Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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The Effect of $Bi(OH)_3$ on Corrosion-Resistant Properties of Automotive Epoxy Primers

  • Yang, Wonseog (School of Materials Science and Engineering, Inha University) ;
  • Min, Sungki (School of Materials Science and Engineering, Inha University) ;
  • Hwang, Woon-suk (School of Materials Science and Engineering, Inha University)
  • Published : 2008.12.01
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Abstract

In this study, we evaluated anti-corrosion properties of both commercial unleaded and lead epoxy primer for automotive substrate before applying to actual painting lines by salt spray test, and cyclic corrosion test, potentiodynamic test and electrochemical impedance spectroscopy. The difference in the corrosion resistance between automotive epoxy primers contained $Bi(OH)_{3}$ and leaded one was investigated. And it was also discussed the effect of zinc phosphate pretreatment to the epoxy primers. The specimen coated epoxy primer contained $Bi(OH)_{3}$ showed 0.5 V higher corrosion potential than that of bare steel. The result of salt spray test did not indicate remarkable difference of corrosion resistance in all specimens above $10{\mu}m$ thickness up to 1200 hours. In the cyclic corrosion test, epoxy primers contained $Bi(OH)_{3}$ on phosphated substrate performed good corrosion properties until 800 hours. The epoxy primer contained $Bi(OH)_{3}$ performed the equivalent corrosion resistance as leaded coating on phosphated steel, but slightly inferior to that of leaded on bare steel. These results show that the pre-treatment of zinc phosphate is effective as well as pigment changing in performing anti-corrosion properties in automotive bodies.

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