Localized Corrosion of Passive Metals

Böhni, H.

doi:10.1002/9780470872864.ch13

Cited by 17 publications

(15 citation statements)

References 100 publications

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“…The reported passive film breakdown mechanisms can be categorized into the following three : absorption‐induced mechanism; ion migration and penetration models; mechanical film breakdown theories. …”

Section: Discussionmentioning

confidence: 99%

Effect of pH value on corrosion of carbon steel under an applied alternating current

Tang

et al. 2015

Materials & Corrosion

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In this work, corrosion behavior of carbon steel under the application of alternating current (AC) was investigated in electrolyte solutions with five different pH levels, from near-neutral to alkaline condition, through weight loss measurements, potential monitoring techniques, potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) tests, and surface examination. It is found that the corrosion rate of carbon steel decreases with increasing pH value toward the alkaline end while increases with increasing AC current density. When the solution pH becomes highly alkaline, say, 12, passivation occurs on carbon steel surfaces, with an enlarging passive region as pH increases. However, it is worth noting that the passive film suffers from mechanical breakdown when the applied AC current density reaches a critical level. Based on these results, an AC corrosion mechanism of carbon steel in near-neutral and alkaline environment is proposed.

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Section: Discussionmentioning

confidence: 99%

Effect of pH value on corrosion of carbon steel under an applied alternating current

Tang

et al. 2015

Materials & Corrosion

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“…The electromechanical film breakdown mechanism is unique considering the interpretation of AC corrosion phenomenon but is well known in the study of localized corrosion, as in the description of pitting phenomena. Generally, the theoretical models that describe the initiation process of passive film breakdown may be grouped into three classes: [31][32][33][34] (1) adsorption-induced mechanism, where the adsorption of aggressive ions as chlorides is of major importance; (2) ion migration and penetration models; and (3) mechanical film breakdown theories.…”

Section: Step 1: the Passive Film Electromechanical Breakdown Mechanismmentioning

confidence: 99%

Electro-Mechanical Breakdown Mechanism of Passive Film in Ac-Related Corrosion of Carbon Steel Under Cathodic Protection Condition

Brenna¹,

Ormellese²,

Lazzari³

2016

Corrosion

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Buried carbon steel pipe are provided with corrosion prevention systems, namely an insulating coating and a cathodic protection system which reduces (or halts) corrosion rate as a result of soil corrosiveness.The presence of alternating current (AC) interference may cause serious corrosion damages on metallic structures corresponding to coating defects, even if the -0.850 VCSE protection criterion is matched.Nowadays, the AC corrosion mechanism, as well as the protection criteria in the presence of AC, is still controversial and debated. In this paper, a two-step AC corrosion mechanism of carbon steel under cathodic protection condition is proposed: (1) AC causes the electromechanical breakdown of the passive film formed on carbon steel under overprotection condition, and (2) after passive film breakdown, high-pH chemical corrosion takes place. In order to investigate AC effects on passive condition (Step 1), experimental tests have been performed on stainless steels in neutral solution, as a result of its passive behavior: AC has harmful effects on passive condition, reducing anodic overpotential, and causing film breakdown over a critical AC interference level. The electromechanical oxide breakdown mechanism resulting from high alternating electric fields (of the order of 10 6 V/cm) within the passive film is proposed. Electrostriction stresses are a possible explanation. After film breakdown, corrosion can occur if the pH inside the crack is close to 14; this strong alkalization can be reached in overprotection condition (high cathodic current density) and in the presence of AC.

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“…The passivation process depends on the kinetics of active dissolution in a given medium, the mass transport of dissolution products, the pH and the temperature of the medium, the water content, the chemical composition, and the presence of certain chemical elements [38].…”

Section: The Open Circuit Potentialmentioning

confidence: 99%

Evaluation of Passivation Process for Stainless Steel Hypotubes Used in Coronary Angioplasty Technique

Reclaru

Ardelean

2021

Coatings

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In the manufacturing of hypotubes for coronary applications, austenitic steels of types 304, 304, or 316 L are being used. The manufacturing process involves bending steel strips into tubes and the continuous longitudinal welding of the tubes. Manufacturing also includes heat treatments and stretching operations to achieve an external/internal diameter of 0.35/0.23 mm, with a tolerance of +/− 0.01 mm. Austenitic steels are sensitive to localized corrosion (pitting, crevice, and intergranular) that results from the welding process and various heat treatments. An extremely important step is the cleaning and the internal and external passivation of the hypotube surface. During patient interventions, there is a high risk of metal cations being released in contact with human blood. The aim of this study was to evaluate the state of passivation and corrosion resistance by using electrochemical methods and specific intergranular corrosion tests (the Strauss test). There were difficulties in passivating the hypotubes and assessing the corrosion phenomena in the interior of the tubes. Assessments were made by plotting the open circuit potential curves and exploring the polarization curves in the Tafel domain range of −50 mV vs Ecorr (redox potential) and +150 mV vs saturated calomel electrode (SCE, reference micro-electrode) for both the external and the internal surfaces of the hypotubes. The tested hypotubes did not exhibit intergranular corrosion, as mass losses were low and, in general, close to the limit of the analytical balance. Electrochemical techniques made the differentiation of the passivation state of the tested hypotubes possible. The measured currents were of the order of nano–pico amperes, and the quantities of electrical charges consumed for corrosion were of the order of micro–nano coulombs.

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Localized Corrosion of Passive Metals

Cited by 17 publications

References 100 publications

Effect of pH value on corrosion of carbon steel under an applied alternating current

Effect of pH value on corrosion of carbon steel under an applied alternating current

Electro-Mechanical Breakdown Mechanism of Passive Film in Ac-Related Corrosion of Carbon Steel Under Cathodic Protection Condition

Evaluation of Passivation Process for Stainless Steel Hypotubes Used in Coronary Angioplasty Technique

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