Formation and characteristics of Al-Zn hydrotalcite coatings on galvanized steel

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36 Scopus citations

Abstract

In this study, a process for depositing hydrotalcite (HT) coatings on galvanized steel was developed and the resulting coatings were characterized. Results showed that coatings formed spontaneously on galvanized surfaces upon exposure to ambient temperature alkaline aluminate solutions. Anodic polarization and electrochemical impedance spectroscopy experiments showed clear evidence of surface passivation. Scanning electron microscopy showed the formation of a continuous and conformal surface film comprised on a compact mass of crystallites. X-ray diffraction confirmed that the coating contained an Al-Zn hydrotalcite compound. Coating formation was enhanced by oxidizer and ammonium salt additions. Coatings formed by using best practices were deposited in less than 10 minutes and demonstrated good surface coverage and good organic coating adhesion. HT coatings formed by using best practices showed excellent organic coating adhesion compared to zinc phosphate control coatings. In salt spray testing, the presence of a hydrotalcite conversion coating under an epoxy neat resin was found to delay the onset of red rusting compared to control samples that were epoxy coated, but not conversion coated.

Original languageEnglish
Pages (from-to)277-290
Number of pages14
JournalJournal of Coatings Technology and Research
Volume1
Issue number4
DOIs
StatePublished - Oct 2004

Bibliographical note

Funding Information:
This work was supported by Concurrent Technologies Corporation, Largo, FL under contract no. 030100247, Mr. L. Gintert, program manager.

Keywords

  • Accelerated testing
  • Adhesion
  • Auto-motive-OEM
  • Cast iron
  • Conversion coating
  • Corrosion
  • Corrosion protection
  • Electrochemical impedance
  • Iron
  • Phosphate
  • Pollution
  • Steel

ASJC Scopus subject areas

  • Chemistry (all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

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