The effect of magnesium additions on the microstructure and cut edge corrosion resistance of zinc aluminium alloy galvanised steel

The magnesium levels in 20 μm thick 4.5% Al/Zn galvanising coatings applied to 0.7 mm gauge steel under continuous galvanising conditions were altered from 0.0% to 0.05%. The additions result in an increase in the zinc dendrites (volume fraction from 6% to 22% and number from 150 to 325 mm⁻²) since magnesium depresses the eutectic temperature increasing the freezing range. The microstructural modification results in increasing cut edge corrosion determined using a scanning vibrating electrode technique for 24 h exposure to 5% NaCl. The Mg additions result in an increase in zinc loss (from 80 to 185 μg), an increase in active anode numbers (from 600 to 1700 m⁻¹ cut edge) and an increase in the number of long lived anodes.     

The effect of pyrrole-halide mixtures in inhibiting the dissolution of low-carbon steel in sulphuric acid

A rapid-polarization technique was used to study the mechanism by which the pyrrolehalide inhibitor system affects the corrosion of low-carbon steel in a 2N sulphuric acid solution. Pyrrole primarily inhibits the cathodic reaction, whereas the halides seem to strongly inhibit the anodic reaction. Weight-loss measurements indicated that the corrosion rate of steel rapidly increases with temperature over the range 100–200°F (38–93°C) both in the presence and absence of inhibitors, with an apparent activation energy in all instances of 12.6 kcal/mole.     

Ethoxylated fatty alcohols as corrosion inhibitors for dissolution of zinc in hydrochloric acid

The effect of some ethoxylated fatty alcohols, with different numbers of ethylene oxide units, on the corrosion of zinc in 0.5 M HCl has been studied using weight loss and polarization measurements. The inhibition efficiency was found to increase with increasing concentration, number of ethylene oxide units per molecule and with decreasing the temperature. Inhibition was explained on the basis of adsorption of ethoxylated fatty alcohols molecules on the metal surface through their ethoxy groups. The degree of surface coverage varied linearly with logarithm of inhibitor concentration fitting Temkin isotherm. The thermodynamic parameters were calculated for the tested system from the data obtained at different temperatures.     

The effect of alloying additions on the superplasticity of biphase brass

Conclusion The use of small additions ensuring smaller grain size and slower grain growth, improving the equiaxiality of the grains and reducing diffusional porosity while maintaining equality of volumes of - and -phases makes it possible to control the indices of superplasticity of brasses.MISiS. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 11–19, November, 1986.     

Effect of mechanical activation on dissolution kinetics of neutral leach residue of zinc calcine in sulphuric acid

Neutral leach residue of zinc calcine (NLRZC) was mechanically activated by a stirring ball mill. Subsequently, the changes in physicochemical properties and dissolution kinetics in sulphuric acid were studied. The crystalline structure, morphology, particle size and specific surface area of the non-activated and mechanically activated NLRZC were characterized by X-ray diffraction, scanning electron microscope, particle size analyzer and volumetric adsorption analyzer, respectively. The characterization results indicate that mechanical activation (MA) induced remarkable changes in the physicochemical properties of NLRZC. The leaching experiments show that MA significantly enhances the leaching reactivity of NLRZC using the zinc extraction as evaluating index. After NLRZC is mechanically activated for 30 min and 60 min, the activation energy decreases from 56.6 kJ/mol of non-activated NLRZC to 36.1 kJ/mol and 29.9 kJ/mol, respectively. The reaction orders of the non-activated, 30 and 60 min activated NLRZC dissolution with respect to H₂SO₄ concentration were found to be 0.34, 0.30, and 0.29, respectively.     

The effect of dicarboxylates on the anodic dissolution of cobalt

The effect of sodium salts of dicarboxylic acids on the anodic dissolution of cobalt in solutions of perchlorates is considered. Acceleration of the dissolution is observed only if the pH of such a solution falls into the domain of the formation and existence of soluble complexes of Co(II) with the corresponding acid. The mechanism of the anodic dissolution of cobalt in the presence of dicarboxylates is suggested.     

Inhibition effect of some surface active agents on dissolution of copper in nitric acid

Abstract

The inhibitive efficiency of some nonionic, amphoteric, cationic, and anionic surface active agents (surfactants) on the dissolution of copper in 4·5M HNO₃ was studied at 25°C by the weight loss method. The percentage inhibition I increases as the concentration of the cationic, nonionic, and amphoteric substances increases and reaches a limiting value. It is suggested that this is due to the formation of a monolayer on the surface of the metal; the Langmuir adsorption isotherm was confirmed. In the case of anionic surface agents, the percentage inhibition values were at their highest at low surfactant concentrations and decreased as the concentration of the surfactant increased.     

Effect of additions of zinc stearate on the properties of sintered Nd-Fe-B magnets

Zinc stearate additions have been used to increase the remanence of sintered Nd-Fe-B magnets produced by the powder metallurgy without powder pressing. Zinc stearate acts as an internal lubricant, i.e., it decreases the friction forces between the particles and favors an increase in the degree of texture of the powders, which is induced by the magnetic field. It is shown that the density and the magnetic hysteresis characteristics of sintered magnets produced using additions of 0.15 wt % zinc stearate exceeds the corresponding values obtained for magnets produced without this addition at a filling density of powders in containers of more than 2.9 and 3.0 g/cm³ in dry and wet states, respectively. Using additions of zinc stearate in the amount of 0.15% with respect to the weight of the powder, magnets with a density of 7.55 g/cm³, B _r = 14.02 kG, H _c = 7.91 kOe, and (BH)_max = 46.1 MG Oe have been produced.     

Effect of alloying additions on the structure and corrosion properties of zinc coatings

Conclusions Prolonged corrosion tests in a stream of sea water on samples galvanized in baths with different alloying additions showed that the corrosion resistance of zinc coatings in sea water can be improved by alloying with 0.01% Ti+0.05% Mg+0.1% Al and with 0.01% Ti.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 45–47, May, 1974.     

The effect of additives on zinc deposited from zinc sulfate solutions

Zinc is industrially electrowon from acid zinc sulfate solutions at ambient temperatures. Some refining agents are usually added to improve the deposit qualities. Gelatin is a traditional additive, but other additives are also used. In the investigation described here, the basic parameters of deposition (e.g., current density, acid concentration, and zinc concentration) were optimized. Gelatin and a tetraalkylammonium salt (TAS) were used separately and in combination as grain refiners of the cathodic deposits. Current efficiency determination experiments were performed to investigate the role of these additives. Scanning electron micrographs of the cathodic deposits were obtained to examine the surface qualities of deposits at certain conditions. Results showed that gelatin is generally a better refiner, although TAS may be used in concentrations of 0.074 mg/l to 1 mg/l. A mixture of the two additives resulted in a decrease of current efficiency.     

Inhibition of zinc dissolution in borate-sulfate electrolytes by benzoimidazoles

The effects of the concentrations of sodium sulfate, benzoimidazole, and its derivatives on active and passive zinc dissolution and local depassivation were studied. The correlations between the effect of substituted benzoimidazoles and the basicity, polarizability, and hydrophobicity were determined. Original Russian Text ? V.V. Ekilik, V.V. Chernyavina, G.N. Ekilik, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 3, pp. 262–267.     

The kinetics of the anodic dissolution of copper in acid chloride solutions

The anodic dissolution of copper has been studied in different acid chloride solutions under potentiostatic conditions. A rotating disk electrode technique was employed.The results showed that the slow cuprous chloride complexes transferred towards the bulk is the r.d.s. all over the polarization range. Anodic limiting currents have been also observed and explained.     

The effect of anions on the anodic dissolution of nickel silicide in sulfate electrolytes

Anodic dissolution of nickel and nickel silicide in a 0.5 M H₂SO₄ solution in the presence of halide and thiocyanate ions is studied with the use of cyclic voltammetry. Main regularities of the effect of anions on the mechanism and kinetics of the anodic dissolution of the metal and its silicide are found. The results obtained reveal different nature of the passivation processes and different compositions of the oxide films formed on Ni and NiSi. Original Russian Text ? A.B. Shein, O.S. Ivanova, R.N. Minkh, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 1, pp. 38–44.     

The effect of some B-diketo compounds on the retardation of aluminium dissolution in HCl

The inhibitive action of some B-diketo compounds on the dissolution of aluminium in 2M HCl has been investigated by hydrogen evolution, thermometric and weight loss techniques. The adsorbability of inhibitors is dependent on the basicity of the oxygen and nitrogen sites involved. The dissolution reaction of aluminium in hydrochloric acid solutions is zero order and remains so when B-diketo compounds are present. The rate constant decreases as the inhibition efficiency increases. The activation energy of the dissolution reaction increases with decreasing acid concentration and increasing inhibitor concentration. Values of the Arrhenius activation energies agree with those obtained for an activation controlled process.     

The effect of solid solution W additions on the mechanical properties of nanocrystalline Ni

Although pure metals with grain sizes below about 10 nm are very difficult to prepare, alloying enables the realization of finer grain sizes, often down to the amorphous limit. In this work, the role of solid solution additions of ~13 at% W are considered with respect to the structure and mechanical properties of electrodeposited Ni alloys with grain sizes below 10 nm. Structure of the nanocrystalline alloys is analyzed by high-resolution transmission electron microscopy, and related to the mechanical properties assessed by instrumented nanoindentation and nano-scratch experiments. The Ni-W alloys exhibit higher hardness and scratch resistance as compared to the finest pure nanocrystalline Ni alloys, although the contribution of solid solution strengthening from W is expected to be essentially negligible. The improved properties are therefore most likely due to the finer length scale available in multicomponent nanocrystalline alloys, and suggest that alloying may suppress the breakdown of Hall-Petch strengthening to finer grain sizes. Finally, the present data are shown to smoothly bridge the hardness-grain size trend between nanocrystalline Ni (grain size>10 nm) and amorphous Ni-based alloys.     

The dissolution of silver cathodically polarized in acid chloride media

The dissolution of silver cathodically polarized in a 1M HC1 solution is investigated. It occurs only in the presence of oxygen, is independent of the cathodic potential in a range from 0.00 to −0.45 V, and is determined by the convective experimental conditions and the acidity of the solution. It may be assumed that silver can be oxidized at cathodic potentials because of an increase in the concentration of hydroxide ions adsorbed by the electrode, during the reduction of the dissolved oxygen. Original Russian Text ? L.E. Volkova, I.K. Marshakov, N.M. Tutukina, I.V. Kreiser, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 2, pp. 154–157.     

The effect of sorbed hydrogen on the kinetics of active dissolution of iron

The effect of hydrogen adsorbed or absorbed by iron (0.009% C) on the iron dissolution is studied on a bipolar electrode-membrane in 0.5 M SO ₄ ²⁻ solutions (pH 1.30) by cyclic potential pulses. Expressions that allow one to calculate the hydrogen coverage on the iron surface (θ) as a function of the potential variation in a cyclic stepwise manner and also the hydrogen concentration in the near-surface metal layer (C) as a function of variations in the intensity of the diffusion flow of hydrogen atoms in the membrane are given. The method of cyclic potential pulses together with the analysis of solutions for metal ions shows that the iron dissolution rate substantially decreases as θ increases. A bipolar electrode-membrane allowed the determination of the C intervals corresponding to the inhibition of iron dissolution (at C < C _c ≈ 3 × 10⁻⁸ g-at/cm³), the activating effect of hydrogen absorbed by the metal on the anodic process (for C > C _c), and the metal destruction (for C ≫ C _c). The absorbed hydrogen is assumed to accelerate the ionization of iron due to the formation of new dissolution sites as a result of plastic deformations of the metal. Thus, the effects of two forms of sorbed hydrogen on the iron dissolution are separated. Original Russian Text ? A.I. Marshakov, A.A. Rybkina, T.A. Nenasheva, 2007, published in Korroiya: Materialy, Zashchita, 2006, No. 5, pp. 2–14.