설치형 탄약 소재의(ALDC12) 표면처리에 따른 부식특성연구

다국어 초록 (Multilingual Abstract)

Ammunition is a one-shot device product that should be stored for a long period of time and has characteristics that require high reliability. Therefore, surface treatment is essential for materials used in ammunition. Meanwhile, deployable ammunition, one of the mobile obstacles, is designed to be installed and recovered as a tactical replacement for anti-personnel mines.
We need corrosion data to identify maintenance requirements and prevent quality problems according to the operating environment and method that differed from existing weapon systems. For this purpose, we investigated the corrosion characteristics of ALDC12 alloy, a material for deployable ammunition operated in the field environment, by surface treatment. The surface treatment specimens consisted of colored chromate, soft anodizing, and control group.
First, we conducted the potentiodynamic polarization test to know the corrosion behavior of specimens according to surface treatment. It was found that all corrosion potentials were at a similar level, and the corrosion current density was confirmed to be significantly lower for anodizing than the other two surface treatments. It is assumed that surface treatment affects the current density flowing on the surface. The corrosion rate was obtained by applying Faraday's law to the two variables measured by Tafel extrapolation, and it was confirmed that the corrosion rate was lower in that order : anodizing, chromate, and control.
Afterwards, corrosion behavior was confirmed through accelerated testing. In the salt spray test, which is most commonly used in the ammunition field, it was confirmed that the two surface treatment specimens were at a similar level. Except for the control group, The weight loss values ​​were similar, and no corrosion products could be confirmed after the test was completed. The salt spray test was an environmental test for quality control, and it was judged to be limited in comparative analysis with actual corrosion data. A cyclic corrosion test was performed to obtain data close to outdoor exposure by similarly repeating actual operating conditions. The corrosion rate confirmed through weight loss values ​​was low in that order : anodizing, chromate, and control.
Corrosion in the form of spots was observed after 2 weeks for the control and chromate specimens, and from 4 weeks for the anodized specimens. In conclusion, rust was confirmed over a wide range in the chromate specimens, and fewer corrosion products were confirmed in the anodized specimens.
After the cyclic corrosion test, we observed the surface using SEM to analyze the corrosion pattern and major factors. In the chromate specimens, pitting was distributed over a shallow and wide area. On the other hand, narrow and deep pits were confirmed in the anodized specimens. Chromate treatment lowers the corrosion rate by suppressing the pH drop, but is believed to exhibit lower corrosion resistance than anodized specimens that form a strong passive film. This is judged to be consistent with the existing results that, while chromate is weakly acidic after an immersion test, soft anodic oxidation causes Al(OH)3 accumulation and aluminum ions are not supplied to the outside, resulting in a low pH drop compared to the amount of corrosion.
To confirm corrosion behavior, EDS analysis was performed at the time when pitting was identified(4 weeks) and at the time of subsequent observation(6 weeks). We performed a component analysis on the corrosion products around the pitting pits and confirmed O and Cl, and both showed an increasing trend. Therefore, it was determined that the main corrosion factor for ALDC12 alloy was the destruction of the passive film due to the influence of chlorine ions, resulting in pitting.
In conclusion, through electrochemical experiments and cycle corrosion tests, it was confirmed that anodizing had the lowest corrosion rate. To ensure ammunition supply support, it is very important point that corrosion evaluation considering the operating environment and period during the development period.

목차 (Table of Contents)

• 1. 서론 1
• 2. 이론적 배경 3
• 2.1 금속의 부식 원리 3
• 2.1.1 부식 원리 3
• 2.1.2 부식 종류 6
• 2.2 알루미늄 합금 10
• 2.3 알루미늄 합금 부식 특성 12
• 2.3.1 알루미늄 부식 특성 12
• 2.3.2 알루미늄 합금 표면처리 16
• 2.4 부식의 평가 19
• 2.4.1 탄약 분야의 부식 평가 19
• 2.4.2 전기화학적 평가 22
• 2.4.3 무게 감량 평가 24
• 3. 실험방법 27
• 3.1 재료의 선정 및 제작 27
• 3.2 동전위 분극시험 30
• 3.3 염수 분무시험 33
• 3.4 복합부식 시험 35
• 4. 실험결과 38
• 4.1 동전위 분극시험 결과 38
• 4.2 염수 분무시험 결과 44
• 4.3 복합부식 시험결과 48
• 4.4 표면 분석결과 54
• 4.5 내구수명 예측 62
• 5. 결론 64
• * 참고문헌 66
• ABSTRACT 70
• List of Table
• Table 1. EMF series 5
• Table 2.
• Chemical composition and types of die
• casting aluminum alloy (KS D 6006)
• 11
• Table 3. Chemical composition of specimen (wt%) 28
• Table 4. Surface treatment method 28
• Table 5.
• Test conditions of potentiodynamic
• polarization　
• 31
• Table 6.
• Test condition of cycle corrosion test
• (1 cycle = 12 hours)
• 36
• Table 7. Test data of potentiodynamic polarization 　 42
• Table 8. Test data of salt spray test 　　45
• Table 9. Test data of cycle corrosion test 　　49
• Table 10. Corrosion life assessment result 63