Interfacial Corrosion Research Articles

Interface corrosion behavior of copper-aluminum laminated composite plates in neutral salt fog

The corrosion behavior of pure copper, aluminum, and Cu–Al laminated composite plates produced through semi-molten continuous casting and rolling exposed to salt fog were evaluated. The copper performed the best corrosion resistance, then the aluminum. At first a corrosion belt occurred along the interface next to the diffusion layer (intermetallic) at the preliminary stage on the aluminum side, the generated cracking corrosion products formed an another galvanic cell with surrounding aluminum matrix, where the aluminum as the anode, and then pits appeared on the aluminum near the interface and gradually expanded to larger and deeper holes, while some small holes appeared on the other areas of aluminum as the process went on, and then corrosion products exerted stress on the surface of grain to come up denudation. Finally, localized corrosion gradually developed to general corrosion. Besides, with the extension of corrosion time, the corrosion rate of Cu–Al firstly decreases, then increases and finally decreases again.

Effect of exfoliated few-layered graphene on corrosion and mechanical behaviour of the graphitized Al–SiC surface composite fabricated by FSP

The influence of friction stir processing parameters and the subsequent evolution of microstructures and corrosion behaviour of Al–SiC surface composites fabricated in the presence of graphitic flakes are presented in this paper. The circumferential shear stress exerted by the rotating tool exfoliates the graphite flakes into few-layered graphene during processing. These graphene flakes preferentially occupy both the grain boundaries and the SiC–Al interface during recrystallization. The potentiodynamic polarization test, in 3.5 wt% sodium chloride (NaCl) solution, is conducted for samples processed at various tool rotational speeds and it is found that the presence of this thin graphitic layer at these locations reduces the intergranular and interfacial corrosion to a great extent. The tool rotational speed has a significant influence on processing, and samples fabricated at an optimum tool rotational speed of 2200 rpm shows better corrosion resistance and mechanical properties as compared to that at lower and higher speeds. Raman spectroscopic analysis, X-ray diffraction studies and microhardness tests corroborate the experimental results and the proposed mechanisms.

Failure Analysis of Brazed Joints—A Case Study

Heat exchangers presented water leaking at brazed joints. The first was exposed to water–salt solution, and both interfacial and crevice corrosion were found being the cause of failure. The second heat exchanger was not in function when a water leaking evidenced an interfacial corrosion.

Interaction of interfacial debonding and under-film corrosion propagation at the edge of the blistering area of epoxy coating

Interaction of interfacial debonding and under-film corrosion propagation at the edge of the blistering area of epoxy coating

Liquid-Air Interface Corrosion of A537 Steel in High Level Liquid Radioactive Waste Simulant in a Sealed Container

Liquid-air interface (LAI) corrosion is regarded as a potential issue for interim storage tanks of high level liquid radioactive waste. Insightful studies have been carried out and several hypotheses have been proposed so far, while none has been directly confirmed experimentally. A sealed container has been developed to investigate the effect of atmosphere on LAI corrosion of partially immersed A537 steels, in which the composition and temperature of air can be changed accordingly, i.e. CO2 concentration varied between 0.05 wt% (natural air) and 1.97 wt%, and temperature varied between 25°C and 34°C. It has been found that the pitting initiation process under both anodic polarization and free immersion conditions can be largely accelerated by the increase of CO2 concentration. More importantly, a planar pH electrode has been applied to measure pH at the interface during anodic polarization and free immersion, and the occurrence of LAI corrosion can be correlated with the same interface pH at a certain temperature regardless of CO2 concentration, indicating a “critical pH” for LAI corrosion determined by this method. This finding suggests that LAI corrosion in high level liquid radioactive waste may be investigated through determination of a critical pH in certain circumstances.

Low Stress Abrasion-Corrosion of High-Cr White Cast Iron: Combined Effects of Particle Angularity and Chloride Ions

Tribo-electrochemical behavior of a high chromium white cast iron (high-Cr WCI) used in, e.g., slurry pumps in mining and mineral processing applications, was investigated using a combination of electrochemical techniques, including zero resistance amperometry as well as potentiostatic and potentiodynamic polarisation. The effects of third body particles angularity on the localised tribocorrosion response of the cast alloy was studied during and post abrasion-corrosion by round ceramic beads and semi-angular silica sand particles. Advanced characterization methods such as electron backscatter diffraction and focused-ion beam cross-sectioning of affected areas were also employed to understand the wear and corrosion interactive actions. It was found that in chloride-free solutions, the behavior of high-Cr WCI resembled that of the austenitic 316 SS studied before. In contrast, in chloride-containing electrolytes, the semi-angular silica sand particles increased interfacial (carbide/matrix) localised corrosion susceptibility during and post-abrasion as indicated by the stark increase in anodic current and the morphology of the attack. Semi-angular silica sand abrasives had a greater adverse impact on post-abrasion interfacial corrosion vulnerability, compared to round ceramic beads. The complex behavior observed indicates that any material developed for tribocorrosive conditions must account for the particles angularity and their subsequent effects on localised corrosion.

Influence of High-Density electropulsing treatment on the interface corrosion characteristics of 316L steel in Lead-Bismuth eutectic at 823 K

In order to find an effective method to improve the corrosion resistance properties of the candidate structural materials for lead-alloy cooled fast reactors, the 316L steel was treated by high density single elec-tropulsing. And then the interface corrosion characteristics in stagnant lead-bismuth eutectic (LBE) at 823 K for 1000 h were examined. The results show that electropulsing treatment (EPT) has a significant influence on microcosmic appearance and corrosion depth of the corroded specimens. All the specimens were subjected to dissolution corrosion, but EPT with a current density of 1828 A mm-2 can improve obviously the corrosion resistance and reduce the extent of local corrosion of 316L in LBE. In addition, the corrosion depth of the 1828 A mm-2 EPT specimen decreases by 38%, compared with that of the non-EPT specimens.

Interfacial characteristics of Zn/AZ31/Zn clad sheets fabricated by hot roll-bonding and annealing

ABSTRACTThe Zn/AZ31/Zn tri-layer clad sheets are prepared by hot roll-bonding technology and post-roll annealing in this study and the interfacial microstructure, mechanical and corrosion properties are investigated. The annealing temperature can influence the interfacial bonding behaviour. Upon annealing at 200°C, a good metallurgical bonding interface composed of Mg4Zn7 and MgZn2 phases is obtained. A higher temperature (300°C) can induce the precipitation of the brittle Mg2Zn11 phase at the interface. The clad sheets annealed at 200°C can attain the maximum bonding strength among all the clad sheets investigated. Importantly, the corrosion rate can be obviously reduced by cladding pure Zn layer on both sides of AZ31 alloys, which provides another effective method to improve the corrosion resistance of magnesium alloys.

Experimental, density functional theory and molecular dynamics supported adsorption behavior of environmental benign imidazolium based ionic liquids on mild steel surface in acidic medium

This study describes the adsorption behavior of three 1-butyl-3-methyl-imidazolium ionic liquids namely, 1-butyl-3-methylimidazolium chloride ([bmim][Cl]), 1-butyl-3-methylimidazolium acetate ([bmim][Ac]) and 1-butyl-3-methylimidazolium trifluoromethanesulphonate ([bmim][CF3SO3]) at mild steel/1 M HCl interface using experimental and computational studies. Electrochemical and gravimetric measurements revealed that the inhibition efficiency of the studied ionic liquids increases with increase in concentrations, such that [bmim][Cl], ([bmim][CF3SO3] and [bmim][Ac]) gave the maximum inhibition efficiencies of 93.18%, 96.02% and 97.15%, respectively at a concentration as low as 8.67 × 10−4 mol L−1. The studied ionic liquids act as interfacial corrosion inhibitors and their adsorption at mild steel/electrolyte interface obeyed the Temkin adsorption isotherm. Polarization study suggested that the ionic liquids are mixed-type corrosion inhibitors. SEM and AFM analyses were undertaken to support the adsorption of the ionic liquid molecules on mild steel surface in 1 M HCl solution. Orientation and adsorption mode of 1-butyl-3-methyl-imidazolium molecules on mild steel surface was investigated using molecular dynamic (MD) simulations, which revealed that 1-butyl-3-methyl-imidazolium molecules adsorb on mild steel surface in flat orientations. Quantum chemical parameters for the neutral and protonated forms of the ionic liquids as well as the binding energies and radial distribution function indices obtained from molecular dynamic simulations corroborate the experimental results.

Interfacial corrosion of copper in concentrated chloride solution and the formation of copper hydroxychloride

This work aims to investigate the waterline corrosion of pure copper in 4 M NaCl solution. Three distinct regions are identified. Corrosion products formed at the waterline are characterized by micro-Raman spectroscopy, complemented by SEM/EDS, as a function of immersion time. The co-existence of four copper species is explained by thermodynamic equilibrium consideration. The composition of spreading region is determined and compared with the oxide film formation in different pH NaOH solutions. The anodic dissolution of copper exposed to the bulk electrolyte is investigated by electrochemical methods. The pH and potential profiles across three regions are proposed.

Study of Nano-Mechanical, Electrochemical and Raman Spectroscopic Behavior of Al6061-SiC-Graphite Hybrid Surface Composite Fabricated through Friction Stir Processing

Aluminium-based hybrid metal grid composites (MMC) are extensively utilized in automobile applications (engine cylinders, pistons, etc.) as they exhibit a fantastic blend of properties. Here, a detailed study of nano-mechanical, electrochemical and Raman spectroscopic behavior of friction stir processed Al6061-SiC-graphite hybrid surface composite is presented. The effect of various tool rotational speeds was evaluated along with the monitoring of variation in axial force. Microstructural changes with various tool rotational speeds are studied by using a scanning electron microscope. Raman spectroscopy and X-Ray diffraction studies are used for the spectroscopic characterization of the fabricated hybrid and mono surface composites. Residual stresses and various crystal structure disorders of reinforcement result in the significant change in intensity and a considerable shift in Raman peak positions. The nano-mechanical behavior of the fabricated composite with various reinforcements and tool rotational speeds are analyzed by using nano-indentation. The nano-mechanical behavior of hybrid composite fabricated with an optimum set of processing parameters is superior to mono composites fabricated with the same processing parameters. Also, the electrochemical behavior of the fabricated composites is studied by linear potentiodynamic polarization test. The Al6061-SiC-graphite hybrid surface composite reveals excellent nano-mechanical and electrochemical behavior when fabricated with an optimum set of processing parameters. The tool rotational speed has a pronounced effect on the dispersion of agglomerates and grain refinement of the matrix material. The processing parameters extensively affect the Raman spectroscopic behavior of the hybrid composite. The hybrid surface composite shows better corrosion resistance than the mono composites when fabricated with an optimum set of processing parameters. Reduced intergranular as well as interfacial corrosion pits in hybrid composites increased its resistance to corrosion.

Technical Note: Syringe Cell for Electrochemical Testing

A very simple electrochemical cell for corrosion experiments has been developed using a syringe as the cell with the syringe plunger replaced by reference and counter electrodes. Because the exposed area is defined by a hanging droplet, no masking is required and thus no crevice corrosion forms. This cell therefore enables measurements of pitting potentials of metals that are susceptible to crevice corrosion. The method was validated by cyclic potentiodynamic polarization experiments on Type 304H stainless steel. Crevice or interfacial corrosion was not evident in multiple replicate specimens tested with the syringe cell method.

Unexpected Interface Corrosion and Sensitization Susceptibility in Additively Manufactured Austenitic Stainless Steel

This communication describes observations of unexpected microstructural interface susceptibility to accelerated dissolution in additively manufactured (AM) Type 316L stainless steel prepared by selective laser melting. Observations include accelerated microstructural interface dissolution in the as-built condition, as well as more rapid sensitization of grain boundaries upon exposure to elevated temperature. Electrolytic etching in persulfate solution was used to evaluate the susceptibility of microstructural interfaces to accelerated dissolution in both wrought and AM 316L. Post-test optical microscopy and profilometry on AM 316L revealed that the melt pool boundaries in the as-built condition were susceptible to accelerated attack, although the small grains within the prior melt pools were not. Furthermore, short, elevated temperature exposure (1 h at 675°C) also induced sensitization of the grain boundaries. Identical testing on as-manufactured wrought 316L confirmed that no microstructural interfaces showed susceptibility to accelerated dissolution, and grain boundaries could be sensitized only by extended periods (24 h) at elevated temperature (675°C). Annealing was capable of removing sensitization in wrought 316L, but activated the surface of the AM 316L, leading to widespread, uniform dissolution.

Synthesis, characterization and corrosion inhibition studies of N-phenyl-benzamides on the acidic corrosion of mild steel: Experimental and computational studies

Present study aims to demonstrate the effect of electron withdrawing nitro (NO2) and electron releasing methoxy (OCH3) substituents on the inhibition behavior of N-Phenyl-benzamide derivatives (BNAs), namely N-(4-nitrophenyl) benzamide (BNA-1; NO2), N-phenylbenzamide (BNA-2; H) and N-(4-methoxyphenyl)benzamide (BNA-3; OCH3) for mild steel acidic (1M HCl) corrosion. Results of the computational and experimental studies showed that methoxy (OCH3) substituent enhances the inhibition efficiency whereas nitro (NO2) decreases the inhibition efficiency. Electrochemical impedance spectroscope (EIS) study showed that BNAs acted as interface corrosion inhibitors and polarization study shows they acted as cathodic type corrosion inhibitors. They showed maximum efficiencies of 89.56%, 93.91% and 96.52% for BNA-1, BNA-2 and BNA-3, respectively. The BNAs strongly (high Kads values) and spontaneously (negative ∆G0 values) adsorbed at metal/electrolyte interfaces and their mode of adsorption obeyed the Langmuir adsorption isotherm. Surface investigation of the mild steel surfaces using AFM and SEM analyses revealed that BNAs adsorb on the surface and increase the energy barrier for corrosive dissolution which is also supported by the higher values of Ea (activation energy). DFT study carried out using 3-21G, 6-31G and 6-311G basis sets provides significant support to the experimental efficiency order. DFT indices like EHOMO, ELUMO, electronegativity (χ), softness (σ), hardness (η), dipole moment (μ), energy band gap (∆E) and fraction of electron transfer (∆N) were derived for all basis sets. Experimental and DFT study was further supported by molecular dynamic (MD) simulations study.

Synthesis, characterization and corrosion inhibition properties of benzamide–2-chloro-4-nitrobenzoic acid and anthranilic acid–2-chloro-4-nitrobenzoic acid for mild steel corrosion in acidic medium

The present study deals with the synthesis of two new compounds namely, benzamide – 2-chloro-4-nitrobenzoic acid (BENCNBA) and anthranilic acid–2-chloro-4-nitrobenzoic acid (AACNBA) using solid phase reactions. The phase diagram studies revealed that formation of the investigated compounds occurs in 1:1 molar ratio. The synthesized compounds were characterized using several spectral techniques such as FT-IR, 1H and 13C NMR, UV–Vis, powder X-ray diffraction (PXRD). Single crystal XRD (SCXRD) study showed that both BENCNBA and AACNBA compounds crystallize in triclinic crystal system with P-1 space group. Further, the presence of intermolecular hydrogen bonding between the constituent components was also supported by single crystal X-ray diffraction (SCXRD) method. Heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions have also been computed using the enthalpy of fusion values derived from differential scanning calorimeter (DSC) study. The inhibition effect of BENCNBA and AACNBA on the mild steel corrosion in hydrochloric acid solution was tested using electrochemical methods. Electrochemical impedance spectroscopy (EIS) study revealed that both BENCNBA and AACNBA behaved as interface corrosion inhibitors and showed maximum inhibition efficiencies of 95.71% and 96.42%, respectively at 400 ppm (1.23 × 10−3 M) concentration. Potentiodynamic polarization (PDP) measurements suggested that BENCNBA and AACNBA acted as mixed type corrosion inhibitors. EIS and PDP results showed that BENCNBA and AACNBA act as efficient corrosion inhibitors for mild steel and their inhibition efficiencies enhances on increasing their concentrations.

Microscopic Analysis and Electrochemical Behavior of Fe-Based Coating Produced by Laser Cladding

The effect of laser cladding on the surface microstructure and corrosion properties of coated/uncoated specimens were investigated. Fe-based alloy coating was produced on 35CrMo steel by laser cladding. The phase composition, microstructure, interface element distribution, microhardness and corrosion resistance of the cladding coating were measured. The results show that the cladding layer is mainly composed of α-Fe phases, the microstructure presents a gradient distribution, and a good metallurgical bond is formed at the boundary with the substrate. Microhardness profiles show that the average microhardness of the cladding coating is about 2.1 times higher than that of the uncoated specimen. In addition, the electrochemical results show that the coated specimen exhibits far better corrosion resistance than to the uncoated specimen.

Investigation of strength degradation of adhesive-bonded aluminum joints exposed to corrosive environment using electrochemical methods

Interfacial corrosion is responsible for the strength degradation of adhesive-bonded aluminum joints (ABJs) exposed to corrosive environment. In this study, electrochemical noise and electrochemical impedance spectroscopy (EIS) measurements were performed on the aluminum alloy X610-T4PD covered with adhesive (ACA) to understand the interfacial corrosion. And environmental simulation tests (i.e. neutral salt spray (NSS) and hot humidity environment) for ABJ were carried out to investigate the joint strength degradation. Test results indicated that the variations of current and potential in the EN measurement were closely related to the initiation of corrosion in the samples. The Nyquist plots in the EIS measurement for various immersion times showed that the corrosion of ACA accelerated after about 140 h. Furthermore, a linear relationship between the residual strength of ABJ exposed to NSS and the reciprocal of interfacial corrosion resistance (Rt) of ACA was found, which was verified by ABJ exposed to hot humidity environment.

Preparation and Characterization of TiN-SBR Coating on Metallic Bipolar Plates for Polymer Electrolyte Membrane Fuel Cell

In order to reduce interfacial contact resistance (ICR) and enhance corrosion resistance of 310 stainless steel (310 SS) for bipolar plates (BPs) of polymer electrolyte membrane fuel cell (PEMFC), TiN with styrene-butadiene rubber (SBR) coating was prepared by using electrophoretic deposition. Microstructure of TiN-SBR coated 310 SS prepared under different conditions was characterized by scanning electron microscopy (SEM), and a uniform, dense and well-bonded TiN-SBR coating was prepared at 30 V for 10 s in the suspension liquid containing 6.0 g/L SBR. Polarization behavior in the simulated service environment of PEMFC (1 M H2SO4 at 298 K) and ICR of the TiN-SBR coating deposited under the optimized conditions were investigated. The results showed that the TiN-SBR coating successfully decreased the anodic polarization current and ICR, indicating excellent interfacial contact resistance and corrosion resistance.

(Keynote) Organic Coatings for Corrosion Protection: Self-Healing at the Delaminated Interface

Recently significant progress has been made in developing self-healing coating systems capable of healing even macroscopic defect sites (see e.g. [1-3]). The corrosion triggered release and transport of sufficient amounts of inhibitors and/or self-healing agents to the defect site is enabled by the delamination of the coating. This allows fast spreading of the trigger signal, such as change of pH or potential, into the coating and also fast transport of the released active agents along the delaminated interface. However, when corrosion in the defect site is successfully inhibited it is important that also at the delaminated interface corrosion is inhibited and adhesion between metal and the organic coating is re-established again. Our knowledge of how to do this is still limited. Recent progress on this topic will be presented and discussed. [1] D. Crespy, K. Landfester, J. Fickert, and M. Rohwerder, Self-Healing Materials 273 (2016) 219-245. [2] T.H. Tran , A. Vimalanandan , G.Genchev , J. Fickert , K. Landfester , D. Crespy , M.Rohwerder, Advanced Materials 27(25) (2015) 3825-3830. [3] A. Vimalanandan, L.P. Lv, T.H. Tran, K. Landfester, D. Crespy, M. Rohwerder, Advanced Materials 25(48) (2013) 6980-6984.

Micro-PIXE study of metal loss from dental amalgam

Mercury amalgams have been a topic of controversy ever since their introduction over 150years ago as a dental material. An interesting question is if metals are released from the amalgam into the enamel and dentine tissue. To elucidate this PIXE mapping was used to investigate metal redistribution in an extracted molar tooth with a ∼30year old high-Cu content amalgam filling. The tooth was sectioned and polished, and elemental mapping carried out on the amalgam/enamel, bulk amalgam and the wear surface of the amalgam. As expected, the amalgam was multiphase amalgam comprising of Cu-rich and Ag-rich grains with non-uniform distribution of Hg. The amalgam/dentine interface was clearly defined with amalgam elements on one side and C and P from hydroxyapatite on the other side with evidence of only slight interface corrosion. The peaks for Cu Hg and Zn were isolated from interfering signals with concentrations in the enamel tissue, observed to be at, or below the method detection limit. The proximity in energy of the Sn Lαand Ca Kα, peaks and the background on the Hg Mα gave signal overlap which increased the MDL for these elements. Remarkably, a course grain texture in the amalgam was observed just below the biting surface of the amalgam which might be associated with tribochemical processes from mastication. This coupled with the clear absence of the amalgam metals from tooth tissue, even in close proximity to the interface, suggests that for this sample, release of Hg occurred via erosion or dissolution in saliva.