Thermal Cycling Test와 교류임피던스(EIS)법을 이용한 강교도장사양의 방식성능 평가

Abstract

Corrosion poses a serious and pervasive threat to the integrity of steel bridges. The best way to protect the bridge from corrosion is apply coatings. Performance of typical bridge coating systems has increased dramatically, and now virtually all painted steel bridges are coated with systems based on zinc-rich primers and high-performance barrier topcoats. However, a long time is often needed to predict the corrosion resistance of coatings system, especially for high performance coatings. Accelerating tests such as salt spray or Norsok M 501 require as much as 2000h exposure to qualitatively differentiate high performance samples. Thus, a faster method that can provide accurate quantitative results is needed for practical usage. In this work the thermal cycling, which consisted of a daily series of electrochemical measurements on a coated sample, performed by EIS at different temperatures. The thermal cycling test has lead to a very rapid loss of film properties. Electrochemical impedance measurements associated to this test have shown the relative importance of electrical resistance, capacitance and adhesion in predicting corrosion protective performance in steel bridge paint system. Three different kinds of coating systems were studied. Two zinc-rich primer systems topcoated with fluoropolymer and urethane. Epoxy coating has been used as a control group.