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Effect of AlCl3, CH3SO3H on thickness, current efficiency and corrosion properties of brush plated Cr(III) formate urea baths
No full textBrush plating technique was used to deposit trivalent Cr for the first time and effects of AlCl3 and
methane sulphonic acid (CH3SO3H) in the trivalent Cr bath was studied. Advantages of brush
plated Cr on suitable substrate produced by selective area deposition process with required
thickness was investigated. Owing to its portability, flexibility and easy to operate, brush plating
has found increasing use in industry. The main applications are for repair and resizing purposes.
Brush plated Cr on brass substrate has been investigated using XRD, SEM and AFM. X-ray
diffraction analysis revealed that the brush plated Cr(110) was crystalline. Uniform surface
coverage of the substrate by granular morphology was observed from SEM and AFM. CH3SO3H
increases the hydrogen overpotential on Cr deposition, therefore current efficiency and thickness
increased. Cr coated from bath containing both AlCl3 and CH3SO3H have better corrosion
resistance due to high charge transfer resistance Rct and very low Icorr than Cr(III) bath without
these additives
Thyme extract of thymus vulgar L. as volatile corrosion inhibitor for mild steel in NaCl environment
No full textThyme extract of Thymus vulgar L. plant was used as volatile
corrosion inhibitor for mild steel in sodium chloride environment with
100 % relative humidity. The corrosion rate and inhibition efficiency
of the thyme powder was evaluated by weight loss studies and thyme
impregnated craft paper was evaluated by weight loss and
potentiodynamic polarization studies. It was found that both powder
and impregnated craft paper have significant inhibitive effect. The
inhibition efficiency increases with increase in concentration from 250
to 1000 mg for the powder and 250 to 1000 mg/sq.ft for impregnated
craft paper. This is due to adsorption of inhibitor molecule on the metal
surface. The adsorption behavior of thyme obeys Temkin's adsorption
isotherm. At higher concentration there is decrease in inhibition
efficiency. It may be due to the formation of soluble metal inhibitor
complex in NaCl environment. It has also been found that thyme
powder of concentration 1000 mg and impregnated craft paper of
concentration 1000 mg/sq.ft offered maximum inhibition efficiency of
80.49 and 78.64 %, respectively
Residence time distribution in continuous stirred tank electrochemical reactor
No full textThe aim of the present investigation is to study the electrolyte flow characteristics in a continuous stirred
tank electrochemical reactor (CSTER) using residence time distribution (RTD). The flow behavior of electrolyte
has been experimented using pulse tracer technique and the residence time distribution curves
at various operating conditions are critically analyzed. A three-parameter model has been developed to
explain the flow characteristic of electrolyte in a continuous stirred tank electrochemical reactor and the
model simulations are validated with the experimental observations
Removal of arsenic and sulphate from the copper smelting industrial effluent
No full textEffluent from the processing of arsenic-bearing ores may contain varying amounts of As(III) and As(V), oxyanion, arsenite and arsenate.
The industries are adopting the ferric arsenate precipitation; the problems aroused in this method are the formation of large amount
of sludge. The effective pH range for the precipitation of ferric arsenate is 4–8. But pH of the effluent is about 0.6 only and the sulphate
concentration is more in the effluent. Therefore it is required to raise the pH for precipitation of ferric arsenate by the addition
of an alkali. Due this reason the alkali consumption is more. The addition of chemicals may elevate the total dissolved solids (TDS)
level.
This investigation aims at the removal of arsenic (incoming contaminants levels are in the range of 1000–2000 mg/L containing other heavy metals)
from the metallurgical effluent either by electrodialysis (ED) or electrochemical ion-exchange (EIX) technique, followed by electrocoagulation
(EC). Using ED, at the current density of 2 A/dm2, arsenic can be removed up to 91.4% and sulphate up to 37.1%. Using EIX, at the current density
of 3 A/dm2, arsenic can be removed up to 58.2% and sulphate up to 72.7%. Using EC, at the current density of 1.5 A/dm2, arsenic can be removed
up to below detectable limit by atomic absorption spectrometer. By combining both the EIX and EC processes the consumption of alkali needed
to raise the pH can be effectively minimized
Longterm corrosion performance of rebar embedded in blended cement concrete under macro cell corrosion condition
No full textThe concrete does not possess sufficient resistance towards the permeation of aggressive ions when it is exposed to marine environment.
When mineral admixtures are added, they impart certain impermeability to concrete by improving the physical structure by pozzolanic
reaction. The reduction of concentration of OH ion occurs either by consumption of free Ca(OH)2 by pozzolanic reaction or by
dilution of cement alkalis due to replacement with mineral admixture. This causes a substantial reduction in the threshold value of chloride
in mineral admixed concrete. In the present investigation, the corrosion resistance of rebar embedded in concrete made with Portland
pozzolana cement (PPC), Portland slag cement (PSC) was studied for 847 days under macro cell corrosion condition with on
comparison using ordinary Portland cement (OPC). Concrete having characteristic compressive strength of 20, 30 and 40 MPa were
taken for evaluation. Potential and macro cell corrosion current were measured periodically and corrosion rates were determined by
weight-loss method. This long term experiment revealed that in 20 MPa concrete, the corrosion rate of rebar in PPC and PSC concrete
was 9 and 10 times lower than the rebar in OPC concrete: In the case of 30 MPa concrete, the corrosion rate of rebar in PPC and PSC
concrete was 17 and 6 times lower respectively and in 40 MPa concrete it was 1.6–2.5 times less than the rebar in OPC concrete. The
reduction of chloride ion content in blended cement concrete was varied from 1.4 to 3.1 times less than the OPC concrete among all
the three concretes studied. Reduction of alkalinity in 20 MPa concrete at the rebar level in PPC and PSC concrete is 6 and 10 times
lower, respectively, than in OPC concrete. In the case of 30 and 40 MPa concrete it was 2 and 1.6 times lower. The reduction in alkalinity
did not accelerate the corrosion rate of rebar in blended cement concretes even in presence of higher amount of chlorides. The apparent
chloride diffusion co-efficient of blended cement concretes was 1.6–1.8 times lower than that of OPC concrete. The combined effect of
higher chloride complexing ability and reduction of chloride ion diffusivity of blended cement concretes made them to perform better
in terms of corrosion protection of reinforcing steel
Evaluation of embeddable potential sensor for corrosion monitoring in concrete structures
No full textEmbeddable potential sensor based on MnO2 was assembled and characterised in concrete. The stability,
reversibility, polarisability and impedance characteristics have been studied with respect to known
reference. The corrosion performance of reinforced steel with respect to MnO2 sensor was monitored
by different electrochemical techniques. Reversibility of MnO2 sensor indicated that difference of ±5mV
between the forward and reverse scan indicates the better reversibility characteristics in concrete. The
rebar potentials (ER) of steel with respect to MnO2 are −315 and −525mV for passive and active conditions
of rebar in concrete. The corrosion current from potentiodynamic polarisation and Rct from a.c.
impedance technique clearly differentiated the behaviour of steel embedded in chloride contaminated
concrete (active condition) from uncontaminated concrete (passive condition) with respect to MnO2 sensor.
All these studies revealed that corrosion monitoring of steel in concrete using embedded MnO2 as a
better potential sensor for steel in concrete. In addition it is easy to fabricate for amenable miniaturisation,
varied configuration as demanded for corrosion monitoring in concrete structures
Effect of Cations of Alkali and Alkaline-Earth Metal Chlorides for Chlorine Evolution Reaction
No full textThe chlorine evolution reaction was conducted on a metal-oxide-coated titanium anode (RuO2/TiO2/SnO2) in
neutral chloride solutions of sodium, magnesium, strontium, and barium, using steady-state E-(log i) curves.
From the results, it is concluded that the chlorine evolution reaction has no dependence on the cations in
alkali and alkaline-earth metal chlorides
Brush plated ZnS films and their properties
No full textZinc sulphide thin tilms were deposited by the brush plating technique using AR grade zinc sulphate and sodium thiosulphate on titanium and conductingglasssubstratesatacurrentdensity of80mAcm-2andatdifferentdepositiontemperatures intherange30-80' C. The films exhibited cubic SlnJclure. Band gap or the films were in the range of 3.79-3.93 eV Auger spectra or the ZnS films deposited at dilTerent current densitic indicated th~t the Zn/S ratio varies in the range of 1.02-1,04, Room temperature PL spectrum of the fi Ims deposited at 80 'C indicated two emission peaks at 420 and 480 om for an excitation of 325 nm. Resistivity of the film varied from 200-769 Q cm as the deposition temperature increased
Corrosion protection of magnesium alloy ZM21 by polyaniline-blended coatings
No full textPhosphate-doped polyaniline pigment was prepared by a chemical oxidation method using ammonium persulfate in phosphoric acid media. Fourier transform infrared studies were done to characterize the pigment. The magnesium alloy ZM 21 was coated with polyaniline-pigmented paint, based on an epoxy binder, and the corrosion performance of the coating was studied by potential measurements and electrochemical imopedance spectroscopy in 0.1% and 0.5% NaCl solutions. The results were compared with strontium chromate and filler material-pigmented coatings. It was found that the coating containing polyaniline provided similar protection for the magnesium alloy as that offered by chromate-pigmented pain
Synthesis and Characterization of LiMXFe1-XPO4 (M = Cu, Sn; X = 0.02) Cathodes - A study on the Effect of Cation Substitution in LiFePO4 Material
No full textAn attempt has been made for the possible augmentation and exploration of partially substituted
LiFePO4 material as a positive electrode for lithium battery applications. In this regard, cationic
substitution of Cu and Sn (2%) to the native LiFePO4/C electro active material has been carried out
via. ball milling, with a view to understand the effect of respective transition and non-transition metals
upon LiFePO4 individually. Uniformly distributed particles (SEM) of LiMXFe1-XPO4/C (M= Cu, Sn)
with phase pure nature (XRD) and finer crystallite size (<1mm) were obtained. Further, it is interesting
to note that irrespective of the nature of the dopant metal, the simple route of ball milled LiMXFe1-
XPO4/C [M= Cu, Sn] cathodes endowed with improved conductivity and stable reversible capacity
values (chare-discharge). In other words, the LiCu0.02Fe0.98PO4/C cathode delivered a reversible
capacity of ~105 mAh/g with an excellent capacity retention characteristic. On the other hand
LiSn0.02Fe0.98PO4/C cathodes exhibited an average specific capacity of ~100mAh/g with progressively
enhanced efficiency values. Results of Fourier Transform Infra Red (FTIR) spectroscopy and Cyclic
Voltammetric studies of LiMXFe1-XPO4/C (M= Cu, Sn) composites are also appended and correlated
suitably