2-Mercaptobenzoxazole as a copper corrosion inhibitor in chloride solution: Electrochemistry, 3D-profilometry,and XPS surface analysis

2-Mercaptobenzoxazole (MBOH) was studied as a corrosion inhibitor for Cu in 3 wt.% NaCl solution using EIS, a potentiodynamic curve, 3D-profilometry, and XPS measurements. It was shown that Cu corrosion in solution containing MBOH follows kinetic-controlled and diffusion-controlled processes and that MBOH is a mixed-type inhibitor. The diffusion coefficient of the Cu ions travelling through the solid surface layers was estimated to be on the order of 10⁻¹⁵–10⁻¹⁴ cm² s⁻¹. It was also demonstrated that the Cu(I)–MBOH complex is formed on the Cu surface and that the thickness of this surface layer is 1.4 ± 0.4 nm.     

Sulphuric acid corrosion of ultrafine-grained mild steel processed by equal-channel angular pressing

A bulk ultrafine-grained (UFG) mild steel with a ferrite grain size of approximately 200 nm and a dispersed distribution of iron carbide particles was fabricated by equal-channel angular pressing (ECAP) at 400 °C. The corrosion behaviour of the ECAP-processed mild steel and pure iron was investigated in a 0.5 mol/L H₂SO₄ solution. They exhibited a higher corrosion rate and better anodic passivity properties due to the presence of more crystalline defects. As a result of the refinement of the iron carbide particles, the forming ability of a continuous dense passive film was improved.     

Orientation dependence of the electrochemical corrosion properties of electrodeposited Cu foils

In this study, the electrochemical corrosion properties of electrodeposited Cu foils in a CuCl₂-containing acidic etching solution were investigated. The main passive product was CuCl and a trace amount of Cu₂O can also be detected. The (2 2 0)-oriented Cu foils exhibited higher corrosion potential and lower corrosion current density than those with (1 1 1) or (2 0 0) texture, suggesting a superior corrosion resistance against the etching solution. It is proposed that the preferred orientation and thus the differences in atomic stacking density on specific planes dominated the corrosion properties of the electrodeposited Cu foils instead of grain size or surface roughness.     

Long-term monitoring of atmospheric corrosion at weathering steel bridges by an electrochemical impedance method

Weathering steel corrosion was monitored for one to two years under natural atmosphere by an electrochemical impedance technique. Two identical comb-shape weathering steel sheets embedded in epoxy resin were used as monitoring probe electrodes at two different bridges in Japan. Impedances at 10 kHz (Z_10kHz) and 10 mHz (Z_10mHz) were automatically measured every hour. Coupons (50 × 50 × 2 mm³) prepared from the same steel sheets were exposed together to measure the corrosion mass loss. The average (Z_10mHz)⁻¹ value for half to one year exposure correlated well with the average corrosion rate determined from the corrosion mass loss.     

Corrosion of ultra-high-purity Mg in 3.5% NaCl solution saturated with Mg(OH)2

Corrosion was evaluated for ultra-high-purity magnesium (Mg) immersed in 3.5% NaCl solution saturated with Mg(OH)₂. The intrinsic corrosion rate measured with weight loss, P_W = 0.25 ± 0.07 mm y⁻¹, was slightly smaller than that for high-purity Mg. Some specimens had somewhat higher corrosion rates attributed to localised corrosion. The average corrosion rate measured from hydrogen evolution, P_AH, was lower than that measured with weight loss, P_W, attributed to dissolution of some hydrogen in the Mg specimen. The amount of dissolution under electrochemical control was a small amount of the total dissolution. A new hydride dissolution mechanism is suggested.     

2-Mercaptobenzimidazole as a copper corrosion inhibitor: Part I. Long-term immersion, 3D-profilometry,and electrochemistry

The high corrosion inhibition effectiveness of 2-mercaptobenzimidazole (MBIH) in 3 wt.% aqueous NaCl solution is reported using long term immersion tests, 3D-profilometry, electrochemical impedance spectroscopy, and potentiodynamic curve measurements. The high corrosion inhibition performance was proven after 180 days of immersion. The impedance spectra were characterized by two time constants relating to charge transfer and finite layer thickness or semi-infinite diffusion of copper ions through the surface layer, therefore Cu corrosion in solution containing MBIH follows kinetic-controlled and diffusion-controlled processes. Moreover, it is shown that MBIH is a mixed-type inhibitor.     

Corrosion behaviour of Al–29at%Co alloy in aqueous NaCl

Microstructure and corrosion behaviour of a binary Al–29 at%Co alloy have been studied. The alloy was prepared by arc-melting of Al and Co in high purity Ar and rapidly solidified on a water-cooled Cu mould. The alloy chemical composition and microstructure were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Furthermore, the corrosion behaviour was studied by potentiodynamic polarization in aqueous NaCl (0.6 mol dm⁻³) at room temperature. The alloy was found to consist of three phases: hexagonal Al₅Co₂, Z-phase and AlCo (β). The corrosion resistance of different intermetallic phases is characterized. The results are compared to previously published results of Al–TM (TM = transition metal) alloys.     

The effect of precipitate size on the yield strength-pitting corrosion correlation in Al–Cu–Mg alloys

The effect of precipitate size and state on the combinations of yield strength and corrosion pit susceptibility exhibited by a model aluminum alloy Al–2.5Cu–1.5 Mg (wt.%) has been measured for the first time. For aging times less than 2 h at 200 °C, it is shown that the fine nanoscale precipitates that form strongly affect the yield stress of the alloy but do not contribute to electrochemical heterogeneity that leads to corrosion susceptibility. This illustrates that a precipitate size range exists where the usually observed inverse correlation between strength and corrosion resistance can be broken. At longer aging times, when the precipitates become larger, a three orders of magnitude increase in the pitting rate is observed between aging times of 2 h and 9 h. The step change in pitting rate corresponds with a critical precipitate size lying between ～3 nm and 8 nm and it is hypothesized that this size corresponds to a critical size above which it is not possible for the formation of a continuous protective passive oxide film to occur.     

Corrosion behavior of Cu during graphene growth by CVD

The corrosion performance of Cu samples may be affected by annealing at high temperatures during graphene growth via the chemical vapor deposition method. In this study, multiple graphene films were deposited on Cu and characterized by Raman spectroscopy and transmission electron microscopy. The corrosion behavior of Cu immersed in 3.5 wt.% NaCl solution was investigated using electrochemical impedance spectroscopy. The Cu morphology was observed by optical microscopy and scanning electron microscopy. Results indicated that annealing affects the corrosion process of Cu. The presence of graphene films on the Cu substrate improved the corrosion performance of the material for a short period of time.     

Estimation of residual corrosion rates of steel under cathodic protection in soils via voltammetry

Steel coupons were buried in soil for 2 months under cathodic protection. Their residual corrosion rates were deduced from voltammetry and weight loss measurements. In aerated soils, the current density due to O₂ reduction, j_K,O2, was modelled with a mixed activation–diffusion controlled kinetic. The anodic part j_A of the current density j, computed as j_A = j − j_K,O2, obeyed Tafel law. Its extrapolation to the protection potential gave a corrosion rate (∼7 μm yr⁻¹) consistent with that obtained from weight loss measurements. With a deficient protection, corrosion rates remained at ∼80 μm yr⁻¹, a value given by both methods.     

Electrochemical behavior of a lead-free Sn–Cu solder alloy in NaCl solution

Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization techniques and an equivalent circuit analysis are used to evaluate the electrochemical corrosion behavior of Sn–Cu alloy samples in a naturally aerated 0.5 M NaCl solution at 25 °C. It has been found that a better electrochemical corrosion resistance is provided by a coarser cellular microstructure array. It has also been found that the corrosion current density (i_corr) is of about a quarter when compared with that of the finest microstructure examined. Such behavior is attributed to both localized strains between the Sn-rich phase and intermetallic (IMC) particles and the cathode/anode area ratios. The effect of copper alloying on i_corr is also discussed.     

2-Mercaptobenzimidazole as a copper corrosion inhibitor: Part II. Surface analysis using X-ray photoelectron spectroscopy

In Part I of this study, the high corrosion inhibition effectiveness of 2-mercaptobenzimidazole (MBIH) in 3 wt.% NaCl solution was unambiguously proven. In Part II, using angle-resolved X-ray photoelectron spectroscopy (XPS), the surface chemical structure and composition of adsorbed MBIH on Cu from the same solution was investigated. It was found that MBIH molecules are directed toward the Cu surface through their N and S atoms. The MBIH layer thickness is 1.9 ± 0.5 nm, as determined from a detailed analysis of the background in the XPS spectra. Tentative MBIH orientations on Cu were suggested based on the XPS measurements.     

Hydroxymethyl urea and 1,3-bis(hydroxymethyl) urea as corrosion inhibitors for steel in HCl solution

The inhibition effect of two urea derivatives of hydroxymethyl urea (HMU) and 1,3-bis(hydroxymethyl) urea (BHMU) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS), quantum chemical calculation and molecular dynamics (MD) simulation methods. Inhibition efficiency values of 20.0 mM HMU and BHMU are higher than 80% and 85% at 20–50 °C, respectively. The adsorption of each inhibitor on steel surface obeys Langmuir adsorption isotherm, and is mainly the chemical adsorption. Inhibition efficiency follows the order: BHMU > HMU.     

Effect of small amounts of alloyed tin on the electrochemical behaviour of aluminium in sodium chloride solution

Binary model AlSn alloys containing 30–1000 ppm (by weight) Sn were investigated by electrochemical polarization in 5 wt% chloride solution and subsequent characterization of corrosion morphology. In the homogenized and rolled condition, tin concentration only slightly affected electrochemical behaviour up to 500 ppm, and the pitting potentials were all about −0.8 V_SCE. However, alloy containing 1000 ppm Sn was significantly activated by lowering of the passivity-breakdown potential to −1.38 V_SCE. Annealing at 300 °C caused significant segregation of Sn to the metal surface, and all specimens, independent of bulk Sn concentration, became nearly similarly active with breakdown potentials around −1.2 V_SCE. Corrosion on 300 °C-annealed specimens was uniformly distributed by polarization below the bulk pitting potential of −0.76 V_SCE. Moreover, the activation effect was temporary, and corrosion was significantly reduced as the segregated Sn was etched away from the surface. Thick oxide, formed during water quenching on high Sn concentration samples, containing 500 and 1000 ppm Sn, introduced partial passivation during polarization test. Annealing at 600 °C caused increasing activation with increasing Sn concentration, caused by Sn enrichment at the metal surface by dealloying of aluminium during anodic polarization in chloride solution. Corrosion was localized in the form of grain boundary corrosion for alloyed Sn concentration less than and equal to 500 ppm and pitting following the triple grain boundaries for 1000 ppm.     

Mechanistic studies of corrosion product flaking on copper and copper-based alloys in marine environments

The mechanism of corrosion product flaking on bare copper sheet and three copper-based alloys in chloride rich environments has been explored through field and laboratory exposures. The tendency for flaking is much more pronounced on Cu and Cu–4 wt%Sn than on Cu–15 wt%Zn and Cu–5 wt%Al–5 wt%Zn. This difference is explained by the initial formation of zinc and zinc–aluminum hydroxycarbonates on Cu15Zn and Cu5Al5Zn, which delays the formation of CuCl, a precursor of Cu₂(OH)₃Cl. As a result, the observed volume expansion during transformation of CuCl to Cu₂(OH)₃Cl, and concomitant corrosion product flaking, is less severe on Cu15Zn and Cu5Al5Zn than on Cu and Cu4Sn.     

Corrosion fatigue crack growth behavior of oil-grade nickel-base alloy 718. Part 1: Effect of corrosive environment

The effect of corrosive environment on corrosion fatigue crack growth (CFCG) behavior of oil-grade nickel-base alloy 718 is studied. The results demonstrate that there is no obvious effect of 3.5 wt.% NaCl solution at RT, 50 °C and 80 °C on CGCG rates while 21 wt.% NaCl solution at 80 °C produces a deleterious effect on CFCG rates compared to the ones tested in air. Potentiodynamic polarization results show that alloy 718 exhibits passive behavior in 3.5 wt.% NaCl solution, while pitting corrosion resistance decreases with increasing solution temperature. Nevertheless, alloy 718 shows active corrosion behavior in 21 wt.% NaCl solution at 80 °C.     

Adsorption and corrosion inhibition of phytic acid calcium on the copper surface in 3 wt% NaCl solution

The adsorption and corrosion protection effect of phytic acid calcium (PAC) film on the copper surface in 3 wt% NaCl solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Raman spectroscopy. Polarization curves indicate that PAC is a mixed inhibitor, affecting both cathodic and anodic corrosion currents. The inhibition efficiency of PAC film reached 92.53% at an optimized condition. Adsorption of PAC molecules on the surface followed Langmuir adsorption isotherm and the standard Gibbs energy of −37.32 kJ mol⁻¹ indicated a chemisorptive way. Raman studies suggested that PAC molecule chemically anchored at the surface via PO groups.     

Characterization of corrosion products formed on Ni 2.4 wt%–Cu 0.5 wt%–Cr 0.5 wt% weathering steel exposed in marine atmospheres

Weathering steel manufactured with high concentrations of copper (0.5 wt%), chromium (0.5 wt%) and nickel (2.4 wt%) was studied with the aim of furthering knowledge on corrosion product characterization and performance in marine environments. Specimens exposed for two years in a rural atmosphere and two marine environments were characterized by optical microscopy, SEM/EDS, XRD and Raman spectroscopy and corrosion rates measured. The main phases found were ferrihydrite, maghemite and goethite in the inner corrosion layer, and lepidocrocite in the outer layer. Cu and Ni were homogeneously distributed while Cr tended to be concentrated in the inner layer.     

The effect of grain refinement on the adhesion of an alumina scale on an aluminide coating

To understand the effect of grain refinement on the thermally grown alumina scale adhesion to the metal substrate, two δ-Ni₂Al₃ coatings, one coarse-grained (∼70 μm) and the other ultrafine-grained (generally below ∼500 nm), were prepared. The cyclic oxidation in air at 1100 °C shows that the ultrafine-grained (UFG) coating is better oxidation resistant than the coarse-grained (CG) coating due to the formation of a more adherent alumina scale. The latter is intrinsically correlated with the fact that the aluminide grain refinement helps to increase the oxide/metal strength through a route to prevent the formation of large-sized voids at the interface.     

Adsorption and inhibition effect of Ascorbyl palmitate on corrosion of carbon steel in ethanol blended gasoline containing water as a contaminant

The adsorption and inhibition effect of Ascorbyl palmitate (AP) on carbon steel in ethanol blended gasoline containing water as a contaminant (GE10 + 1%water) was studied by weight loss and electrochemical impedance spectroscopic (EIS) techniques. The results showed that the addition of ethanol and water to gasoline increase the corrosion rate of carbon steel. AP inhibits the corrosion of carbon steel in (GE10 + 1% water) solution to a remarkable extent. The adsorption of AP on the carbon steel surface was found to obey the Langmuir adsorption isotherm model. The values of activation energy (E_a) and various thermodynamic parameters were calculated and discussed.