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51318-11387-Determination of Precursor Sites for Pitting Corrosion of UNS N07718 in Cl-Environments – Part 2. Experimental Results

Electrochemical testing and in-situ microscopy using a mini-autoclave has been used to determine the precursor sites for pitting corrosion of UNS N07718 at high temperatures in chloride containing environments.

Product Number: 51318-11387-SG
Author: Luis F. Garfias-Mesias / Helmuth Sarmiento Klapper / Jutta Klöwer / Julia Botinha
Publication Date: 2018
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A novel methodology based on electrochemical testing and in-situ microscopy using a mini-autoclave has been used to determine the precursor sites for pitting corrosion of UNS N07718 at high temperatures in chloride containing environments. Simultaneous in-situ micro-visualization and electrochemical testing were done on mini-electrodes made of UNS N07718 immersed in brines while the temperature was increased to 150 °C. A real time video of the surface of the mini-electrodes was recorded while the temperature where metastable pitting initiated was obtained. The electrochemical noise arising from metastable pitting was assessed at open circuit potential conditions. In addition, potentiodynamic polarization tests were conducted at constant temperature (150 °C). This methodology allowed the determination of the precursor sites for pitting initiation (Nb rich particles) in the complex microstructure of UNS N07718.

 

Key words: Pitting, Critical Pitting Temperature, UNS N07718, Electrochemical Noise

A novel methodology based on electrochemical testing and in-situ microscopy using a mini-autoclave has been used to determine the precursor sites for pitting corrosion of UNS N07718 at high temperatures in chloride containing environments. Simultaneous in-situ micro-visualization and electrochemical testing were done on mini-electrodes made of UNS N07718 immersed in brines while the temperature was increased to 150 °C. A real time video of the surface of the mini-electrodes was recorded while the temperature where metastable pitting initiated was obtained. The electrochemical noise arising from metastable pitting was assessed at open circuit potential conditions. In addition, potentiodynamic polarization tests were conducted at constant temperature (150 °C). This methodology allowed the determination of the precursor sites for pitting initiation (Nb rich particles) in the complex microstructure of UNS N07718.

 

Key words: Pitting, Critical Pitting Temperature, UNS N07718, Electrochemical Noise

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