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In the present work a brief description of the mechanism development and examples of the pitting and crevice systems that have confirmed the validity of this localized acidification mechanism for stable pitting growth. Potential future lines of work are also briefly suggested.
The localized acidification mechanism for stable pitting growth was the result of the pitting research performed in the Corrosion Laboratory of the CNEA led by Dr. J.R. Galvele. The key point of the mechanism is that there is a pH drop on the anode surface and that this pH drop is a necessary condition to sustain pitting.The idea that aggressive anions lead to pitting by causing the pH at the anode to fall to values where no solid products would be formed on the metal surface has been already supported by various authors. Galvele and co-workers modified those mechanisms by taking into account the hydrolysis of the metal ions inside the pit. The analysis of the transport processes taking place inside a pit allowed to explain the pitting potentials of such metals as zinc cadmium aluminum or iron. It has also been shown that these transport process studies give a quantitative explanation of the influence of solution pH reducible ions buffer ions and inhibitors on the pitting potential and they also give an explanation of the existence of a pitting repassivation potential. In the present work a brief description of the mechanism development and examples of the pitting and crevice systems that have confirmed its validity are going to be presented.Potential future lines of work that would advance (using Galvele´s model)present understanding of several issues of pitting and crevice phenomena not yet elucidated mechanistically are also briefly suggested.
Key words: downloadable, pitting, mechanism, acidification
This paper develops the relationships between proton reduction at the surface of metals, and hydrogen evolution or hydrogen diffusion into the metal.
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The aim of this study was to determine the mechanism of atmospheric corrosion of zinc in areas of local NaCl contamination and to define the driving force of spreading of electrochemical reactions using Scanning Kelvin Probe (SKP).
A brief overview of ASTM G48 – "Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution" is used for corrosion testing in the metals industry.