Following the Leaching-out Process of Corrosion Inhibitors

Alexander Lutz, Hans Simillion, Iris De Graeve (Editor), Herman Terryn (Editor), A. Bastos (Editor), Mikhael Zheludkevich (Editor)

Research output: Chapter in Book/Report/Conference proceedingMeeting abstract (Book)Research

Abstract

To prevent corrosion on hot dip galvanized (HDG) steel most structures are protected with an organic coating. Secondly corrosion inhibitors are added underneath as conversion coatings or into the coating to give additional protection. The choice of these inhibitors is rather difficult because of too high or too low solubility and coating properties degradation. More precisely, inhibitors which perform very well in general corrosion tests, often cause problems when leaching out of the organic coatings. For example the inhibitor may be gone before the first defect appears.
In order to overcome this problem two different approaches were investigated to control the leaching out process. Microcapsules incorporated in the organic coating and filled with an inhibitor will break upon defect creation. Like this the inhibitor is immediately available in a high concentration on the spot of the highly probable corrosion onset site. Alternatively layered double hydroxides (LDH) were mixed in the coating. Through ion exchange they can be filled with an inhibitor ion. The pH change caused by the starting corrosion process results in the release of the inhibitor into the solution.
To analyze the leaching out process in detail two paths were followed. First a method was developed to create reproducible micro defects with diameters between 100 and 500 µm. Because of the size, the whole electro-active surface can be scanned with a probe within a sufficiently short time that only negligible changes take place. Different local electrochemical techniques were applied. With Scanning Vibrating Electrode Technique (SVET) the electrochemically active sites and their ionic activity could be monitored. With Scanning Ion-selective Electrode Technique (SIET) the concentration of the different ionic species (like pH and chlorides) could be determined while simultaneous SVET measurements take place.
Additionally, surface enhanced Raman spectroscopy (SERS) measurements were performed to prove the presence of the active inhibitor on the HDG steel. The high spatial resolution combined with the amplified detection limit of SERS make it an ideal method to monitor the leaching out process of an inhibitor.
Original languageEnglish
Title of host publicationEMNT 2012
Publication statusPublished - 15 Aug 2012
EventEMNT 2012 - Linz, Austria
Duration: 15 Aug 2012 → …

Conference

ConferenceEMNT 2012
CountryAustria
CityLinz
Period15/08/12 → …

Keywords

  • SVET
  • Raman
  • AFM
  • HDG steel
  • Inhibitor
  • coating

Fingerprint Dive into the research topics of 'Following the Leaching-out Process of Corrosion Inhibitors'. Together they form a unique fingerprint.

Cite this