Failure Analysis of Corroded Coating Materials by Acoustic Emission

J. Ocean Eng. Technol. 2005;19(5):43-49.

KIM GUI-SHIK;HYUN CHANG-HAE;HONG YONG-UI;SHON CHANG-HWAN;

Faculty of Mechanical, Energy and Production Eng, Cheju Nat'l Univ;Mechatronics Majors, Cheju Tourism Collage;Department of Mechanical Engineering, Univ. Jeju;Department of Mechanical Engineering, Graduate school, Cheju Nat'l Univ.;

음향방출법에 의한 용사코팅 피막부식재의 파손 해석

김귀식;현창해;홍용의;손창환;

제주대학교 기계에너지생산공학부;제주관광산업대학교 매카트로닉스학과;제주대학교 대학원 기계공학과;제주대학교 산업대학원 기계에너지공학과;

Keywords: Plasmal Spray Coating, Corroded Material, Acoustic Emission, Exfoliation

핵심용어: 플라즈마용사코팅, 부식재료, 음향방출, 박리

Abstract

This paper is to investigate the effect of corrosion by acoustic emission method in tensile loading and the adhesiveness between substrate and coating layer. The powders used are Zn and Amdry625, respectively. They are coated on brass alloy substrate. AE signals of Zn and Amdry625 coating layer increase drastically in strain $2%$. However, those of Zn specimen have more than those of Amdry625 specimen. When the specimens executed the corrosion test under $3.5%$ NaCl solution for 500, 1000 hours, the salt solution penetrated into the surface of the substrate through the pores of the coating layer. As a result, corrosion production formed on the surface of the substrate. The adhesiveness between coating layers is weakened by the polarization and corrosion itself. The AE event, count, and energy of corroded coating specimens decrease, compared to specimens without corrosion. The results are summarized as follows : 1. In the tensile tests, the time that it took to start and develop the cracks and exfoliations between the surface of the substrates and the plasma spray coatings were different according to the type of plasma sprayed material, which are Zn and Amdry625. These phenomena were obvious at the strain rate 1 to $5%$, and few available data were found after that stage. 2. The specimens with Zn coating showed the characteristics of crack, according to the changes of the tensile strength applied on the substrates while those with Amdry625 showed exfoliation as a result of low adaptation to the tensile strength. 3. The anti-corrosion specimens showed that the adhesive properties between the substrate and the plasma spray coating were strong in the order of Zn, Amdry. It showed that Corroded specimens cracked or exfoliated easily, even with the small energy, because those had a comparatively weakened adhesive property, due to corrosion. 4. Zn specimen showed no corrosion phenomena on the surface of the substrates, because they had the function of sacrifice anode however, Amdry625 specimen showed the corrosion, because it did not have that function.