에폭시 코팅 및 소지금속의 캐비테이션 열화 특성에 미치는 시험 조건의 영향 = Effect of test conditions on the cavitation degradation properties of epoxy coatings and base metals

다국어 초록 (Multilingual Abstract)

Because facilities such as power plants and offshore plants use seawater as cooling water, corrosion occurs due to salt and various factors in piping and heat exchangers. Carbon steel with low corrosion resistance is not used alone, but coated on the inner surface of the pipe. In the case of stainless steel with high corrosion resistance used for heat exchangers, etc., a material with high pitting resistance index is used to prevent local corrosion caused by chloride ions. Cavitation corrosion occurs in these piping and heat exchangers, causing erosion damage. Cavitation inhibits or enhances bubble formation and collapse with temperature. In addition, it is known that the higher the hardness and corrosion resistance of the material, the better the cavitation resistance. Therefore, in this study, cavitation resistance according to solution temperature and pitting resistance index in 3.5% NaCl was evaluated and analyzed for epoxy coating, carbon steel, and stainless steel. For the cavitation test, a modified method of ASTM G32 was used, and the test conditions were performed at a solution temperature of 15oC, 30oC, 45oC, and 60oC with an ultrasonic amplitude of 85μm. After the cavitation test, the deterioration rate was measured by observing the appearance, reducing the weight, and measuring the maximum damage depth. As a result of the cavitation test, the degradation rate of the epoxy coating material showed a tendency to decrease due to the effect of the cushion as the solution temperature increased. When cavitation occurs in carbon steel, the corrosion rate is greatly increased, and the temperature representing the maximum corrosion rate is lowered due to the increase in the diffusion coefficient and the rapid decrease in the amount of dissolved oxygen. In addition, the electrochemical effect and the mechanical effect occurred simultaneously, and the electrochemical effect was greater. The corrosion rate of stainless steel increased as the solution temperature increased, and as the pitting resistance index was higher than the hardness, the cavitation corrosion resistance tended to be larger.

목차 (Table of Contents)

• 제1장 서론 1
• 제2장 이론적 배경 4
• 2.1 캐비테이션 및 캐비테이션 부식 4
• 2.2 피복 5
• 2.2.1 피복 개요 5
• 2.2.2 에폭시 코팅의 캐비테이션 특성 6
• 2.3 탄소강의 부식 7
• 2.3.1 탄소강의 부식 특성 7
• 2.3.2 탄소강의 캐비테이션 부식 특성 8
• 2.4 스테인리스강의 부식 8
• 2.4.1 스테인리스강의 부식 특성 8
• 2.4.2 스테인리스강의 캐비테이션 부식 특성 9
• 제3장 연구 방법 15
• 3.1 시험편 15
• 3.2 캐비테이션 열화 시험 15
• 3.2.1 시험 장치 15
• 3.2.2 캐비테이션 열화 속도 측정 16
• 3.2.3 캐비테이션 중 전기화학적 측정 16
• 3.3 캐비테이션 열화 시험 후 형상 관찰 17
• 3.3.1 3D 영상 현미경 분석 17
• 3.3.2 SEM/EDS 분석 17
• 3.4 에폭시 코팅재 물성 평가 17
• 3.4.1 Dynamic mechanical analyzer 분석 17
• 3.4.2 Differential Scanning Calorimeter 분석 17
• 3.4.3 연속 압입 시험 18
• 3.5 경도 측정 18
• 제4장 연구결과 및 고찰 24
• 4.1 해수 배관 내면용 에폭시 코팅재의 캐비테이션 열화 특성에 미치는 용액 온도의 영향 24
• 4.2 탄소강의 캐비테이션 부식 특성에 미치는 용액 온도의 영향 및 전기화학적 캐비테이션 효과 39
• 4.3 스테인리스강의 캐비테이션 부식 거동에 미치는 공식저항지수(PRE)의 영향 51
• 제5장 결론 61
• 참고 문헌 63
• Abstract 69
• 감사의 글 71