Predicting long-term durability of steel reinforced concrete with calcium nitrite corrosion inhibitor

Berke, Neal S.; Hicks, M. C.

doi:10.1016/s0958-9465(03)00038-6

Cited by 131 publications

(77 citation statements)

References 6 publications

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“…8,[12][13][14][15][16][17][18][19] Nitrite, being an oxidizing anodic inhibitor, oxidizes ferrous cations to ferric cations rapidly at anodic sites, which then precipitate out as ferric oxyhydroxides to repair defects in the passive film.…”

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confidence: 99%

Effect of Molybdate on the Passivation of Carbon Steel in Alkaline Solutions under Open-Circuit Conditions

Tan¹,

Wijesinghe

Blackwood

2016

J. Electrochem. Soc.

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The effect of molybdate on the passivation of AISI 1020 carbon steel under open-circuit conditions in pH 12.5 calcium hydroxide solutions containing chloride was investigated via electrochemical tests and surface characterization techniques. In the early stage, molybdate increased the rate of passivation, with inhibition efficiency being positive. During the later stage, after the carbon steel has passivated, precipitation of calcium molybdate over parts of the sample surface resulted in slight negative inhibition efficiency and the passive film was found to have a higher proportion of ferrous cations and a smaller thickness. However, the precipitation of a thick calcium molybdate film over the entire surface can reverse this situation, increasing the polarization resistance through a cathodic inhibition mechanism. The electrochemical and XPS results showed that regardless of its effect on the final polarization resistance, the presence of calcium molybdate precipitates led to a decrease in the total extent of carbon steel oxidation, indicating an overall beneficial effect. Molybdate was also shown to be effective against localized corrosion, with 14.6 mM molybdate sufficient in preventing passivity breakdown in pH 12.5 solution containing 564 mM chloride. Carbon steel is not a corrosion resistant alloy. However, in highly alkaline environments such as concrete, the formation of a passive oxide film on the surface reduces the corrosion rate to a very low level. 1In such environments, corrosion of carbon steel occurs mostly through two mechanisms: chloride contamination and carbonation by atmospheric CO 2 resulting in a pH drop.2-10 To counter the corrosion of carbon steel in highly alkaline environments, corrosion inhibitors can be added. Currently, calcium nitrite is being used in the construction industry as an admixed inhibitor for its set-accelerating and corrosion inhibition properties. 11Considerable research has been conducted on the inhibition of carbon steel corrosion in alkaline solutions by nitrite anions. 8,[12][13][14][15][16][17][18][19] Nitrite, being an oxidizing anodic inhibitor, oxidizes ferrous cations to ferric cations rapidly at anodic sites, which then precipitate out as ferric oxyhydroxides to repair defects in the passive film.11 Calcium nitrite works well for concrete with water to cement ratio less than 0.5 and the critical [ Despite its commercial use, concerns have been raised regarding the toxicity of calcium nitrite. 20,21 The oxidizing nature of nitrite that is essential for its corrosion inhibition effect leads to methemoglobin in humans, which is a reduction in the ability of red blood cells to transport oxygen due to Fe 2+ in hemoglobin being oxidized to Fe 3+ . This negative aspect of calcium nitrite is reflected in its being banned from use in immersed reinforced concrete structures due to toxicity and solubility issues.22 Therefore, despite calcium nitrite's commercial success as a concrete rebar inhibitor, there is an ongoing search for an alternative inhibitor for carbon st...

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confidence: 99%

Effect of Molybdate on the Passivation of Carbon Steel in Alkaline Solutions under Open-Circuit Conditions

Tan¹,

Wijesinghe

Blackwood

2016

J. Electrochem. Soc.

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“…Isso ocorreu, provavelmente, devido ao fato do inibidor não estar trabalhando em seu ponto ótimo. Complementarmente, estudos realizados por Berke e Hicks [23], ao analisar o efeito de inibidores de corrosão à base de nitrito de cálcio em ambientes agressivos de cloretos, demonstram que os resultados satisfatórios obtidos, permitem que o engenheiro projetista possa prever a durabilidade da estrutura de concreto em idades superiores a 100 anos em ambientes fortemente agressivos. Nóbrega [20] e Silva [21] explicam que os inibidores de corrosão para concreto apresentam um ponto ótimo de adição, de forma que acima ou abaixo dessa concentração tem-se comportamento inverso: aceleração do processo corrosivo em vez de mitigação.…”

Section: Síntese Dos Resultadosunclassified

Estudo de inibidores de corrosão em concreto armado

et al. 2010

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A corrosão é um fenômeno que afeta toda a sociedade, atribuindo-se uma grande importância sócio-econômica aos seus efeitos. Na área da engenharia, existem diversas conseqüências do processo corrosivo, como ocorre no aço de reforço das estruturas de concreto. Na intenção de oferecer segurança e durabilidade às estruturas, empresas do ramo químico e de produtos para construção civil disponibilizam no mercado diferentes formas de proteção à corrosão. Este trabalho apresenta análises de medidas de potencial realizadas em amostras de concreto armado, com diferentes relações água/cimento, produzidos com e sem inibidores de corrosão e expostos a dois ambientes com cloretos: em campo, exposto às intempéries da atmosfera marinha do litoral sul de Santa Catarina; em laboratório, a um processo cíclico de aceleração da corrosão através de imersão parcial (solução contendo cloretos) e secagem em estufa. Nas duas situações, foram mantidas as amostras por um período de 63 dias. A corrosão por cloretos em laboratório mostrou-se o sistema mais agressivo e eficiente para avaliar o potencial de corrosão. Os resultados buscaram caracterizar a eficiência dos inibidores de corrosão utilizados, que foram denominados de inibidor A, inibidor B e inibidor C e, ao fim das análises, foi possível classificá-los quanto ao desempenho em ambientes contaminados por cloretos em: Inibidor B > Inibidor C > Inibidor A. A redução da relação água/cimento (0,45) melhorou o desempenho do concreto de referência e dos três tipos de inibidores de corrosão utilizados. Evidenciou-se modificação das propriedades mecânicas dos concretos com inibidores, o que pode conduzir ao desenvolvimento de concretos mais impermeáveis e duráveis. Palavras-chaves:Aditivos químicos, Inibidores de corrosão, estruturas de concreto. Corrosion inhibitors study in steel-reinforced concrete ABSTRACTCorrosion is a phenomenon that affects the whole of society, such that great socioeconomic importance is attributed to its effects. In the area of the engineering, numerous consequences of the corrosive process exist, like that which occurs in steel reinforcement of concrete structures. With the intention of providing structural safety and durability, the chemical industry and companies that supply construction products market different forms of protection against corrosion. This work presents analyses of measurements of corrosive potential conducted on samples of steel-reinforced concrete, with different water/cement ratios, fabricated with and without corrosion inhibitor and exposed to two environments containing chloride: in the field, exposed to the unpredictable weather of the marine environment of the southern coastal region of Santa Catarina; and in the laboratory, exposed to a cyclical process of corrosion acceleration through partial immersion (solution containing chloride) and drying in a heater. The specimens were maintained for a period of 63 days in the respective environments. Corrosion by chloride solution in the laboratory proved to be the most aggressive and efficient s...

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“…A latter study by Skotinck (2000) and Slater (2001) showed that under long-term accelerated testing, calcium nitrite was found to be of better quality in terms of strength. Berke and Hicks (2004) further argued that 'calcium nitrite' does not increase corrosion rates after chloride protection values are surpassed and in contrast often lowers them. A major advantage to the use of calcium nitrite corrosion inhibitor is that the engineer can use rational procedures based on chloride exposure, concrete quality and quantity of calcium nitrite to design for service life on the basis of expected chloride-to-nitrite ratios.…”

Section: Basic Mechanism Of Protectionmentioning

confidence: 99%

Corrosion inhibitors for steel reinforcement in concrete: A review

Abdulrahman¹,

Ismail²,

Hussain³

2011

Sci. Res. Essays

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Inhibitors are added to concrete to improve its quality and integrity. In recent years the use of these inhibitors in producing high performance concrete has increased significantly as a result of aggressive environment. This report is based on the corrosion inhibitors used in concrete and also on the published literatures. Most authors agreed that reinforcement corrosion is the most important causes of premature failure of reinforced concrete structure worldwide and generate a great research concern due to its effects on global economy. The report presents information related to basic mechanism of corrosion protection methods to extend the service life of reinforced concrete structures which include inhibitors, sealers and barriers. Environmental sustainability issues concerning the present inhibitors being used were examined, viability and versatility of green inhibitors to concrete was also x-rayed.

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Predicting long-term durability of steel reinforced concrete with calcium nitrite corrosion inhibitor

Cited by 131 publications

References 6 publications

Effect of Molybdate on the Passivation of Carbon Steel in Alkaline Solutions under Open-Circuit Conditions

Effect of Molybdate on the Passivation of Carbon Steel in Alkaline Solutions under Open-Circuit Conditions

Estudo de inibidores de corrosão em concreto armado

Corrosion inhibitors for steel reinforcement in concrete: A review

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