An analytical procedure for determination of the Cd, Pb, Cu, Sb, Zn and Cr is described in Thorium compounds such as thorium oxide and thorium nitrate without prior matrix separation. Square wave voltammetry is employed using a HMDE/Ag-AgCl (3M KCl)/Pt-rod electrode system. Determination of the Cd, Pb, Cu and Sb is carried out simultaneously using 2M HCl as supporting electrolyte. For determination of Zn, 0.1 M HCl is used and for Cr a mixture of 0.01 M acetate buffer, 0.5M sodium nitrate and 0.04M Diethyl triamine pentaacetic acid (DTPA) (complexing agent) are used as supporting electrolyte. This method is suitable for determination of Cd, Pb, Cu, Sb, Zn and Cr as low as 0.05 mu g/g, 0.2 mu g/g, 0.3 mu g/g, 0.1 mu g/g, 0.2 mu g/g and 0.05 mu g/g respectively with a relative standard deviation of 10-12%.
This study includes the determination of stability constant of mixed ligand complexes of Pb(II) with some amino acids (DL-Glycine, DL-Alanine, L-Aspartic Acid and L-Glutamic Acid) and TDGA (Thiodiglycolic Acid) polarographically. For this purpose, extended methods of Schaap and McMasters have been used. The reduction in each case has been found to be diffusion controlled and reversible involving two electrons. Three types of mixed ligand complexes (MXY, MXY2 and MX2Y) have been formed. With the help of stability constants, statistical and electrostatic effects have been discussed.
The effect of the surfactant on the electro-reduction of the nitro moiety in beta nitrostyrene has been studied using anionic, cationic and non-ionic surfactants. In the case of cationic surfactant there was an enhancement of reduction current and decrease in peak potential with the increase in surfactant concentration. This is attributed to the interaction between the binder and the hydrophobic part of the surfactant. In the presence of non ionic surfactant, the cathodic potential shifts to more negative values making nitro group less vulnerable for reduction.
This paper deals with the high corrosion resistance developed by the metal matrix composites when compared with that of matrix alloy. Reinforcement selected is Silicon Carbide particulates, which is a ceramic material. The composite's are prepared using liquid melt metallurgy technique using vortex method. Matrix alloy is heated to liquidus temperature and a vortex is created using an impeller. Corrosion tests were conducted at room temperature (296K) using conventional weight loss method according to ASTM G69-80. The corrodents used for the tests were Equimolar solution of Sodium Hydroxide and sodium chloride solutions. Corrosion rates were also calculated. In each case the corrosion rate in hydrochloric acid and sodium chloride solutions decreases with increase in exposure time for matrix and metal matrix composites.
Corrosion of aluminium in different concentrations of HCl solution was studied by mass loss and thermometric method in absence and presence of the alcoholic extract of Prosopis cineraria (PC). From the mass loss data, it is concluded that the inhibition efficiency increased with the increase in concentration of inhibitor. The alcoholic extract of Prosopis cineraria is found to be effective corrosion inhibitor giving up to 96.93% efficiency and can be safely used without any toxic effects.
The inhibitory action of polyethylene glycol (PEG) on the corrosion of mild steel in H2SO4 was investigated using weight loss, hydrogen evolution and thermometric methods at 303-333K. The effect of halides namely: KCl, KBr and KI is also reported. It was found that PEG acted as an inhibitor for mild steel corrosion in acidic medium. Inhibition efficiency increases with increase in PEG concentration. Addition of halides also increases the inhibition efficiency to a considerable extent. An increase in temperature led to increase in the corrosion rate and inhibition efficiency in the absence and presence of inhibitors and halides. The inhibition efficiency (%I) and degree of surface coverage (0) increased in the order: KI > KBr > KCl, which indicates that the radii and the electro negativity of the halide ions play a significant role in the adsorption process. The values of the synergism parameter, S-I obtained are greater than unity, which suggest that the enhanced inhibition efficiency is only due to synergism. PEG obeys Freundlich, Langmuir and Temkin adsorption isotherms. Phenomenon of chemical adsorption is proposed and the thermodynamic parameters suggest that the adsorption process is spontaneous.
Corrosion problem in pulp and paper industry poses serious threats due to high cost involved in the replacement of materials and maintenance. Organic compounds are a reliable and a cost effective measure to deal with corrosion problems in the various corrosive sections of the paper industry. Few nitrogen and sulfur containing compounds were synthesized namely, 1,5-diphenyl-2,4-dithiobiuret (DPDB), 1-tolyl-5-phenyl-2,4-dithiobiuret (TPDB), 1-chlorophenyl-5-phenyl-2,4-dithiobiuret (CPDB), 1-anisidyl-5-phenyl-2,4-dithiobiuret (APDB) and were investigated on corrosion behavior of mild steel, stainless steel 316 and bronze in simulated corrosive environment encountered in paper industry.
This paper examines and analyzes the test results produced from a comprehensive test program designed to study on reinforced concrete corroded columns under service loads. Several small size concrete columns with various reinforcement configurations were subjected to accelerated corrosion condition in the laboratory. The measurement of electrochemical parameters, physical parameters, and chemical parameters had been thoroughly investigated in this study. After a target level of corrosion, the column specimens were tested to study the failure mode, load-strain behaviour, crack load and ultimate load. The corrosion level was measured based on the loss in weight of the reinforcement. Uncorroded columns were used as control samples and tested in parallel with the corroded samples. The results indicated that when 7%of the mass of steel is corroded the ultimate load carrying capacity is reduced upto 35% of uncorroded column under loading condition.
The hydrotransport pipes provide a flexible and more economic manner to transport oil sand slurry from excavation to the extraction plants. However, erosion-corrosion induced pipe failure constitutes a major threat to the integrity of the slurry hydrotransport system. This work reviews the erosion-corrosion phenomena encountered in oil sand slurry hydrotransport pipes. The major affecting factors and occurrence mechanism for the pipe erosion-corrosion are summarized. Furthermore, the mapping erosion-corrosion in a wide range of material-environment combinations is introduced, and the electrochemical re search approaches and techniques are analyzed. Finally, the potential protective methodology for oil sand slurry erosion-corrosion are discussed.
A thermodynamic model was developed to illustrate the interactions of stress and anodic dissolution at crack tip during carbon steel stress corrosion cracking in high temperature water in the absence and presence of oxygen by comprehensively considering the electrochemical reactions occurring inside and outside the cracks. By analyzing the change of the free-energy due to the presence of stress in the steel, it is demonstrated that a synergism of stress and anodic dissolution promotes the cracking of carbon steel. Furthermore, the presence of oxygen in the solution accelerates the crack growth by enhancing the galvanic effect between the crack wall and the crack tip. An exact expression of the stress factor is essential for the quantitative prediction of the crack growth rate.
Electrochemical oxidation of catechol was studied in the presence of piperidine as a nucleophile in water/acetonitril mixture solvents using cyclic voltammetry and square wave voltammetry methods. The results indicate that the o-benzoquinone derived from the anodic oxidation of catechol participates in Michael addition reaction with piperidine to form the corresponding catechol-piperidine adducts according to an ECE mechanism. Digital simulation of cyclic voltammograms was used to prove the proposed mechanism. Taking into account the solution electron transfer between o-benzoquinone and oxidized catechol-piperidine adduct, the values of alpha, k* and the following chemical reaction rate constant were determined.
The aim of this paper is to investigate the anodic behaviour of a chromium cast iron and the structure of the surface layer formed on the alloy in a concentrated sulfuric acid. The results derived from polarization measurements carried out in sulfuric acid at different temperatures show an anodic dissolution followed by a range of passivity. The corrosion current density i(corr) increases with increasing temperatures. SEM images show that after attack an heterogeneous film is formed on the surface alloy. EDXA analysis indicate that the main elements of the surface layer are chromium, silicon, oxygen, sulfur and carbon.
The effect of N,N'-di-o-tolylthiourea, N,N'-diphenylthiourea and N-phenylthiourea compounds on the corrosion behaviour of mild steel in 20% HCl solution was investigated using gravimetric and potentiostatic polarization techniques. The inhibition efficiency increases with increasing the concentration of inhibitors and these inhibitors are effective at high temperature.
Electrochemically alloys can be designed to produce different corrosion potentials than their alloying elements. This paper deals with investigations on the development of a stable acid chloride bath of zinc-nickel alloy on mild steel in presence of sulphamic acid as brightener. A suitable bath is reported on the basis of Hull Cell studies. The effect of bath variables and operating parameters were studied and discussed. Plating efficiency and the composition of the alloy were determined. Effects of operating parameters on the deposition characteristics and properties were also reported. The corrosion properties of zinc-nickel alloy plating were studied under different operating conditions of the bath after passivation. It was found that the optimized bath composition gave bright and smooth zinc-nickel alloy plating with high performance against corrosion.
The kinetics of anodization of zirconium have been studied in 0. 1 M sodium salicylate at various current densities 2-10 mA.cm(-2) and at various temperatures ranging from 278 to 333K using galvanostatic technique. The thickness of anodic film at a given voltage, current efficiency, differential field and breakdown voltage are found to decrease with the rise in temperature. The breakdown voltage is independent of the current density at a given temperature. The value of partial derivative(F/T)partial derivative(1/T) is observed to be independent of log.ionic current density, suggesting the applicability of Cabrera-Mott theory. The kinetic parameters of high field ionic conduction, a (half-jump distance) and W (height of energy barrier) are deduced at each temperature and are found to fall regularly with the increase of temperature. This may be attributed to the increase in the number of mobile ions with the decrease in height of energy barrier. The Tafel slope (partial derivative F/partial derivative lni) is found to decrease with increase in temperature.
Ni-Cd alloys have been electro-deposited from solution containing cationic CTAB, anionic SLS (sodium lauryl sulphate) and nonionicTX-100 (triton-X 100) to improve the surface quality of the specimens. Corrosion behavior of electrodeposited alloys in neutral solutions of boric acid (H3BO3) in 142000 ppm in presence of 2 ppm lithium hydroxide (LiOH) at 296K have been studied by, open circuit potential, linear polarization resistance, and potentiodynamic techniques. Anodic polarization curves show that the specimens exhibit quasi-passive region in all Ni-Cd samples in the potential region between about -200 mV and +200 mV (SCE) at which the current is approximately stable and dissolve trans-passivity above 200 mV (SCE). The results indicate that the samples prepared in presence of different concentrations of anionic surfactant SLS and nonionic surfactant TX-100 obviously inhibit the corrosion than those prepared in presence of different concentrations of cationic surfactant CTAB than those prepared from pure bath.
The inhibition effect of 2-chloroethylphosphonic acid (2 Cl EPA) and Zn2+ in controlling corrosion of carbon steel immersed in an aqueous solution containing 60 ppm of Cl- has been evaluated in the present study. The formulation consisting of 50 ppm of Zn2+ and 50 ppm of 2 Cl EPA has 74% inhibition efficiency (IE). The influence of pH 5, 7, 9 and I I on the inhibition efficiency of the 2 Cl EPA-Zn2+ system has also been investigated. Polarization study reveals that the 2 Cl EPA-Zn2+ system functions as a mixed inhibitor system. AC impedance spectra reveal that a protective film is formed on the metal surface. FTIR spectra reveal that the protective film consists of Fe2+ -2 Cl EPA complex and Zn(OH)(2).
Polarographic studies of copper(II) and lead(II) ions in presence of Schiff base viz. 3,4,5-Trimethoxybenzaldehyde-2-Amino-2-methyl-1,3-propanediol(TMBAMPD) as complexing agent revealed that the electrode reaction was reversible involving one and two electrons respectively at d.m.e. Lingane method was employed for the determination of stability constants and ligand number of copper-TMBAMPD and lead-TMBAMPD systems.
