The effect of additives on the corrosion resistance of Zn electrode in alkaline battery system

Zn electrodes are widely used as an anode material in alkaline battery systems in highly concentrated KOH electrolyte. However, it is well known that their life cycle is significantly shortened due to dendrite growth caused by high dissolution and rapid electrochemical reaction. In this study, additives such as Ca(OH)_￡σ, citrate, tartrate, and gluconate were added to 40% KOH electrolyte solution at 25 and 5 wt.% Pb₃O₄ was mixed with the Zn electrode. The effects of both Pb₃O₄ and the additives on the electrochemical behavior of the Zn electrode were investigated through corrosion potential measurements, potentiodynamic polarization curves, cyclic voltammetry, and SEM photographs. The addition of Pb₃O₄ had a considerable effect on decreasing the corrosion rate of the Zn electrode, and the corrosion potential of the Zn electrode with Pb₃O₄ addition shifted to a more positive potential than that of a pure Zn electrode. However, upon addition of other additives, the corrosion potential was slightly shifted to the negative direction again. The addition of 4 kinds of additives appeared to play an important role in improving the corrosion resistance. Moreover, among the four additives, tartrate displayed a relatively good effect in terms of increasing the corrosion resistance as well as improving the discharging characteristics among.     

碱溶液中添加剂对铝阳极行为的影响

为了提高铝活化性能以及降低析氢腐蚀,用电化学方法研究了在4mol／LKOH溶液中,添加剂酒石酸钾钠（C4H4O6KNa）、邻氨基苯酚（NH2C6H4OH）以及复合添加剂对铝阳极（W（AJ）=99．999％）电化学行为的影响。结果表明：C4H4O6KNa对抑制铝的析氢腐蚀作用不大,但大幅度提高铝阳极的活性。添加NH：C6H40H,主要作用是大幅度抑制铝的析氢腐蚀,对铝活性几乎无影响。复合添加剂（C4H4O6KNa＋NH2C6H4OH＋KMnO4）能明显降低铝阳极在碱性介质中的极化,提高其活性,同时析氢腐蚀也降低,其最佳配方为：15mmol/L C4H4O6KNa＋0．4mol／LNH2C6H4OH＋0．8mmol／LK2MnO4。     

Effects of additives on zinc electrodeposition from alkaline zincate solution

The effects of additives on the surface and cross-sectional morphologies of zinc deposits on iron substrate from alkaline zincate solution were characterized by scanning electron microscope (SEM). The cathodic reaction mechanisms under various concentrations of additives were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. It is found that with increasing the additive A content in the bath solution, the nucleation overpotential (NOP) value is obviously increased and the inhibition effect is strengthened. This may be mainly due to the adsorption of additive A on the cathodic electrode surface, which can cover the active sites and block the discharge reduction. The results of EIS analysis indicate that the rate-determining step of zinc electrodeposition process is changed from mixed control step into electrochemical reduction step in the presence of additive A. However, any quantity of additive B has little effect on the NOP value and the inhibition effect is not obvious. Furthermore, addition of additive A and additive B at the same time displays the strongest inhibition effect and shows a strong synergism because of their co-adsorption on the cathodic electrode surface.     

The effect of phosphorus-containing additives in fuels on automobile exhaust valve corrosion

It is suggested that the burning of exhaust valves involves the participation of sodium sulphate, arising from salt ingested with the air and sulphur in the fuel. Phosphate salts, such as lead phosphate which arises from lead anti-knock additives and phosphorus ignition control additives, may increase this accelerated attack. To test the roles of the various possible salt species the effect of mixtures of sodium sulphate and lead phosphate, sodium sulphate and sodium phosphate, lead sulphate and lead phosphate, and sodium sulphate and phosphorus pentoxide on the corrosion of a stainless steel, Fe-18% Cr, the cobalt-base alloy X-40 and the nickel-base alloy Nimonic 115 in a crucible test have been studied.The results show that the presence of sulphates markedly enhances corrosion, with internal sulphides being formed: in alloys containing nickel a liquid sulphide can be formed resulting in accelerated attack. The presence of phosphorus enhances the attack of sodium sulphate: for these alloys pure sodium sulphate is not particularly aggressive, but the addition of phosphate salts resulted in heavy corrosion.Phosphorus-rich mixtures appeared to be capable of producing a type of corrosion involving direct participation of phosphorus, forming phosphides or phosphates of the metals.The presence of sodium is not essential for heavy attack. Lead sulphate-lead phosphate mixtures produced heavy corrosion of all the alloys studied.     

The effect of fluoride on corrosion of reinforcing steel in alkaline solutions

The influence of fluoride content of alkaline solutions on the corrosion of reinforcements has been studied, by means of electrochemical techniques, in saturated solutions of Ca(OH)₂ and same pH NaOH solutions with additions of NaF, thus simulating the liquid phase of concrete. Fluoride can be present as a minor component in low-energy cements. The joint presence of chlorides and fluorides in the corrosion process of steel has also been analysed. It has been established that fluoride anions are able to produce pitting of reinforced steel in alkaline media of high pH. In Ca(OH)₂ saturated solution, the precipitation of CaF₂ lowers F⁻ concentration below the minimum that promotes a pitting corrosion process; if there is not enough Ca(OH)₂ to precipitate all F⁻ ions, the presence of fluoride in these media causes an increase in passive film dissolution and corrosion rates.     

The effect of stress on the corrosion behaviour of mild steel in alkaline solutions

The influence of stress, type of aggressive anion and anodic current density on the corrosion behaviour of mild steel in lime water has been studied. Under open circuit condition the passivity of steel in lime water containing low concentrations of C1?, SO₄^2? or S^2? ions was impaired by the application of stress. In the presence of high concentrations of these ions corrosion was enhanced by the application of stress. Sulphide ions were found to be more dangerous than C1- or SO₄^2? ions at the free corrosion potential. With anodic polarization, S^2? ions are inhibitive both in the absence and in presence of stress. In early stages at low current densities, the anodic process was stimulated by the application of stress.     

Effect of tin on the corrosion behavior of low-alloy steel in an acid chloride solution

This study examined the effect of Sn addition ranging from 0 to 0.1 wt.% on the electrochemical properties of low-alloy steel using electrochemical techniques in an acid chloride solution and surface analysis techniques. The potentiodynamic test showed the active corrosion behavior of all specimens and the corrosion rate decreased with increasing Sn addition. EIS showed that the Sn-containing steels had higher rust layer resistance. These results confirmed that the interaction of Sn with Cu and Sb improves the corrosion resistance of low-alloy steel due to the formation of the continuous tin oxide, copper oxide and antimony oxide layer.     

The effects of Phyllanthus amarus extract on corrosion and kinetics of corrosion process of aluminum in alkaline solution

The effect of the extract of Phyllanthus amarus leaves on the corrosion of aluminum in 2 M NaOH solution was studied using chemical technique. The extract acts as corrosion inhibitor, with 76% efficiency at the highest concentration in the alkaline environment and the inhibition efficiency increased with increasing concentration of the extract. The adsorption of the inhibitor on aluminum surface was in accordance with the Langmuir adsorption isotherm. A zero-order kinetics relationship with respect to aluminum was obtained with and without the extract from the kinetics treatment of the data.     

Identification of steel corrosion in alkaline sulfate solution by electrochemical noise

Research on the effects of sulfate ions on steel corrosion has been conducted in response to the observations of premature localized corrosion of steel strands in cementitious grouts in posttensioned bridge construction. Electrochemical noise (EN) was shown to be an effective technique to assess the development of localized corrosion of steel in the alkaline sulfate solution. General statistics of the EN potential and current time signatures revealed the negative effect of elevated sulfate concentrations and the development of pitting events. Spectral analysis indicated an increase in the characteristic charge and decrease in characteristic frequency with sulfate ion concentration, whereas an increase in the overall corrosion rate was observed, indicating the development of pitting corrosion. Pitting events could be sustained in solutions above 10 g Na₂SO₄/L H₂O and more extensive localized corrosion developed above 20 g Na₂SO₄/L H₂O.     

The effect of some hydrazine derivatives on the corrosion of Al in HCl solution

The inhibitive effect on the corrosion of aluminium in hydrochloric acid of Girard's T and P, oxalic, malonic and succinic acid hydrazides and acetophenone G-T was studied by thermometric and weight loss measurements. Adsorption of these hydrazine derivatives leads to the formation of a monolayer of the adsorbate on the metal surface. The results indicate that all the studied compounds can be classified with the weakly adsorbed substances except acetophenone G-T which is strongly adsorbed.     

Inhibitive effect of sodium eperuate on zinc corrosion in alkaline solutions

The effect of sodium eperuate prepared from Wallaba (Eperua falcata Aubl) extract on zinc corrosion was investigated in alkaline solutions with chloride ions (i.e., simulated concrete pore solutions) by using electrochemical techniques. Sodium eperuate inhibits the corrosion of zinc in 0.1 M NaCl solutions with pH 9.6. As its concentration increases to 1 g/L, the inhibition efficiency reaches approximately 92%. In alkaline solutions with pH 12.6, sodium eperuate has no adverse effect on passivity of zinc, and retards the chloride attack. These suggest that sodium eperuate is an effective inhibitor for the protection of zinc in alkaline environments.     

添加剂硫脲对铝阳极电化学行为的影响

为了提高铝的耐蚀性以及活化性能,用线性扫描伏安法、交流阻抗、恒电流放电等方法,研究了在4 mol/L的KOH溶液中,添加剂硫脲对铝阳极(w(Al)=99.999%)电化学性能的影响,结果表明:当硫脲质量分数为3%时,铝阳极具有较好的活化和缓蚀性能.铝的缓蚀率达48.7%,且开路电位Eocp负移出现最大值达-1.74 V.在-1.2 V下,铝的电流密度高达122.6 mA/cm2,比在4 mol/L的KOH中要大102.5 mA/cm2.     

The effect of pretreatments with siloxanes on the corrosion resistance of aluminium in NaCl solution

The inhibitory action of different pretreatments with metacryloxypropylmethoxysilane (MAOS) on the corrosion of aluminium in NaCl aqueous 3.5% solutions has been examined.Free corrosion and electrochemical tests (potentiodynamic polarisation and electrochemical impedance spectroscopy) were performed to characterise the resistance to general and localised corrosion of pretreated specimens. The surfaces of uncorroded pretreated samples were characterised by SEM and AFM. Their surfaces were also examined with XPS technique before and after corrosion attack.It was found that the inhibitory action of MAOS against general and localised corrosion depends on the nature of the solvent in which it is dispersed. The siloxane polymeric film formed by MAOS aqueous dispersion acts as a good corrosion inhibitor in the whole exposure time range, whereas the inhibitory power of the polymeric film formed by MAOS methanol solutions decreases with increasing immersion time.     

Hydrogen generation using the corrosion of Al-Sn and Al-Si alloys in an alkaline solution

We investigated the effects of adding Sn and Si to Al alloys on the corrosion of the alloys and the generation of hydrogen from an alkaline solution using the alloys. With increasing Sn content of up to 20 wt% in the Al-Sn alloy, the volume fraction of the Sn phase as a cathodic site at grain boundaries increased, and consequently, the hydrogen generation rate from an alkaline solution by the alloy also increased. In addition, the quenched Al-Sn alloys had smaller grain sizes compared to the furnace-cooled alloys, and accordingly, exhibited a slightly higher hydrogen generation rate. A galvanic cell was formed between the Al grain and the Sn phase of the grain boundary, and accordingly, intergranular type corrosion was observed on the Al-Sn alloys. Compared with the Al-Sn alloys, a more uniform type corrosion was observed on the Al-Si alloys because the nobler Si was uniformly distributed in the eutectic region formed between the primary Al grains. The hydrogen generation rate increased with an increasing Si content up to 10 wt% and was greater for the furnace-cooled samples than that for the quenched samples due to the more clearly formed eutectic structure.     

Effects of grain size on the electrochemical corrosion behaviour of electrodeposited nanocrystalline Fe coatings in alkaline solution

Effect of grain size reduction on the electrochemical corrosion behaviour of nanocrystalline Fe was investigated using Tafel polarization curves and electrochemical impedance spectroscopy (EIS) measurements. Nanocrystalline iron was fabricated by pulse electrodeposition using citric acid bath. The grain size of a nanocrystalline surface was analyzed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The corrosion resistance of Fe in alkaline solution considerably increased as the grain size decreased from microcrystalline to nanocrystalline. The behaviour of passive film growth and corrosion was discussed in terms of excess of free energy caused by nanocrystalline surface.     

The inhibition effect of 2,4,6-tris (2-pyridyl)-1,3,5-triazine on corrosion of tin, indium and tin-indium alloys in hydrochloric acid solution

The influence of 2,4,6-tris (2-pyridyl)-1,3,5-triazine (TPTZ) on the corrosion of tin, indium and tin-indium alloys in 0.5 M HCl solution at different temperatures was studied. Potentiodynamic cathodic polarization and extrapolation of cathodic and anodic Tafel lines techniques were used to obtained experimental data. In the case of tin, the percent inhibition efficiency (IE%) increases as both concentration of TPTZ and temperature are increased. The value of activation energy (E_a) is smaller in the presence of TPTZ than that in uninhibited solution, and decreases with increasing the concentration. However, the effect of TPTZ on indium and the investigated alloys exhibited similar behavior; so, the maximum inhibition efficiency is observed at lowest concentration (10⁻⁶ M) of TPTZ. Then, the value of inhibition efficiency starts to decrease gradually with increasing TPTZ concentration than that of 10⁻⁶ M. But at higher concentration (10⁻³ M) the corrosion current density (I_corr) is still lower than that in uninhibited solution. SEM photographs support that the higher inhibition efficiency is observed at 10⁻⁶ M of TPTZ.The plots of ln K versus 1/T in the presence of the TPTZ in the case of tin, the inhibitor showed linear behavior. The standard enthalpy, ΔH°_ads., entropy, ΔS°_ads. and free energy changes of adsorption ΔG°_ads. were evaluated using Frumkin adsorption isotherm.     

The inhibition of the corrosion of iron in alkaline solutions

Abstract

The inhibition of the corrosion of iron in alkaline solutions is due to the anodic formation of a film of a ferrous compound, which is usually ferrous hydroxide, but in the presence of anions yielding less soluble ferrous salts, e.g. carbonate, the composition may be mixed. The ferrous compounds are subsequently oxidised to anhydrous cubic oxide; consequentty the film thickens until it prevents the passage of ferrous ions into solution.     

Investigation on the corrosion inhibitive effect of 2H-pyrazole-triazole derivatives in acidic solution

Four research methods, such as weight loss test, electrochemical techniques, adsorption isotherm, and quantum chemical calculation, were employed in this paper to study the inhibition efficiency (IE) and inhibition mechanism of three 2H-pyrazole-triazole derivatives, BHOT, FHOT, and CHOT in 1 M HCl solution for mild steel. Using the electrochemical technique, three inhibitors were proved to show a mixed-type character for mild steel by suppressing both anodic and cathodic reactions on the steel surface. The adsorption models of three compounds were established at different temperatures according to their adsorption isotherms. The results of the quantum chemical calculation method indicated that the adsorption sites of 2H-pyrazole-triazole derivatives were strongly centralized on benzene ring, triazole ring, or other substituents. All the results showed that the three derivatives were excellent inhibitors in 1 M HCl solution for mild steel.     

Initial corrosion protection of Zn–Mn alloys electrodeposited from alkaline solution

The effects of a deposition current density (c.d.) on the corrosion behaviour of Zn–Mn alloy coatings, deposited from alkaline pyrophosphate solution, were investigated by atomic absorption spectrophotometry (AAS), X-ray diffraction (XRD), atomic force microscopy (AFM), optical microscopy, electrochemical impedance spectroscopy (EIS) and measurement of corrosion potential (E_corr). XRD analysis disclosed that zinc hydroxide chloride was the main corrosion product on Zn–Mn coatings immersed in 0.5 mol dm⁻³ NaCl solution. EIS investigations revealed that less porous protective layer was produced on the alloy coating deposited at c.d. of 30 mA cm⁻² as compared to that deposited at 80 mA cm⁻².     

The synergistic effect of anions and the ammonium cation on the inhibition of iron corrosion in acid solution

The synergistic effect of various anions and the tetra-n-butylammonium cation on the inhibition of iron corrosion in 1 M HClO₄ and their joint adsorption on iron were studied by using an impedance and a polarization technique. Surface coverage obtained from double layer capacitance showed joint adsorption of the anion and cation on the iron surface. Assuming competitive adsorption of these ions at the interface, the synergism of corrosion inhibition and joint adsorption were estimated using a parameter calculated from the inhibition efficiencies and the surface coverages of the anion and/or cation. The synergistic effect was shown for all of the anions and cation examined.