Mechanisms of Pitting Corrosion

Strehblow, Hans‐Henning

doi:10.1201/9780203909188.ch8

Cited by 79 publications

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“…13,14 The breakdown of the iron passivity and initiation of pitting corrosion induced by the adsorption of halide ions are of technological interest. [15][16][17][18][19][20] Due to the complex physico -chemical reaction involved, the mechanism and kinetics of passivity and pitting intiation are not fully understood. Current -potential oscillations as well as other anodic reactions associated with the physico-chemical process leading to pitting corrosion have attracted significant attention.…”

Section: Introductionmentioning

confidence: 99%

Corrosion inhibition of iron in 0.5 mol L-1 H2SO4 by halide ions

Jeyaprabha¹,

Sathiyanarayanan²,

Muralidharan³

et al. 2006

J. Braz. Chem. Soc.

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O efeito de inibição de íons haletos, tais como iodeto, brometo e cloreto, na corrosão de ferro em solução 0,5 mol L -1 de H 2 SO 4 , e o comportamento da adsorção desses íons na superfície do eletrodo, foram estudados pelos métodos de polarização e de impedância. Foi observada uma inibição de aproximadamente 90% para íons iodeto a 2,5 × 10 -3 mol L -1 e para íons brometo a 10 × 10 -3 mol L -1 , e de 80% para íons cloreto a 2,5 × 10 -3 mol L -1 . O efeito da inibição aumenta com o aumento da concentração dos íons haletos I -e Br -, mas decresce no caso do Cl -, para concentrações maiores que 5 ×10 -3 mol L -1 . Os valores de capacitância de dupla camada diminuíram consideravelmente na presença dos íons haletos, o que indicou que esses ânions são adsorvidos no ferro no potencial de corrosão.The inhibition effect of halide ions such as iodide, bromide and chloride ions on the corrosion of iron in 0.5 mol L -1 H 2 SO 4 and the adsorption behaviour of these ions on the electrode surface have been studied by polarization and impedance methods. It has been found that the inhibition of nearly 90% has been observed for iodide ions at 2.5 × 10 -3 mol L -1 , for bromide ions at 10 × 10 -3 mol L -1 and 80% for chloride ions at 2.5 × 10 -3 mol L -1 . The inhibition effect is increased with increase of halide ions concentration in the case of I -and Br -ions, whereas it has decreased in the case of Cl -ion at concentrations higher than 5 × 10 -3 mol L -1 . The double layer capacitance values have decreased considerably in the presence of halide ions which indicate that these anions are adsorbed on iron at the corrosion potential. Keywords: corrosion inhibition, iron, sulphuric acid, halide ions IntroductionAdsorption of anions over metal surfaces leading to the inhibitive or stimulation effects on metallic corrosion have been reported by earlier researchers. [1][2][3][4][5][6] It is well known that the dissolution of iron in H 2 SO 4 solutions occurs in four different states viz. active, passive, transpassive and brightening states as determined by the nature and kinetics of reaction involved, which depend on the potential and electrolyte composition. Combined adsorption of anions and cations together on the surface have also been studied. Electrostatic interaction is the main reason for the specific adsorption of anions on metal surface. 7,8 Possibility of chemisorption of the anions on metal by the formation of a covalent type bond is also suggested by Grahame. 9 Quantum chemical calculations have been used to describe the chemisorption of the halide ions on the metal electrode surface by the formation of partial charge transfer bonds. 10 Pearson suggested that the stability of the anion adsorption bond over metal surface should resemble to hard and soft acids and bases principle if the adsorption occurs by forming a donoracceptor type bond. 11,12 The specific adsorption behaviour of some of the anions on metal electrode surface and their effects on corrosion have been qualititatively related to this HSAB principle. 13,14 ...

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Section: Introductionmentioning

confidence: 99%

Corrosion inhibition of iron in 0.5 mol L-1 H2SO4 by halide ions

Jeyaprabha¹,

Sathiyanarayanan²,

Muralidharan³

et al. 2006

J. Braz. Chem. Soc.

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“…Some authors have suggested that the surface is covered by a resistive metal chloride film, which absorbs the large overpotential frequently associated with pit growth. [8][9][10] Beck has carried out studies of aluminum dissolution at high potentials in millimeterscale artificial pits, which revealed conduction and structural properties of AlCl 3 surface films found in these circumstances. 11,12 However, it is not known whether similar films are found in naturallyoccurring pits.…”

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Kinetic Model for Aluminum Dissolution in Corrosion Pits

Muthukrishnan

Hebert

2004

J. Electrochem. Soc.

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The kinetics of aluminum dissolution in etch pits and tunnels, in a 1 M HCl-3 M H 2 SO 4 solution at 70°C, were investigated. Dissolution current densities during growth of tunnels and pits, at potentials of roughly Ϫ0.8 and 1 V vs. Ag/AgCl respectively, were found to be approximately 6 A/cm 2 . Transient experiments using current step reductions during pitting, or anodic current pulses during tunnel growth, revealed strongly potential-dependent current densities up to 300 A/cm 2 . The results suggested that the dissolution rate is potential-dependent when measured on times scales of ϳ1 ms after potential disturbances, but insensitive to potential in quasi-stationary experiments. A kinetic model was presented assuming a monolayer or multilayer chloride layer on the aluminum surface, including kinetic expressions for transfer of Al ϩ3 and Cl Ϫ ions at the film/solution interface, and ionic conduction in the film. In agreement with experiments, the model yields constant or potential-dependent dissolution rates following a Butler-Volmer relation, depending on the time scale of experimental measurements. The large current densities in anodic transient experiments derived from high rates of Cl Ϫ incorporation during film growth.

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“…Pitting is particularly insidious because a component, otherwise well protected by an ultrathin oxide or oxyhydroxide barrier layer ͑i.e., the passive film͒, can be perforated locally in a short time with no appreciable forewarning sign. Extensive studies were conducted over the last 5 decades to understand pitting corrosion, [1][2][3][4][5][6][7][8][9][10] but the detailed mechanisms accounting for the local occurrence of passivity breakdown remain to be combined with kinetics laws to allow a reliable prediction. Here, we determine the kinetics laws of the interfacial reactions leading to passivity breakdown based on a model taking into account the role of the nanostructure of passive films.…”

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Breakdown Kinetics at Nanostructure Defects of Passive Films

Seyeux

Maurice

Marcus

2009

Electrochem. Solid-State Lett.

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Kinetics expressions for passivity breakdown have been determined based on a model taking into account the presence of intergranular defective sites in passive films. It is shown that depending on the interface at which the potential drop increase predominates, passivity breakdown can occur by enhanced dissolution ͑i.e., oxide thinning͒ at the oxide/electrolyte interface or by accelerated interfacial voiding at the metal/oxide interface. In all cases, the rate of the interfacial processes leading to passivity breakdown is increased at the intergranular defective sites of the passive film.

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Mechanisms of Pitting Corrosion

Cited by 79 publications

References 0 publications

Corrosion inhibition of iron in 0.5 mol L-1 H2SO4 by halide ions

Corrosion inhibition of iron in 0.5 mol L-1 H2SO4 by halide ions

Kinetic Model for Aluminum Dissolution in Corrosion Pits

Breakdown Kinetics at Nanostructure Defects of Passive Films

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