Corrosion behaviour of lead-copper alloys in sulphuric acid for battery applications

The corrosion behaviour in sulphuric acid of monotectic Pb-63 wt % Cu, hyper-monotectic Pb-30 wt % Cu, and Pb-10 wt % Cu was investigated and compared to that of Cu, Pb, as well as Pb–Ca, and Pb–Ca–Sn battery-grid alloys. On anodic polarization of pure Cu and Pb–Cu alloys. dissolution of the copper phase markedly increases as the potential is increased above the Cu/Cu²⁺ reversible potential, which is above the passive potential for lead and lead battery-grid alloys. A limiting current and pseudo-passive transition attains, and the pseudo-passive current decreases with decreasing bulk copper content of the alloy. Extensive selective leaching of copper from the 30 wt % Cu alloy produced a highly porous layer of spongy lead, and the subsequent anodic polarization behaviour (without repolishing the sample surface) showed a reduction in pseudo-passive corrosion rates to values 20 times greater (referred to unit geometric area) than the passive current of pure Pb and lead battery-grid alloys. This difference was attributed partly to dissolution of redeposited copper but mainly to the large effective surface area of the remaining porous lead network. The possible use of Pb–Cu alloys as high-conductivity battery-grid alloys is discussed.     

Effect of chloride concentration range on the corrosion resistance of Cu–xNi alloys

The anodic behaviour of Cu–xNi alloys and Cu and Ni metals was studied in slightly alkaline solutions containing Cl–-ions in the concentration range from 0.01 to 2.0moldm–3. The morphology and composition of the surface films formed by anodic polarization were analysed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). On the basis of quasi-potentiodynamic polarization data, Ec against cNaCl diagrams were constructed, where Ec is the critical pitting potential. These diagrams allow the determination of areas where the materials are susceptible to localized pitting attack. A critical chloride concentration (ccrit) exists below which the resistance to localized corrosion increases with decreasing nickel content and above which it increases with increasing nickel content. This effect is connected with the change in the corrosion resistance observed for the pure metal constituents, i.e., copper and nickel as a function of chloride concentration. The kinetic parameters of pitting corrosion of Cu–xNi alloys reflect the specific properties of both elements and suggest that an increase in Ni content above 40% would not have a significant effect on the corrosion resistance of Cu–xNi alloys.     

3-Mercaptopropyltrimethoxysilane as a Cu corrosion inhibitor in KCl solution

3-mercaptopropyltrimethoxysilane (MPS) has been used as a copper corrosion inhibitor in 0.100 mol L^–1 KCl solution. The inhibition was studied as a function of the MPS pretreatment concentration in ethanol. The MPS concentration used was between 1.0 × 10^–8 mol L^–1 and 1.0 × 10^–1 mol L^–1. A freshly-cleaned Cu electrode was inserted in an ethanolic solution of MPS for 30 min for pretreatment, and was then exposed to a 0.100 mol L^–1 KCl aqueous solution for 1 h. From the polarization resistance, the inhibition efficiency improved with increase in MPS concentration during the pretreatment. The MPS adsorption on Cu followed a Langmuir adsorption behaviour. However, at MPS concentrations larger than 1.0 × 10^–4 mol L^–1 the inhibition decreased. Moreover, the inhibition efficiency decreased with increase in the exposure time of the MPS modified Cu electrode in the KCl aqueous solution. Polarization studies suggest that MPS is an anodic as well as a cathodic inhibitor, in the presence of dissolved oxygen. X-ray photoelectron spectroscopy (XPS) analysis of the Cu samples showed that the organic compound modifies the Cu surface and scanning electron microscopy (SEM) studies indicated that MPS protects the Cu surface when exposed for 350 h to laboratory environment. Polarized grazing angle Fourier transform-infrared (FTIR) microscopy analysis determined the presence of a polymer on the Cu surface.     

Selection of an oxidant for copper chemical mechanical polishing: Copper-iodate system

Diagnostic criteria were developed to elucidate the reduction mechanism of an oxidant on a copper (Cu) surface at the corrosion potential. The corrosion potential of Cu tu was measured for various pH and iodate (IO₃^–) concentrations using the rotating disk electrode technique. According to the measured corrosion potentials, IO₃^– was an effective CMP oxidant only below pH Application of the diagnostic criteria on the Cu – IO₃^– system showed that the reduction of IO₃^– on Cu was under the mixed kinetic and diffusion control at the corrosion potentia l below pH 3. Above pH 3, however, the anodic process dominated over the cathodic process.     

Electrochemical and surface analysis study of copper corrosion protection by 1-propanethiol and propyltrimethoxysilane: A comparison with 3-mercaptopropyltrimethoxysilane

The inhibition of Cu corrosion by 1-propanethiol (1-PT) and propyltrimethoxysilane (PTS) molecules, in 0.100 mol L^–1 KCl solution, was investigated and compared to 3-mercaptopropyltrimethoxysilane (MPS). Corrosion inhibition was studied as a function of the 1-PT and PTS concentration in ethanol, between 1.0 × 10^–7 mol L^–1 and 1.0 × 10^–2 mol L^–1. Inhibition efficiency was calculated from Tafel plots in 0.100 mol L^–1 KCl solution. It improved with an increase in 1-PT or PTS concentration. The maximum efficiency was obtained at a 1-PT or PTS concentration of 1.0 × 10^–3 mol L^–1 or 1.0 × 10^–5 mol L^–1, respectively. Adsorption of 1-PT and PTS on copper followed a Langmuir behaviour. Potentiostatic polarization measurements indicated that 1-PT and PTS are mixed anodic/cathodic inhibitors, in the presence of dissolved oxygen. When the inhibitor exposure time of the pretreated Cu surface in 0.100 mol L^–1 KCl solution was varied, a loss on the corrosion inhibition efficiency was observed for the three (MPS, PTS and 1-PT) compounds. However, the 1-PT compound maintained excellent protection in the first 12 h of exposure to a 0.100 mol L^–1 KCl solution; afterwards, there was a significant loss in the inhibition efficiency. Surface analysis studies with Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) showed that the inhibitors modified the Cu surface.     

Inhibition of copper corrosion by several Schiff bases in aerated halide solutions

The inhibitive action of three Schiff bases, N,N -o-phenylen-bis(3-methoxysalicylidenimine) (V–o-Ph–V), N,N -p-phenylen-bis (3-methoxysalicylidenimine) (V–p-Ph–V) and N-[(2-hydroxy-3-methoxyphenyl)methylene]-histidine (V-His), on copper corrosion in aerated 0.5 mol dm^–3 NaCl and NaBr solutions was investigated using EIS and steady-state polarization techniques. The inhibitor effectiveness depended strongly on the geometric structure of the Schiff bases. Among the three kinds of Schiff base used, the inhibition efficiency of V–o-Ph–V on copper corrosion was the highest, V–p-Ph–V the next and V-His the lowest. The Schiff bases inhibited the cathodic current more significantly than the anodic current. The different influences of V–o-Ph–V or V–p-Ph–V on the anodic and cathodic reactions led to the appearance of a low frequency capacitive loop in the impedance spectra. The inhibition action of the Schiff bases was due to their adsorption on the copper surface followed by complexation with Cu(I) or Cu(II) ions, forming a blocking barrier to copper corrosion.     

Influence of 8-aminoquinoline on the corrosion behaviour of copper in 0.1 M NaCl

The corrosion behaviour of copper in aerated 0.1 M NaCl solution in presence of 8-aminoquinoline (8-AQ), using open circuit potential (OCP) measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) measurements and atomic force microscopy (AFM), was studied. The measurements revealed that the effect of 8-AQ is dependent on its concentration. For concentrations up to 10⁻³ M, the organic compound displaces the corrosion potential following no trend and also reduces the anodic current. In contrast, for concentrations higher than 10⁻³, 8-AQ reduces markedly both, the anodic and cathodic currents and consequently, the corrosion current density of copper. After 9 days of exposure in chloride solution, containing the organic compound, potentiodynamic polarization analyses showed a significant reduction in the anodic response and a less significant reduction in the cathodic response, which is associated with a film formed at the copper surface of about 10 μm in thickness and visually observed by a colour change of the copper surface.In order to elucidate the most likely interaction between the 8-AQ molecule and the different molecular structures probably present on copper surfaces in chloride solutions, some results obtained from theoretical calculations are presented. The following molecular structures were considered: CuCl molecule, CuCl₂⁻ complex, and little copper clusters defect representation built as five atoms on C_4v symmetry. Thus, based on the geometric, energetic, frontier orbital, and Total Electronic Density analysis done for the optimized states found for the systems investigated, we suggest that the most probable interaction of 8-AQ proceeds above CuCl units and free copper sites.     

Dodigen 213-N as corrosion inhibitor for ASTM 1010 mild steel in 10% HCL

This article describes a study of the behavior of a mixture of amines and amides, commercially known as Dodigen 213-N (D-213 N), as a corrosion inhibitor for ASTM 1010 mild steel in 10% w/w HCl solution. The concentration range used was 1 × 10⁻⁵ M to 8 × 10⁻⁴ M. The weight loss and electrochemical techniques used were corrosion potential measurement, anodic and cathodic polarization curves, and electrochemical impedance spectroscopy (EIS). The solution temperature was 50 ± 1 °C and it was naturally aerated. The corrosion potential values shifted to slightly more positive values, thus indicating mixed inhibitor behavior. The anodic and cathodic polarization curves showed that D-213 N is an effective corrosion inhibitor, since both the anodic and the cathodic reactions were polarized in comparison with those obtained without inhibitor. For all concentrations the cathodic polarization curves were more polarized than the anodic ones. The inhibition efficiency was in the range 75–98%, calculated from values of weight loss and corrosion current density, i _corr, obtained by extrapolation of Tafel cathodic linear region.     

Synergistic inhibition between 1-octadecanethiol and iodide ions on X60 pipeline steel for corrosion protection

The corrosion protection of carbon steel in 1?M HCl by 1-octadecanethiol (ODT) alone and in combination with iodide ions was investigated at ambient temperature using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. Results obtained showed that ODT alone offered low corrosion protection ability at very low concentrations. However, on addition of iodide ions, the corrosion protection potential was enhanced due to synergistic effect. Potentiodynamic polarization data revealed that ODT acts as mixed-type inhibitor influencing both the cathodic hydrogen evolution and anodic metal dissolution reactions. Adsorption of ODT onto the carbon steel surface followed Langmuir adsorption isotherm model. The existence of synergism phenomenon between ODT and iodide ions was confirmed from synergism parameter, which was found to be greater than unity. Quantum chemical calculations provide greater insight into the mechanism of electron transfer and mechanistic aspects of ODT on steel surface.     

Anodic oxidation of copper cyanide on graphite anodes in alkaline solution

The anodic oxidation of copper cyanide has been studied using a graphite rotating disc with reference to cyanide concentration (0.05–4.00 M), CN:Cu mole ratio (3–12), temperature (25–60 °C) and hydroxide concentration (0.01–0.25 M). Copper had a significant catalytic effect on cyanide oxidation. In the low polarization region (about 0.4 V vs SCE or less), cuprous cyanide is oxidized to cupric cyanide complexes which further react to form cyanate. At a CN:Cu ratio of 3 and [OH^–] = 0.25 M, the Tafel slope was about 0.12 V decade^–1. Cu(CN)₃ ^2– was discharged on the electrode and the reaction order with respect to the predicted concentration of Cu(CN)₃ ^2– is one. With increasing CN:Cu mole ratio and decreasing pH, the dominant discharged species shifted to Cu(CN)₄ ^3–. Under these conditions, two Tafel slopes were observed with the first one being 0.060 V decade^–1 and the second one 0.17–0.20 V decade^–1. In the high polarization region (about 0.4 V vs SCE or more), cuprous cyanide complexes were oxidized to copper oxide and cyanate. Possible reaction mechanism was discussed.     

Some phthalazin derivatives as non toxic corrosion inhibitors for copper in sulphuric acid

Phthalazin derivatives were tested as corrosion inhibitors of copper in 1 M H₂SO₄ using electrochemical polarization and weight loss techniques. This study monitored the evolution of the inhibitory effect of the phthalazin derivatives, according to their substituents. A significant decrease in the corrosion rate of copper was observed in the presence of the investigated inhibitors. The inhibition efficiency (%I) increases with increasing inhibitor concentration. The potentiodynamic polarization data indicated that, the inhibitors were of mixed type, but the cathodic effect is more pronounced. The slopes of the cathodic and anodic Tafel lines are approximately constant and independent on the inhibitor concentration. The mechanism of inhibition was discussed in the light of the chemical structure of the undertaken inhibitors. The adsorption on the copper surface follows the Langmuir isotherm model.     

Electropolymerization of 2-hydroxybenzothiazole (2-OHBT) in water–methanol media: electrochemical behaviour in NaCl (3%) solution

A new insulating thin polymer (<0.1m) formed by the electropolymerization of 2-OHBT is reported. The anodic oxidation of 2-OHBT on copper, iron and platinum in alcohol and alcohol–water solutions are investigated using cyclic polarization and chronoamperometry. Scanning electronic microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) are performed to confirm the presence of the organic layer. Based on the results obtained, a model for the formation mechanism is proposed. The corrosion behaviour of the coated copper is studied in NaCl (3%) solution by impedance spectrometry and anodic polarization. The results of these experiments show a decrease in the dissolution of copper due to the barrier properties of the organic coating.     

Passivation and pitting corrosion of tin in gluconate solutions and the effect of halide ions

The passivation and pitting corrosion of tin in sodium gluconate (SG) solutions was studied by using potentiodynamic and cyclic voltammetric techniques. Some samples were examined by X-ray and SEM. The effect of the concentration of gluconate ion, pH, potential scanning rate, successive cyclic voltammetry, switching potential and progressive additions of halide ions on the passivation and pitting corrosion of a tin anode was discussed. The data obtained show that low concentrations of SG have an inhibition effect on the pitting corrosion of tin in neutral media. The pitting corrosion of tin increases with increasing SG concentrations due to the formation of soluble tin-gluconate complex. The critical pitting potential depends on the gluconate ion concentration, pH and scan rate. Two cathodic peaks are observed in the cathodic polarization curve, corresponding to the reduction of the dissolved pitting corrosion products. The critical pitting potential shifts progressively to more negative values with increasing halide ion concentration. In all experiments, the aggressive action of halides decreased in the order Cl^–>Br^–>I^–.     

A near-infrared FT-Raman (SERS) and electrochemical study of the synergistic effect of 1-[(1′,2′-dicarboxy)ethyl]-benzotriazole and KI on the dissolution of copper in aerated sulfuric acid

The adsorption on copper in aerated 0.5 m sulphuric acid (30°C) of 1-[(1,2-dicarboxy)ethyl]-benzotriazole (BTM) has been investigated by means of surface enhanced Raman scattering (SERS) techniques. The inhibition efficiency in aerated acid increased with increasing BTM concentration to a maximum (52%) at the 1 × 10–3 m level. Benzotriazole (BTAH) was found to be about 20% more efficient as an inhibitor for copper corrosion under the same conditions. BTM (1 × 10–3 m) showed increased inhibition with increasing pH reaching a maximum value of 78.3% at pH 8. Polarization studies showed that BTM suppressed both the cathodic and anodic corrosion reactions. The SERS studies suggest that, like BTAH, BTM inhibits copper corrosion by adsorption through the azole nitrogen. This study also showed that the performance of BTM can be significantly improved by adding KI. SERS indicates that the iodide ions displace the protonated BTM on the copper surface and this is followed by an overlayer of protonated BTM molecules.     

Zn and Zn–Sn alloy coatings with and without chromate layers. Part I: Corrosion resistance and structural analysis

The aqueous corrosion resistances of Zn and Zn–Sn ( 20 wt% Sn) electrodeposits, passivated by immersion in chromating solution with different ratios of Cr(vi) to activating ions, are compared. The electrochemical behaviour of various chromated and nonchromated coatings were investigated in deaerated 0.5 mol dm^–3 Na₂SO₄/pH 5 solution using a.c. impedance and d.c. polarization techniques. The polarization curves revealed that the chromate layers influence both the cathodic and anodic reactions. The corrosion rate of each specimen decreases with time due to the accumulation of corrosion products. The dark yellow (DY) chromate film on the Zn–Sn alloy and the iridiscent yellow (IY) on Zn yields the best protective ability in agreement with the assessment of prolonged salt spray chamber tests. These chromate layers resembling cracked mud become permeable to the electrolyte after immersion and, as a consequence of the transformation and the leaching of certain Cr compounds, a very porous agglomerate of corrosion products forms. The morphology and structure of dark yellow chromated Zn–Sn alloy was also investigated by transmission electromicroscopy (TEM) and scanning electronmicroscopy with microprobe (SEM/EDS) analyses before and after corrosion. The depth profile of the corroded surface chemical composition was determined by X-ray photoelectron spectroscopy (XPS).     

Synthesis, Surface Properties, Synergism Parameter and Inhibitive Performance of Novel Cationic Gemini Surfactant on Carbon Steel Corrosion in 1 M HCl Solution

Electrochemical and gravimetric measurements were performed to investigate the effectiveness of a synthesized cationic gemini surfactant as corrosion inhibitor for carbon steel in 1 M HCl solution. The inhibition efficiency obtained from all methods are in good agreement. Potentiodynamic polarization measurements showed that, the prepared surfactant hinders both anodic and cathodic processes, i.e. acted as mixed-type inhibitor. It was found that the adsorption of the synthesized inhibitor followed the Langmuir adsorption isotherm and showed a mixed physical and chemical adsorption. Kinetic parameters were calculated and discussed. The inhibitor exhibited a synergistic effect with Sn²⁺ more than with Cu²⁺. The synthesized cationic gemini surfactant exhibited good surface properties.     

Corrosion of stainless steel (AISI 316) in molten sodium polysulphide under applied potential

The corrosion of AISI 316 steel has been investigated in sodium polysulphide melts in the region between 300 and 410°C which is of interest with respect to the Na/S battery. Although AISI 316 is not suitable as a corrosion-resistant casing material, it can serve as a model material for the elucidation of basic mechanisms. Both anodic and cathodic potentials were applied in order to represent the conditions in a cell. The corrosion products formed multilayer scales, the inner one consisting primarily of chromium sulphide which acted as a corrosion barrier. The corrosion reaction had an activation energy of 105 kJ mol^–1. In the higher temperature region the scale dissolved partially in the melt due to a change in the scale morphology. Possible mechanisms for anodic and cathodic corrosion reactions are discussed.     

Anodic behaviour of alkaline solutions containing copper cyanide and sulfite on the graphite anode

Sulfite may be added to copper cyanide solutions to reduce cyanide oxidation at the anode during copper electrowinning. Anodic sulfite oxidation is enhanced in the presence of copper cyanide. Sulfite also suppresses the oxidation of copper cyanide. The effect of sulfite on the oxidation of copper cyanide decreases with increasing mole ratio of cyanide to copper. This is related to the shift in the discharged species from Cu(CN)₃ ^2– to Cu(CN)₄ ^3– with increasing mole ratio of cyanide to copper. Sulfite is oxidized to sulfate. At [Cu⁺] = around 1 M, CN:Cu = 3.0–3.2, [OH^–] = 0.05–0.25 M, [SO₃ ^2–] = 0.4–0.6 M and the temperature = 50–60 °C, the anodic current efficiency of sulfite reached 80–90%. With further increase in sulfite concentration beyond 0.6 M, the current efficiency of sulfite oxidation will not be increased significantly. Further increase in CN:Cu mole ratio will result in decrease in the anodic current efficiency.     

Electrodissolution kinetics of an Fe−Ni alloy in acidic chloride media of 1.0 M ionic strength

Anodic dissolution of an Fe–5Ni alloy in deoxygenated acidic chloride solutions of 1.0 M ionic strength has been studied. Steady state partial current densities of the iron and nickel components were obtained by atomic absorption spectrophotometry analysis of the solutions. Alloy and component electrodissolution rates show two anodic Tafel regions indicating simultaneous parallel reactions as reported previously for pure iron. Anodic Tafel slopes of 0.075 and 0.04V dec^–1 were obtained in the lower (A) and higher (B) polarization regions, respectively. The kinetic results for the alloy are consistent with the Cl^– accelerated mechanism in Region (A) and the Bockris or OH^– accelerated mechanism in Region (B) for both iron and nickel components as proposed previously for pure iron.     

Electrochemical behaviour of iron and copper in a culture solution for Spirulina platensis

Cyclic voltammograms of iron and copper electrodes were run in sodium hydroxide, carbonate–bicarbonate buffer and culture media for Spirulina platensis at 30°C. Potentiostatic steady state polarisation curves for both electrode surfaces in these electrolytes were performed in the presence and the absence of S. platensis at fixed temperature. Corrosion potential and corrosion current density values of iron and copper were obtained graphically from these curves. In all cases, the largest corrosion current density corresponded to the maximum biogenerated-oxygen concentrations, that is, illuminated culture media containing S. platensis. Corrosion potentials of iron electrodes shifted to positive values for increasing corrosion rates, whereas constant corrosion potentials were obtained for copper electrodes independently of the electrolyte.