Effect of phosphate and chromate pigments on sacrificial corrosion protection by Al-Zn coating and delamination mechanism of pre-painted galvalume steel

Yu Sugawara, Kohei Araake, Izumi Muto, Michiyasu Takahashi, Masamitsu Matsumoto, Nobuyoshi Hara

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

The effect of Mg3(PO4)2 and SrCrO4 pigments in paint layer on the corrosion behavior of 55 mass% Al-Zn coating at the cut edges and the delamination mechanism of the organic paint at cross-cut areas of pre-painted galvalume steels were examined using wet/dry cycle corrosion tests. The Mg3(PO4)2 pigment did not inhibit white rust formation at the cut edges and the delamination of the organic paint. On the other hand, the SrCrO4 pigment suppressed white rust formation and improved the delamination resistance of the organic paint. Observations of the cross sections of the cross-cut area indicate that delamination was the result of the formation of corrosion products in the Al-Zn layer under the organic paint layer, thus the SrCrO4 pigment inhibited the delamination of the organic paint layer by reducing the corrosion rate of the Al-Zn layer. The Kelvin probe force microscopic measurements revealed that while the addition of the anti-corrosive pigments increased the corrosion potential of the Al-Zn layers, it did not affect the electrochemical properties of the steel substrates. The increases in the corrosion potential can be attributed to the barrier effect of the corrosion products containing chromate pigments on the Al-Zn layer against anodic dissolution. From these results, it is reasonable that chromate pigments effectively increase the delamination resistance of organic paint layers on pre-painted galvalume steels under atmospheric corrosion conditions. In addition, phosphate pigments would improve the corrosion resistance of Al-Zn layers in atmospheric environments with low chloride concentrations.

Original languageEnglish
Pages (from-to)2267-2275
Number of pages9
JournalIsij International
Volume56
Issue number12
DOIs
Publication statusPublished - 2016

Keywords

  • Chromate
  • Delamination
  • Kelvin probe force microscopy
  • Phosphate
  • Pre-painted galvalume steel
  • Sacrificial corrosion protection

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Effect of phosphate and chromate pigments on sacrificial corrosion protection by Al-Zn coating and delamination mechanism of pre-painted galvalume steel'. Together they form a unique fingerprint.

Cite this