In this paper, the behaviour of cavitation erosion, influence of corrosion and corrosion control on slide bearing metals for internal combustion engine were investigated, and this experiment was done by the vibratory cavitation erosion tester. The main results obtained are as follows: 1. With decreasing the space between horn and specimen, the weight loss and its rate increased step by step. But the weight loss and its rate of 0.2mm space decreased conversely more than that of 0.4mm space at early stage. 2. The weight loss and its rate with change of pH were appeared to the order of pH2>pH12>pH7>pH4. And the weight loss and its rate at pH 4 decreased at best. 3. The weight loss and its rate by cavitation erosion for bearing metals were shown to the order of W.M7>W.M1>K.M4. 4. There appeared mainly small pit hole at pH2, and appeared the pit of netting thread type at pH12 by the results of the damaged surfaces at pH2 and pH12 environments that were sensitive to cavitation erosion. 5. With increasing the viscosity of lubricating oil, the weight loss rate by cavitation erosion became dull at the space below 0.5mm. 6. The protective efficiency of cavitation erosion-corrosion is superior inhibitor of chormate(25 ppm) to cathodic protection.

Recently, with the tendency of more lightening, high-strength and high-speed in the marine industries such as marine structures, ships and chemical plants, the use of the aluminium Alloy is rapidly enlarge and there occurs much interest in the study of corrosion fatigue crack characteristics. In this paper, the initiation of surface crack and the propagation characteristics on the base metal and weld zone of 5086-H116 Aluminium Alloy Plate which is one of the Al-Mg serious alloy(A5000serious) used most when building the special vessels, were investigated by the plane bending corrosion fatigue under the environments of marine, air and applying cathodic protection. The effects of various specific resistances on the initiation, propagation behavior of corrosion fatigue crack and corrosion fatigue life in the base metal and heat affected zone were examined and its corrosion sensitivity was quantitatively obtained. The effects of corrosion on the crack depth in relation to the uniform surface crack length were also investigated. Also, the structural, mechanical and electro-chemical characteristics of the metal at the weld zone were inspected to verify the reasons of crack propagation behavior in the corrosion fatigue fracture. In addition, the effect of cathodic protection in the fracture surface of weld zone was examined fractographically by Scanning Electron Microscope(S.E.M.). The main results obtained are as follows; (1) The initial corrosion fatigue crack sensitibity under specific resistance of 25Ω.cm% show 2.22 in the base metal and 19.6 in the HEZ, and the sensitivity decreases as specific resistance increases (2) By removing reinforcement of weldment, the initiation and propagation of corrosion crack in the HAZ are delayed, and corrosion fatigue life increases. (3) As specific resistance decreases, the sensitivity difference of corrosion fatigue life in the base metal and HAZ is more susceptible than that of intial corrosion fatigue crack. (4) Experimental constant, m(Paris' rule) in the marine environment is in the range of about 3.69 to 4.26, and as specific resistance increases, thje magnitude of experimental constant, also increases and the effect by corrosion decreases. (5) Comparing surface crack length with crack depth, the crack depth toward the thickness of specimen in air is more deeply propagated than that in corrosion environment. (6) The propagation particulars of corrosion fatigue crack for HAZ under initial stress intensity factor range of δk sub(li) =27.2kgf.mm super(-3/2) and stress ratio of R=0 shows the retardative phenomenon of crack propagation by the plastic deformation at crack tip. (7) Number of stress cycles to corrosion fatigue crack initiation of the base metal and the welding heat affected zone are delayed by the cathodic protection under the natural sea water. The cathodic protection effect for corrosion fatigue crack initiation is eminent when the protection potential is -1100 mV(SCE). (8) When the protection potential E=-1100 mV(SCE), the corrosion fatigue crack propagation of welding heat affected zone is more rapid than that of the case without protection, because of the microfissure caused by welding heat cycle.

Recently with the rapid development in marine and shipbuilding industries such as marine structures, ships and chemical plants, it takes much interest in the study of corrosion fatigue characteristics that was close up an important role in mechanical design. In this study, characteristics of corner crack propagation on the base metal and heat affected zone of 5086 Al-Alloy was tested by using of a rotary bending fatigue tester and was investigated under the environments of specific resistance, σ=25Ω cm and air. The corrosion fatigue crack initiation and corrosion fatigue life sensitivity were quantitatively inspected for 5086 Al-Alloy in the specific resistance, σ=25Ω cm. Main results obtained are as follows: (1) The corrosion sensitivity of heat affected zone under specific resistance, σ=25Ωcm shows approximately 1.69~2.22 and corrosion sensitivity of base metal is more susceptible than that of heat affected zone. (2) The corrosion fatigue life sensitivity on heat affected zone decreases eminently than that of initial corrosion fatigue crack. (3) The characteristics of quarter elliptical corner crack propagation shows that depth crack is more grown than surface crack at crack initiation, but the surface crack is more propagated than depth crack as the crack propagation is increased. (4) The surface crack and depth crack growth on heat affected zone by softness show delayed phenomenon than that of base metal.

평면 굽힘부식피로 시험기를 사용하여 선박용 알루미늄합금재의 부식피로파양에 관한 연구를 한 결과 다음과 같은 결론을 얻었다. 1. 비저항이 증가함에 따라서 초기 부식피로균열발생까지의 반복회수는 지연되고, 그 부식감수성은 감소하는 양상을 나타낸다. 2. 비저항이 감소할수록 Paris rule의 실험상수 m 값은 작아지면서 응력강도 계수값에 비해 부식에 의한 영향이 더욱 민감해 진다. 3. 알루미늄 5086 합금의 부식피로균열은 입계균열파양의 양상을 보이고 있다. 4. 응력강도계수값이 증가함에 따라 부식감수성은 감소되어지고 응력강도계수값이 40kg.mm super(-3/2) 이상일 때 부식감수성은 거의 균일하게 된다.

정변위 인장시험기를 사용하여 SUS 304강 용접열 영향부의 여러 가지 염화 마그네슘용액 중에서의 SCC 발생 특성을 연구한 결과 다음과 같은 결론을 얻었다. 1) SCC 발생 잠복기간은 초기 응력강도계수 K 하(Ii) 값은 낮게 함으로써 크게 지연된다. 2) 비등 염화 마그네슘 용액 중에서의 SCC 발생은 부하와 Cl 이온의 농도에 의한 부동태 피막의 파손에 기인된다. 3) SUS 304 강 용접열 영향부의 SCC 발생 감수성은 높은 농도의 염화 마그네슘 용액일수록 온도를 낮게 함으로써 둔화된다.

접지전지 설계를 위한 Zn, Al 및 Mg의 합급양극의 특성을 실험적으로 조사한 결과를 다음과 같이 요약할 수 있다. 1. 환경비저항 1000 Ω.cm 이하에서는 Zn합금양극이, 1000 Ω.cm 이상에서는 Mg합금양극이 접지전지 설계에 좋다. 2. 비저항 500 Ω.cm 이하에서는 Al합금양극이 Mg 합금양극보다 접지전지 설계를 위한 유전양극 특성이 좋으나 모든 비저항에서 Zn합금양극보다 특성이 떨어진다. 3. 배유전유밀도가 급격히 증가하는 일정인가전압은 다음과 같다. ① E 하(Zn)=log (4.9465/σ상(0.0639))+11×10 상(-6)σ상(0.8923i) ② E 하(Al)=log (4.9306/σ상(0.0525))+13×10 상(-6)σ상(0.9314i) ˚led3 E 하(Mg)= log (3.7086/σ상(0.0988))+181×10 상(-6)σ상(0.5406i) 4. 유전양극의 종류 및 환경의 비저항에 따라 인가전압과 배유전유밀도의 관계는 다음과 같은 일반식으로 표시할 수 있다. logi=g+root(n.E+r)