Journal of the Korean institute of surface engineering (한국표면공학회지)

The Korean Institute of Surface Engineering (한국표면공학회)
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Characteristics of Conversion Coating of AZ31 Magnesium Alloy Formed in Chromium-Free Cerium-Based Solution

크롬 프리 세륨 용액에 의한 AZ31 마그네슘 합금의 화성 피막에 대한 특성 평가

  • Kim, Myung Hwan (Korea Institute of Industrial Technology(KITECH)) ;
  • Lee, Dong Uk (Department of Industrial Chemistry, Pukyong National University) ;
  • Kwag, Sam-Tag (Department of Industrial Chemistry, Pukyong National University) ;
  • Moon, Myung-Jun (Department of Industrial Chemistry, Pukyong National University)
  • Received : 2016.02.02
  • Accepted : 2016.02.25
  • Published : 2016.02.29
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Abstract

A chromium-free Ce-based conversion coating formed by immersion in a solution containing cerium chloride and nitric acid on AZ31 magnesium alloy has been studied. The effects of acid pickling on the morphology and the corrosion resistance of the cerium conversion coating were investigated. The corrosion resistance of the conversion coating prepared on AZ31 Mg alloy after organic acid pickling was better than that of inorganic acid pickling. The morphology of the conversion-coated layer was observed using optical microscope and SEM. Results show that the conversion coatings are relatively uniform and continuous, with thickness 1.0 to $1.1{\mu}m$. The main elements of the conversion coating of AZ31 Mg alloy are Mg, O, Al, Ce and Zn by EDS analysis. The electrochemical polarization results showed that the Ce-based conversion coating could reduce the corrosion activity of the AZ31 Mg alloy substrates in the presence of chloride ions.

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