Browsing by Author "R.S. Chaudhary"

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CORROSION RESISTANCE OF TWO MAGNETIC METALLIC GLASSES IN ACIDIC AND NEUTRAL AQUEOUS SOLUTIONS.
(1986) I.B. Singh; R.S. Chaudhary; T.K.G. Namboodhiri
The corrosion resistance of two magnetic metallic glasses, viz. Fe//4//0Ni//4//0B//2//0 and Fe//3//9Ni//3//9Mo//2 (SiB)//2//0 was evaluated in H//2SO//4 and NaCl solutions by weight loss measurement and electrochemical techniques. In exposures up to six days the corrosion rate of Fe//4//0Ni//4//0B//2//0 was about 5 mpy while Fe//3//0Ni//3//9Mo//2 (SiB)//2//0 corroded about two times faster in 0. 1 M H//2SO//4 solution. In 3. 5% NaCl both alloys corroded at about the same rate, nearly 2 mpy. In potentiostatic polarization measurements the Mo bearing alloy passivated in the potential range plus 0. 45 V to plus 1. 45 V with respect to saturated calomel electrode in H//2SO//4 solutions of concentration 0. 001 M to 0. 1 M, but both alloys failed to passivate in NaCl solutions.
Effect of alloying on the corrosion behaviour of FeB metallic glasses in sulphuric acid
(1986) I.B. Singh; R.S. Chaudhary; T.K.G. Namboodhiri
The corrosion behaviour of seven metallic glasses based on the FeB system, namely (i) Fe40Ni40B20 (Vitrovac 0040), (ii) Fe40Ni38Mo4B18 (Metglas 2826MB), (iii) Fe39Ni39Mo2(SiB)20 (Vitrovac 4040), (iv) Fe40Ni40P14B6 (Metglas 2826), (v) Fe32Ni36Cr14P12B6 (Metglas 2826A), (vi) Fe78B13Si9 (Metglas 2605-S-2) and (vii) Fe67Co18B14Si1 (Metglas 2605Co), was investigated in H2SO4 solutions of various concentrations (0.001-0.1 M) using mass loss and electrochemical techniques. In exposures of up to 6 days the corrosion rate in 0.1 M H2SO4 changed in the following order: 2826A < 2826 < 0040 < 2826MB < 4040 < 2605Co < 2605-S-2. During anodic polarization the alloys 2605-S-2, 2605Co and 0040 did not exhibit passivation whereas the remaining four alloys passivated in all the H2SO4 solutions used. Icorr, Icrit and Ipass for these metallic glasses were found to be dependent on the concentration of the corrodent. Icorr and Icrit for all the alloys decreased with decreasing H2SO4 concentration. Ipass for Metglas 2826 and 2826MB increased with decreasing acid concentration while the opposite effect was found for the other two passivating alloys. The present results showed that the corrosion resistance of FB-based metallic glasses depends on the alloying elements present in them. Their corrosion resistance increased by alloying with metals whose effectiveness increased in the following order: cobalt, molybdenum, nickel and chromium. Similarly, metalloids were effective in increasing corrosion resistance in the following order: silicon, boron and phosphorus. The passive film formed on Metglas 2826A alloy was found to be more stable than those on alloys 2826, 2826MB and 4040. © 1986.
EFFECT OF SOME ANIONS ON THE CORROSION CHARACTERISTICS OF Fe//4//0Ni//4//0B//2//0 METALLIC GLASS.
(1986) I.B. Singh; T.K.G. Namboodhiri; R.S. Chaudhary
The corrosion behavior of Fe//4//0Ni//4//0B//2//0(0040) metallic glass in the presence of sodium salts of Na//2SO//4, Na//2CO//3, Na//2HPO//4, NaNO//3, Na//2MoO//4, Na//2WO//4 and Na//2CrO//4 was investigated. The open circuit potential (OCP) variation in solutions containing these salts in concentration from 0. 1 M to 0. 001 M were measured up to 2 hours. The anodic polarization curves of the alloy have been recorded under potentiostatic condition. The OCP shifted towards the noble direction in presence of chromate and tungstate while towards the active direction in the case of the other anions in ennobling the alloy under OCP conditions.
ELECTROCHEMICAL AND AES INVESTIGATIONS OF SOME METALLIC GLASSES IN SULPHURIC ACID SOLUTION.
(1987) I.B. Singh; R.D.K. Misra; T.K.G. Namboodhiri; R.S. Chaudhary
No passivation is observed for 0040 alloy whereas all the other alloys passivated in sulphuric acid solutions. Initial dissolution of the alloy in the active region is essential for passivation in molybdenum containing alloys and the concentration of Mo in the passive film is less than that of in the bulk of the alloys. Better passivation is observed in 2826 alloy when the dissolution rate is high in the active region. Prepassive film on 2826MB and 2826 alloys is nickel rich which changes to iron rich passive film at higher anodic potentials. In 2826A alloy, chromium and phosphorous concentrations are higher in the passive film.
ELECTROCHEMICAL AND AES INVESTIGATIONS OF SOME METALLIC GLASSES IN SULPHURIC ACID SOLUTION.
(1987) I.B. Singh; R.D.K. Misra; T.K.G. Namboodhiri; R.S. Chaudhary
No passivation is observed for 0040 alloy whereas all the other alloys passivated in sulphuric acid solutions. Initial dissolution of the alloy in the active region is essential for passivation in molybdenum containing alloys and the concentration of Mo in the passive film is less than that of in the bulk of the alloys. Better passivation is observed in 2826 alloy when the dissolution rate is high in the active region. Prepassive film on 2826MB and 2826 alloys is nickel rich which changes to iron rich passive film at higher anodic potentials. In 2826A alloy, chromium and phosphorous concentrations are higher in the passive film.
Influence of some metal ions on dissolution behaviour of aluminium-iron alloy in orthophosphoric acid
(1995) R.S. Dubey; S.N. Upadhyay; R.S. Chaudhary
Dissolution behaviour of aluminium-iron alloy was studied by weight loss and potentiostatic techniques at 30 +/-0.5 degrees C. The corrosion rate increases with acid concentration, immersion period and temperature. The effect of some metal ions (Cu"SUP 2+" , Zn"SUP 2+" , Cr"SUP 3+" , Mn"SUP 2+" , Na"SUP +" , K"SUP +" and Mg"SUP 2+" ) was studied in 1.00% orthophosphoric acid. All the metal ions except Cu"SUP 2+" stifled the dissolution of aluminium and the inhibition efficiency increased with increasing the metal ion concentration. (from Authors)
INHIBITIVE ACTION OF PIPERIDINE ON HSLA STEEL CORROSION AND HYDROGEN EVOLUTION REACTION IN H//2SO//4 MEDIA.
(1987) Reeta Agrawal; R.S. Chaudhary; T.K.G. Namboodhiri
A study of the corrosion behavior of HSLA steel in 1N-H//2SO//4 solution suggest that piperidine acts as a good inhibitor for corrosion and hydrogen evolution reaction (h. e. r. ). The rate of h. e. r. on HSLA steel was found to be of first order with respect to left bracket H** plus right bracket . The corrosion current decreases with increasing concentration of piperidine. The adsorption of piperidine on the surface of the steel follows Langmuir adsorption isotherm.
INHIBITIVE ACTION OF SOME MERCAPTANS TOWARDS THE CORROSION AND DEZINCIFICATION OF 60/40, 63/37 & 70/30 BRASSES IN 13. 4 N NH4OH.
(Natl Research Council of Canada, 1984) Pushpa Gupta; R.S. Chaudhary; T.K.G. Namboodhiri; B. Prakash
The inhibitory action of benzyl, n-butyl, sec. butyl mercaptans and 2-mercapto ethanol towards the corrosion and dezincification has been investigated, using weight loss, solution analysis and potentiostatic techniques. All the inhibitors are effective to reduce the corrosion of brasses, only benzyl mercaptan and 2-mercapto ethanol are effective to minimize the dezincification in brasses. These chemicals inhibit both anodic as well as cathodic reactions, indicating a mixed type of inhibition.
Inhibitive action of various azoles on the corrosion of mild steel in sulphuric acid. 2
(1990) R.H. Chaturvedi; R.S. Chaudhary
This paper presents the second part of the discussion on the results of experiments carried out to determine the inhibitive action of various azoles on the corrosion of mild steel in sulfuric acid. For all the azole compounds studied, the inhibitive efficiency increases with temperature from 30°C to 50°C. This efficiency may be due to two reasons: A higher activation energy is available for adsorption at higher temperatures; and surface coverage is enhanced at higher temperatures by the inhibitor molecules.
SOME ASPECTS OF CORROSION AND ITS CONTROL IN TUBEWELLS.
(1984) M.S. Narayanaswamy; R.S. Chaudhary
Groundwater recovery through tubewells is a major source of drinking water for rural as well as urban communities in India. Although the average life expectancy of a tubewell may vary from 15 to 20 years (with a maximum of 40 years), some fail earlier because of poor design, incrustation of screens and corrosion. The problem of corrosion in tubewells and its remedy, which is often neglected, is in India primarily due to the quality of water, other factors being the composite materials in pipes and pumps, and the nature of soil. In addition to economic losses, corrosion in tubewell causes several management problems. Attention is drawn to the causes of corrosion in well and experiences in limiting corrosion through control measures are briefly reviewed.
Untersuchungen zum Einfluß des Stahlgefüges auf die instationäre Wasserstoffpermeation
(1981) R.S. Chaudhary; E. Riecke
Der Einfluß des Gefügezustandes des Eisens und eines niedriglegierten Stahles auf die Wasserstoffpermeation bei Raumtemperatur wird mit Hilfe der elektrochemischen Permeationsmethode untersucht. Die Transportvorgänge im Werkstoff während der Wasserstoffbeladung oder ‐effusion werden durch die Gefügeelemente und den Wasserstoffgehalt beeinflußt. Die in Abhängigkeit vom Werkstoffzustand ermittelten Diffusionskoeffizienten überstreichen bis zu fünf Zehnerpotenzen. Bei instationärer Diffusion bewirken Versetzungen und Phasengrenzen einen Abfall des effektiven Diffusionskoeffizienten auf Werte zwischen 10−7 und 10−9 cm2/s. Bei stationärer Permeation werden Diffusionskoeffizienten zwischen 10−5 and 10−4 cm2/s erreicht. Copyright © 1981 Verlag GmbH & Co. KGaA, Weinheim