Effects of Na2Cr2O7 Inhibitor on the Corrosion Potential Response of Steel Reinforced Concrete in Saline Medium

Electrochemical monitoring method of the open circuit potential was used to investigate the effect of the concentrations of Na2Cr2O7 on the corrosion potential response of steel reinforced concrete in sodium chloride medium. In the study, five different concentrations of Na2Cr2O7 admixtures were employed in a system of replicated samples of steel-reinforced concrete specimens partially immersed in 3.5% NaCl to simulate marine and saline environments. Forty days measured responses from these were subjected to the statistical analyses of the Normal and the Weibull distribution functions and tested using the Kolmogorov-Smirnov goodness of fit criteria. Results obtained from the analyses identified 4 g Na2Cr2O7 with optimal averaged potential response inhibition performance by the Normal model which showed better agreements in its models of Na2Cr2O7 potential test data than that obtained from the Weibull model of the same data. These bear pertinent implications on the need for suitability studies of appropriate statistical distribution for studying performance of corrosion inhibitors even as suggestions were proffered for addressing results conflicts among replicates of steel reinforced concrete samples employed

METHODS OF ASTM G16 AND CONFLICTS IN CORROSION TEST DATA: CASE STUDY OF NANO2 EFFECTIVENESS ON STEEL-REBAR CORROSION

In this paper, applications of the methods of ASTM G16 for addressing inherent conflicts in laboratory measurements of corrosion test data were studied, using the inhibiting effect of NaNO2 on the corrosion of concrete steel-rebar for the case study. For this, electrochemical monitoring techniques were employed for studying effectiveness of different concentrations of NaNO2 admixture in replicated concrete samples immersed in NaCl and in H2SO4 media for an experimental period of sixty-eight days. The corrosion test data from this experimental setup were subjected to the probability density fittings of the Normal and the Weibull functions as well as to significance testing methods of ASTM G16-99 R04 specifications. Results identified 10g (0.1208M) NaNO2 admixture with optimal inhibition efficiency model, η = 88.38±4.62%, in the saline/marine simulating environment and the 8 g (0.0966M) NaNO2 admixture with optimum effectiveness, η = 13.51±83.48%, in the acidic environment. The techniques of ASTM G16 adequately identified and addressed conflicting effectiveness from the test data of NaNO2 admixtures in the studied test environments

Utilization of nanochitosan in the sterilization of ponds and water treatment for aquaculture

Water pollution constitutes the leading cause of infant mortality, neonatal deformities, and shrinkage of man’s average life expectancy. Pollutants come from point and nonpoint sources; and water pollution arises from the discharge of wastewater containing undesirable impurities used for domestic, agricultural, and industrial purposes. More so, high nutrient and wastewater runoffs from fish production systems contribute to the fouling and eutrophication of recipient water bodies. Hence, aquaculture which is inextricably linked to the natural environment is challenged by the dearth of appropriate water quantity and quality, militating against fish, and fishery production. Nanochitosans as polysaccharides produced by the alkalescent deacetylation of chitin, comprise a series of 2-deoxy-2 (acetylamino) glucose linked by ß-(1-4) glycosidic linkages. They are naturally formed from the deacetylation of shellfish shells and exoskeletons of aquatic arthropods and crustaceans. The unique attributes of chitin confer a wide range of biotechnological applications on the polymer, observed in flocculation as a wastewater treatment and purification route initiated by chitosan. This chapter highlights nanochitosan properties of aquaculture relevance; and elucidates the purification potentials of nanochitosan, compared to inorganic coagulants and organic polymeric flocculants. Effects of chitosan on contaminants and microorganisms, as well as applications in fish pathogens detection, fish disease diagnosis, and control are discussed

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: C 10H14N2Na2O8.2H 2O) 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 × 10-3m3 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. © 2013 Copyright Taylor and Francis Group, LLC

Inhibition and compressive-strength performance of Na2Cr2O7 and C10H14N2Na2O8·2H2O in steel-reinforced concrete in corrosive environments

This paper studied corrosion-inhibition and compressive-strength performances of Na2Cr2O7 (sodium dichromate) and C10H14N2Na2O8·2H2O (ethylenediaminetetraacetic disodium salt: EDTA-Na2) admixtures in steel-reinforced concrete immersed in NaCl and in H2SO4 corrosive environments. Electrochemical methods were used for studying corrosion responses of different concentrations of the individual admixtures and their synergies, in the model that partially replace the toxic Na2Cr2O7 by the environmentally-friendly C10H14N2Na2O8·2H2O, in steel-reinforced concretes. After the electrochemical experiment, the steel-reinforced concrete samples were subjected to the compressive-strength testing and analyses of ASTM C39/C39M-03 and ASTM C267-01(2012). Results showed that the use of environmentally-friendly EDTA-Na2 for partially replacing toxic Na2Cr2O7 chemical exhibited better corrosion-inhibition and compressive-strength improvement in the NaCl-immersed concretes, than in the H2SO4-immersed concretes. The 2 g Na2Cr2O7 + 6 g EDTA-Na2 admixture (representing partial replacement model of 6 g Na2Cr2O7 by 6 g EDTA-Na2) exhibited optimal corrosion inhibition efficiency (η = 99.0%) and very good compressive-strength improvement advantage in the NaCl-immersed concretes. In contrast, comparatively low compressive-strength reduction tradeoff with the good inhibition effectiveness of η = 79.9% support use of 6 g EDTA-Na2 admixture only (i.e., without Na2Cr2O7 addition) for inhibiting reinforcing-steel corrosion in the H2SO4-immersed concretes

Methods of ASTM G16 and conflicts in corrosion test data: Case study of NaNO2 effectiveness on steel-rebar corrosion

In this paper, applications of the methods of ASTM G16 for addressing inherent conflicts in laboratory measurements of corrosion test data were studied, using the inhibiting effect of NaNO2 on the corrosion of concrete steel-rebar for the case study. For this, electrochemical monitoring techniques were employed for studying effectiveness of different concentrations of NaNO2 admixture in replicated concrete samples immersed in NaCl and in H2SO4 media for an experimental period of sixty-eight days. The corrosion test data from this experimental setup were subjected to the probability density fittings of the Normal and the Weibull functions as well as to significance testing methods of ASTM G16-99 R04 specifications. Results identified 10g (0.1208M) NaNO2 admixture with optimal inhibition efficiency model, η = 88.38±4.62%, in the saline/marine simulating environment and the 8 g (0.0966M) NaNO2 admixture with optimum effectiveness, η = 13.51±83.48%, in the acidic environment. The techniques of ASTM G16 adequately identified and addressed conflicting effectiveness from the test data of NaNO2 admixtures in the studied test environments. [email protected]

Lethal Doses and Histopathological Changes in Liver and Kidney of Healthy Clarias gariepinus Sub-adult Exposed to Red Allium cepa Linn. Bulb

Adverse effects of Allium cepa bulb has been well overlooked because it is natural and assumed safe. This study investigated the lethal doses and histopathological changes in liver and kidney of healthy Clarias gariepinus sub-adult exposed to red Allium cepa bulb at varying concentrations (200, 150, 100, 50 and 25 g/kg) of A. cepa via diet and bath (5, 3, 1.5, 0.7 and 0.4 g/L) for two weeks. Specimens were sacrificed, liver and kidneys collected, processed and examined for histopathological changes. Proximate analysis, qualitative and quantitative phytochemistry was determined using standard methods. Brine Shrimp lethality assay (BSLA), LD50 and LC50 of the onion on experimental fish were investigated. Saponins, tannins, phenols, flavonoids and alkaloids were present. LC50 of the onion extract was between 0. 51 mg and 0.64 mg in the BSLA while mean LD50 and LC50 for dietary and bath treatments were 447.1 g/kg and 12.2 g/L. Liver histopathology showed vacuolar degeneration of the hepatocytes and congestion of central vein, while necrosis of the epithelial cells and haemosiderosis were observed in the kidney at high concentrations. Allium cepa is safe in fish when administered in lower dose either through diet or bath exposure but was toxic at high dose