Cleophas Akintoye Loto

Effect of ethylenediaminetetraacetic disodium dihydrate and sodium nitrite admixtures on steel-rebar corrosion in concrete

This study investigates effect of different concentrations of ethylenediaminetetraacetic disodium dihydrate (EDTA-Na2: C10H14N2Na2O8.2H2O) and sodium nitrite (NaNO2) admixtures, individually or in synergistic/partial NaNO2 replacement model, on the corrosion of concrete steel-rebar in NaCl and in H2SO4 media. Electrochemical monitoring techniques were employed for 48 steel-reinforced concrete samples immersed in the saline/marine and microbial/industrial simulating test environments for 96 days. These test data were subjected to the analyses of the Normal and the Weibull distribution fitting models, for each of which goodness of their fitting the electrochemical test data were studied using the Kolmogorov–Smirnov test statistics. Analysed results showed that EDTA-Na2 admixture concentrations exhibited better inhibition effectiveness, with relatively good effectiveness in their synergistic admixtures, than their equal-mass NaNO2 counterparts in both corrosive environments. Also, post-electrochemical experiment subjection of the concrete samples to testing and analyses of ASTM C39/C39M-03 and ASTM C267-01 showed that use of the optimally inhibiting 8 g EDTA-Na2 (per 2 × 10–3 m3 concrete) culminates in gross reduction in compressive strength of concretes in both test-media. However, lowered EDTA-Na2 concentrations exhibited better strength improvements with high corrosion inhibition in the test environments. These suggest suitability of EDTA-Na2 as an environmental-friendly NaNO2 alternative for inhibiting steel-rebar corrosion in saline/marine and microbial/industrial environments.

Electroless Nickel Plating – A Review

The operating process, versatility and the increasing research interest in optimising the process and products technology in the electroless plating method of metal coating, particularly, the electroless nickel plating of metallic substrates such as mild steel, necessitates the writing of this review. It is also aimed at providing more literature information, both of the past and the present published research in this field. In this paper, electroless nickel plating is introduced. The various nickel plating solutions and baths’ operating parameters; main types of electroless nickel plating; the mechanism involved in the plating process; application of the nickel plating process to iron powders; advantages and disadvantages and the process’s other applications are reviewed. Electroless nickel plating produces an amorphous deposit in the as-plated condition. The deposit is not dependent on current distribution and hence it is almost uniform in thickness. Electroless nickel plating is far more difficult to remove chemically than conventional nickel deposits due to its superior corrosion resistance. The deposit has a good wettability and is generally hard. However, its bath control is more complex than with electroplating. The bath also has lower efficiency and higher operating costs, even without the use of electricity.

Effect of NaNO2 and C6H15NO3 Synergistic Admixtures on Steel-Rebar Corrosion in Concrete Immersed in Aggressive Environments

This paper studies effect of different combinations of NaNO2 (sodium nitrite) and C6H15NO3 (triethanolamine (TEA)), as synergistic admixtures in concrete immersed in NaCl and in H2SO4 test environments, on the corrosion of the concrete reinforcing steel (rebar). Although statistically analysed electrochemical test results confirmed NaNO2 effectiveness, synergistic combinations of 4 g NaNO2

Inhibition of Steel-Rebar Corrosion in Industrial/Microbial Simulating-Environment by Morinda lucida

This paper studies inhibition of steel-rebar corrosion in concrete immersed in 0.5 M H2SO4, simulating industrial/microbial environment by the leaf extract of Morinda lucida. Electrochemical monitoring methods were employed for testing different concentrations of the leaf extract admixed in duplicated specimens of steel-reinforced concrete slabs immersed in the acidic test-system. Statistical analyses as per ASTM G16-95 R04 of the experimental results showed that effectiveness of Morinda lucida at inhibiting concrete steel-rebar corrosion increased with the concentration of the admixture. 0.4167% Morinda lucida, per weight of cement, was identified with optimum inhibition efficiency η = 98.78±0.34% followed in effectiveness by 0.3333% Morinda lucida with η = 93.20±1.76% at inhibiting steel-rebar corrosion in the corrosive test-environment.

Electrochemical studies of mild steel corrosion inhibition in sulfuric acid chloride by aniline

The corrosion behavior of mild steel in dilute hydrochloric acid under the inhibiting action of various concentrations of aniline was studied using the weight loss and linear polarization resistance technique. The efficiency of the inhibitor increased with the increase in the inhibitor concentration. The results obtained reveal that aniline performed effectively as a corrosion inhibitor. The adsorption mechanism indicates mixed molecular interaction from values of Gibbs free energy. The values of the inhibition efficiency calculated from the two techniques are in reasonably good agreement. The adsorption of the inhibiting compound was found to obey Langmuir, Frumkin and Freudlich adsorption isotherms. The mechanism of inhibition was discussed in the light of the chemical structure of the inhibiting compound and their adsorption on steel surfaces in relation to the potentiodynamic parameters.

Inhibition effect of Vernonia amygdalina extract on the corrosion of mild steel reinforcement in concrete in 0.2 M H2SO4 Environment

Inhibition effect of Vernonia amygdalina (bitter leaf) extract on the corrosion behaviour of embedded mild steel rebar in concrete immersed in 0.2% H2SO4 solution was investigated by potential measurement, pH and gravimetric methods using the extracts concentrations of 25, 50, 75, and 100%. The results were further analysed using the two-factor ANOVA test. Potential measurement was performed using a digital voltmeter and a copper/copper sulphate reference electrode. Compressive strength of each block sample was determined after the experiments. Weight loss values were obtained from the gravimetric method, and the inhibitor efficiency was computed from the corrosion rate of each of the tested samples. Results showed that varied concentration of V. amygdalina and the test exposure time significantly affect both the corrosion potential of embedded steel rebar in concrete and the pH of the medium. The extracts gave appreciable corrosion inhibition performance of the embedded steel rebar at 25 and 50% concentrations with the weight loss of 500 (0.5 g) and 400 mg (0.4 g) and corrosion rates values of 0.000240 and 0.000180 mm/yr, respectively. The highest inhibition efficiency (60.68%) was achieved at 50 and 39.94% at 25% concentrations, respectively. The 100 and 75% concentrations gave negative inhibitor values of −51.52 and −20.11%. The ANOVA test confirmed the results at 95% confidence, and further showed that concentration of V. amygdalina had greater effect on potential and pH measurements.

Anticorrosion performance ofAnthocleista djalonensison steel-reinforced concrete in a sulphuric-acid medium

ABSTRACT This paper employs electrochemical monitoring methods for studying the anticorrosion performance of the leaf-extract admixture of Anthocleista djalonensis (A. djalonensis) on steel-reinforced concrete immersed in the aggressive medium of a sulphuric-acid (H2SO4) test solution. The electrochemical monitoring methods employed include corrosion potential, corrosion current and corrosion rate. These were used for testing the corrosion responses of specimens of duplicated steel-reinforced concretes in the industrial/microbial simulating test environment. Analyses of these test measurements, as per American Society for Testing and Materials (ASTM) G16-95 R04, shows that the corrosion rate correlates directly with the leaf-extract admixture concentration and inverse functions of noise resistance; the ratio of the standard deviation of the corrosion potential to that of the corrosion current. It is concluded that 0.4167% A. djalonensis (per weight of cement) is the optimum modelling efficiency, from the ranked predictions of the correlation fitting model, by having an inhibition efficiency of η = 96.11 ± 1.14% (predicted) or 89.84 ± 2.46% (experimental) in the medium. Fittings of the predicted and experimental data show that they both follow the Frumkin adsorption isotherm model with a coefficient of determination r2 = 96.17% (predicted) and r2 = 89.88% (experimental). The results of the experimental and predicted model agree in support of using A. djalonensis as an eco-friendly inhibitor of corrosion in the reinforcing steel in concrete designed for the industrial/microbial service environment.

Corrosion Inhibition of Concrete Steel-Reinforcement in Saline/Marine Simulating-Environment by Rhizophora mangle L.

Corrosion inhibition of concrete steel-reinforcement in 3.5% NaCl, simulating saline/marine environment, by the leaf extract of Rhizophora mangle L. was studied in this paper. For this, duplicated specimens of steel-reinforced concrete slabs, admixed with different concentrations of the leaf extract, were immersed in the corrosive test-medium. Analyses, as per ASTM G16-95 R04, of the electrochemical test-results identified 0.0833% Rhizophora mangle L., per weight of cement, with optimal inhibition efficiency η = 95.73±0.15%. The study established a decrease in inhibition effectiveness as concentration of Rhizophora mangle L. increases.

Modelling Rhizophora Mangle L Bark-Extract Effects on Concrete Steel-Rebar in 0.5 M H2SO4: Implications on Concentration for Effective Corrosion-Inhibition

In this paper, electrochemical test-data were obtained from 0.5 M H2SO4-immersed steel-reinforced concrete admixed with different Rhizophora mangle L bark-extract concentrations and subjected to modelling analyses for studying corrosion-inhibition effectiveness. For this, macrocell current from zero-resistance ammeter and corrosion-rate from linear-polarization resistance instruments were respectively subjected to total-corrosion modelling as per ASTM G109–99a and statistical-distribution modelling as per ASTM G16–95 R04. Further analyses of these modelled test-results showed that the corrosion-rate correlated excellently (R = 95.04%, Nash-Sutcliffe efficiency = 90.33%, p-value = 0.037) with function of the bark-extract concentration and the total-corrosion from the steel-reinforced concrete samples. In agreements, both experimental and correlation fitting models identified 0.167% Rhizophora mangle L barkextract with good corrosion-inhibition efficiency, η = 73.30% (experimental) or η = 60.81% (correlation prediction). These bare implications on macrocell technique usage for complimenting identification of admixture concentration for effective corrosion-inhibition of concrete steel-rebar in the microbial/industrial simulating-environment studied.

Pyrimidine derivatives as environmentally-friendly corrosion inhibitors: A review

The perpetual quest for more efficient and environment friendly corrosion inhibitors remain a focal point in corrosion control. The use of organic compounds to inhibit corrosion has assumed great significance due to their vast applications in counteracting wastage of ferrous alloys. These compounds have shown great effectiveness for inhibiting aqueous corrosion due to film formation by adsorption on the metal surface. This paper reviews the inhibitive effect of pyrimidine derivatives as corrosion inhibitor. This class of heterocyclic aromatic organic compound has very important theoretical and practical applications. Their effect on the corrosion of metallic alloys was evaluated through assessment of various techniques and articles on their use in various investigations. The corrosion rate was found to be a function of different variables. Due attention was paid to the systematic study of inhibitor action of derivatives with much emphasis on the inhibitor type and functional groups of the molecular structure. The comprehensive discourse presented concludes, that the pyrimidine derivatives fulfill the basic requirements for consideration as an efficient corrosion inhibitor