Active corrosion protection and corrosion sensing in chromate-free organic coatings

Rudolph G. Buchheit, Hong Guan, Suhakar Mahajanam, Fariaty Wong

Research output: Contribution to journalArticlepeer-review

324 Scopus citations

Abstract

In this study it is shown that anion-exchanging hydrotalcite compounds dispersed as a particulate additive in organic resins leads to potent corrosion inhibition of an underlying aluminum alloy substrate. The use of this additive also imparts the ability to detect environmental changes in the coating that are a prelude to substrate corrosion. Corrosion inhibition is derived from release of a decavanadate from crystalline Al-Zn hydroxide-based hydrotalcite particles into electrolyte that has permeated the pore space of the coating. Decavanadate release is accompanied by uptake of chloride ion in an exchange reaction. The exchange of the large decavanadate anion for the smaller chloride ion in the hydrotalcite structure results in a predictable change in crystal structure, which can be detected by X-ray diffraction. The occurrence of the decavanadate-chloride exchange reaction indicates that aggressive electrolyte has invaded the coating and that corrosion may be imminent. In this paper, methods for synthesizing an Al-Zn-decavanadate hydrotalcite particulate suitable for dispersion in an epoxy resin are described. Results from exposure and electrochemical tests illustrating corrosion protection by the hydrotalcite pigmented coatings are presented. Additionally, the characteristic changes in the X-ray diffraction pattern of hydrotalcite associated with the decavanadate-chloride exchange are presented. Diffraction patterns collected from coated Al substrates are also presented, indicating that diffraction-based interrogation of coatings is possible.

Original languageEnglish
Pages (from-to)174-182
Number of pages9
JournalProgress in Organic Coatings
Volume47
Issue number3-4
DOIs
StatePublished - Sep 2003

Bibliographical note

Funding Information:
The authors would like to thank Prof. John Olesik and members of his group for assistance with ICP-OES measurements, Dr. Valerie Laget for assistance in developing synthesis procedures for Al–Zn-decavandate hydrotalcite, and Prof. Ray Taylor with inhibitor screening experiments. This work was sponsored by the Air Force Office of Scientific Research under contract no. F49602-01-1-0352, Lt. Col. Paul Trulove, Program Manager.

Keywords

  • Chromate-free coatings
  • Corrosion inhibiting pigmets
  • Corrosion inhibition
  • Corrosion sensing
  • X-ray diffraction

ASJC Scopus subject areas

  • Chemical Engineering (all)
  • Surfaces, Coatings and Films
  • Organic Chemistry
  • Materials Chemistry

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