study of these membranes were also determined to support the anticorrosion data of coatings. It should be noted that the WSS‐based PS composite coatings were all found to exhibit better corrosion resistance than that of neat PS. Moreover, the composite coating with higher loading of WSS was found to show better anticorrosion performance than of lower loading of WSS. This may be attributed to the dispersion of WSS particles in PS can effectively prolong the diffusion path of corrosive factors, as evidenced by the corresponding GPA results.

Electrophoretic deposition of alginate/bioglass composite coating on Mg[sbnd]Ca alloy for degradable metallic implant applications

Surface modifications using bioactive coatings can be utilized effectively to tailor the rate of degradation and enhance biomineralization of magnesium (Mg) alloys. This study examines the effect of alginate/bioglass composite (Alg/BG) coating developed by electrophoretic deposition (EPD) on the biodegradation, bioactivity and biocompatibility of MgCa alloy. Electrochemical corrosion measurement in NaCl solution and in vitro degradation test conducted using simulated body fluid (SBF) revealed that the coated sample has better degradation resistance and bioactivity than bare MgCa alloy. It was noted that the hydrophilic Alg/BG coating enhances biomineralization and promotes in situ deposition of hydroxyapatite on the sample surfaces. The cell culture studies conducted using L929 cells revealed that the coated samples could promote cell adhesion as well as proliferation. Thus, electrophoretic deposition of Alg/BG is suggested as a suitable coating strategy to promote biomineralization and tailor the biodegradation of the MgCa alloy in the physiological environment.

Bi-functional inhibitors of zinc corrosion and dendrite formation in aqueous electrolyte: Insights from experiments and theoretical calculations

An organic compound 1-butyl-3-methylimidazolium phosphate dibutyl ester salt (BD) is studied for the first time to effectively inhibit zinc corrosion and the formation of zinc dendrites. Through SEM, AFM, XPS, FTIR, XRD, theoretical calculation, and electrochemical corrosion measurements, the inhibition mechanism of BD on zinc is investigated in 2 M ZnSO4. The maximum anti-corrosion efficiency is over 91% in 2.5 mM BD. Besides, BD can also inhibit the formation of zinc dendrites during galvanostatic cycling tests. The corrosion inhibitor BD endows the symmetric zinc-ion battery with a service life of 1000 h at 8 mA cm−2 for 5 mAh cm−2.

Development of an automated millifluidic platform and data-analysis pipeline for rapid electrochemical corrosion measurements: A pH study on Zn-Ni

We describe the development of a millifluidic based scanning droplet cell platform for rapid and automated corrosion. This system allows for measurement of corrosion properties (e.g., open circuit potential, corrosion current through Tafel and linear polarization resistance measurements, and cyclic voltammograms) on a localized section of a planar sample. Our system is highly automated and flexible, allowing for scripted changing and mixing of solutions and point-to-point motion on the sample. We have also created an automated data analysis pipeline. Here we demonstrate this tool by corroding a plate of electroplated Zn85Ni15 alloy over a range of pH values and correlate our results with XPS measurements and literature.

Micro Droplet Corrosion: Measuring Changes in Wetting and Surface Area during Electrochemical Measurements

Dynamic surface wetting that occurs during electrochemical droplet cell corrosion measurements on an Al alloy and Cu galvanic couple was monitored using the combination of a goniometer and potentiostat. The in situ observation of wettability during polarization of each metal and at the interface in 0.4 μL, 0.05 M NaCl aqueous droplets was performed. Droplet spreading was heterogeneously dynamic for measurements at the interface of the two metals due to the diffusion of oxygen from the surrounding environment into the droplet edges that was reduced on the cathodic metal, thus increasing the wettability on this region. The anodic metal served as a sacrificial anode and remained in a constant wetted state. Performing measurements under anaerobic conditions, where minimal changes in voltammetric response were observed, inhibited such dynamic wetting. All voltammetry was normalized by the surface area of the droplet footprint, which was measured after droplet evaporation instead of overestimating the corrosion current densities by assuming the droplet size to be same diameter as the pipette aperture. This work highlights the potential for the combined goniometer-electrochemical setup to further enhance the corrosion community’s knowledge about interfacial chemistry, the influence of surface preparation on droplet footprint size, and the importance of considering the dynamic evolution of micro/nanoscale droplets on heterogeneous substrates when estimating corrosion rates.

Quantitative measurement of corrosion at the nanoscale by in situ spectral modulation interferometry

This research study presents a novel application of a quantitative phase microscopy technique, spectral modulation interferometry (SMI), for in situ nanoscale characterization of corrosion of an aluminum alloy in real time. SMI offers high sensitivity, rapid image acquisition, and speckle-free images; thus, real-time quantification of surface topography evolution during corrosion can be obtained accurately to evaluate the temporally- and spatially-dependent corrosion rates. With an innovative additive-manufactured fluid cell, experiments were performed in situ under flowing solution conditions. Electrochemical tests via stepwise polarization and solution chemistry through collected aliquots of outflow solution were also performed alongside the nanoscale SMI experiment to simultaneously provide a corroborating corrosion rate measurement. Based on the quantitative 3D height profiles across the corroded surface, pit formation resulting from rapid local corrosion was predominant, appearing at different times and are heterogeneously distributed across the surface. The computed time-dependent dissolution rates of aluminum also varied as the experiment proceeded, with the combination of linear and nonlinear surface normal distributions. An initial mean linear dissolution rate of [0.40 ± 0.007] μmol m−2 s−1 transitioned to a more rapid mean rate of [1.95 ± 0.035] μmol m−2 s−1, driven by the anodic polarization. Dissolution rates from the three performed methods follow similar trends and there is the visibility of linking the nanoscale in situ SMI data to the electrochemical corrosion measurements and ex situ chemical solution analysis. At the end of the corrosion period, rates of 118 μmol m−2 s−1, 71 μmol m−2 s−1, and 2.45 μmol m−2 s−1 were obtained from electrochemical measurements, ex situ solution analyses, and in situ SMI corrosion measurement, respectively. Finally, these experimental results validate the applicability of SMI for in situ nanoscale characterization of a corroding alloy surface.

Imidazole derivatives based on glycourils as efficient anti-corrosion inhibitors for copper in HNO3 solution: Synthesis, electrochemical, surface, and theoretical approaches

Even though there are many synthesized structures that can be used to combat corrosion during the acid pickling process, the problem's persistence prompts modern corrosion scientists to seek deeper insights into the field by synthesizing more and more interesting moieties for practical applications and their applied capabilities against corrosion. The inhibition impacts of two imidazole derivatives fused ring based on glycourils, namely, Glycouril (tetrahydroimidazo[4,5- d ]imidazole-2,5(1 H,3 H)- dione) (3) and Dithioglycouril (tetrahydroimidazo[4,5- d ]imidazole-2,5(1 H,3 H)-dithione) (7)] on copper corrosion were investigated in stagnant aerated 1 M HNO 3 solutions at 25 °C. Surprisingly, there is no report on using glycouril (IMD-O) and/or dithioglycuril (IMD-S) as corrosion inhibitors for copper in acidic environment. The action of corrosion inhibiting of copper in 1 M HNO 3 for both compounds was explored by various electrochemical measurements, and the findings reveal that they all work as mixed-type corrosion inhibitors under the conditions that were studied. The results revealed the inhibitory effect of imidazole derivatives depends on their concentration. The examined imidazole derivatives displayed significant inhibitory efficiency (ex. 92.5 %) and played an important role in preventing copper corrosion in 1 M HNO 3 . The adsorption of the examined imidazole derivatives on copper surface in 1 M HNO 3 is followed Langmuir isotherm model. AFM investigation revealed a considerable improvement in the copper surface in the presence of imidazole derivatives, which protected the surface by forming an inhibitive coating over the copper surface. Furthermore, DFT calculations and Monte Carlo simulations on the active form of the synthesized imidazole derivatives were performed. The findings of the theoretical studies and electrochemical corrosion measurements are consistent with the microscopic results of the investigated imidazole derivatives based glycourils. The compounds in consideration could be a potential copper corrosion inhibitor in HNO 3 solutions, as they displayed superior corrosion inhibition properties to similar compounds and the inhibition efficiency increases in the following order IMD-O<IMD-S. • Imidazole derivatives based glycouril are investigated for the corrosion inhibition of copper in 1 M HNO 3 for the first time. • IMD-S is a good inhibitor for copper in 1 M HNO 3 at low concentration. • AFM results confirm those obtained by electrochemical measurements. • Theoretical studies confirm the performance of IMD-S.

Effect of hydrodynamics and laser surface melting on erosion-corrosion of X70 steel pipe elbow in oilfield slurry

Erosion-corrosion (EC) is a significant cause of pipeline failure in the petrochemical industry. The influence of laser surface melting (LSM) on the EC of API X70 steel was investigated with simulated oilfield slurry (1.5 wt% silica sand). The slurry was circulated continuously in a closed-loop apparatus at 3 m/s velocity and EC tests were performed using electrochemical corrosion and weight loss measurements for the untreated and LSM (2.5 kW) samples located at a 90⁰ pipe elbow. Since the erodent particle velocity and the flow rate are low, the EC was dominated by corrosion. LSM samples exhibited higher EC resistance and hardness due to the surface metallurgy alteration and the EC rate varies within the pipe elbow. The primary reasons for the severe EC rates of electrodes placed at the downstream side of the elbow's extrados (outer face) are the secondary flow effect and higher sand concentration.