由於世界各地反核人士的極力阻擾下，核能電廠的興建始終處於百廢待興的狀況，但隨著民眾的用電量不減反增，所以就必須仰賴現有的核能電廠延長其除役的時間，而一旦增長反應器的運轉時間，其內部組件材料就有可能遭受沿晶應力腐蝕龜裂(Intergranular Stress Corrosion Cracking, IGSCC)以及輻射促進應力腐蝕龜裂(Irradiation-Assisted Stress Corrosion Cracking, IASCC)的破壞。近十幾年來核能界發展兩種技術: 其中之一為加氫水化學（Hydrogen Water Chemistry, HWC）技術，以抑制冷卻水環境中氧化劑（氧及過氧化氫）的濃度，進而降低內部組件材料的電化學腐蝕電位(Electrochemical Corrosion Potential, ECP)，達到防制IGSCC的發生。然而HWC技術有它的瓶頸存在: 根據文獻記載，當飼水注氫量達到3 ppm時，爐心上方的ECP還是無法低於臨界腐蝕電位(-230 mV)，但不幸的是當飼水注氫量達到0.6 ppm 以上，就會帶來輻射劑量增加的副作用；另一種為HWC 技術搭配貴重金屬化學添加(Noble Metal Chemical Addition, NMCA)技術，利用貴重金屬的催化效果，來降低組件材料的ECP，但仍需要少量注氫，且有促進燃料棒護套腐蝕之問題存在。
近年來，第三種技術: 抑制性被覆(Inhibitive Protective Coatings, IPC)防蝕技術的研究逐漸盛行，雖然 IPC 技術目前尚未達到足以取代 HWC 及NMCA的具體進展，但由於採用 IPC 技術具有不須搭配HWC的優點，對注氫量的需求可能減少甚至完全免除，因此相對地運轉人員的輻射劑量亦能隨之降低，故其後續的研發成果極有可能優於 NMCA 技術。
本研究主要是模擬沸水式反應器(Boiling Water Reactor, BWRs)爐心高溫高壓環境中之電化學特性分析，並針對不同溶氧及溶氫的濃度狀態下，量測經熱敏化處理與預長氧化膜後304不□鋼方形試片與經過不同IPC處理條件後之試片的電化學動態極化掃描及表面阻抗，以比較試片沒有被覆處理與經過不同被覆溫度、顆粒大小及時間處理後所呈現的腐蝕電位及電流彼此間特性的差異，以進一步探討採用熱水沉積法的抑制性被覆之完整性，並結合X-ray、SEM、AES等儀器來觀察試片表面的氧化鋯被覆結構，以相互驗證抑制性被覆處理是否對304不□鋼產生一定的防蝕保護效果。
研究結果發現，整體而言證明抑制性的被覆效果能如預期的降低金屬的腐蝕電流密度跟氧化劑、還原劑的交換電流密度，其中又以對氧化劑的抑制效果較好。對照不同的被覆顆粒大小處理試片後，以100 nm的效果最好，700 nm的效果較差。而不同溫度的被覆處理試片，以90 ℃的效果稍微優於150 ℃。最後比較被覆時間長短的抑制效果，2週的被覆時間果然呈現出比較好的結果。但對於核電廠的實際應用，不可能長時間浪費於被覆的工作上，所以如何從這三個方向來尋找一個最佳的條件，是本實驗所努力的目標。

Intergranular stress corrosion cracking(IGSCC) of sensitized stainless steel components in boiling water reactors(BWRs) has been a major concern to worldwide BWR operators. Research has demonstrated that below a critical electrochemical corrosion potential(ECP) of -230 mVSHE, the susceptibility of stainless steel to IGSCC is dramatically reduced. In past decade, several methods have been developed to mitigate IGSCC by lowering the ECP. One is Hydrogen Water Chemistry(HWC). Hydrogen is added to the feedwater of BWRs to reduce the dissolved oxidant concentrations produced by radiolysis of water in the core of BWRs. However, several drawback of H2 addition have been discovered gradually, such as increased N16 carry-over to the turbine, higher Co60 deposition rate, high H2 cost,etc. In addition, the IGSCC protection potential(-230 mVSHE) is difficult to achieve in highly oxidizing and/ or high fluid flow regions. Another one is termed Noble Metal Chemical Addition (NMCA). But it still needs lower H2 additions to achieve a low corrosion potential (~500 mVSHE). Apart from the high cost of noble metals, the main drawback of this technology is that sufficient hydrogen level cannot be maintained in the certain locations of a BWR (e.g. in the vicinity of the core spray and top guide), Because the H2 is insufficient, NMCA may accelerate the speed of IGSCC on the contrary.
Recently, a new approach was explored to lower the corrosion potentials at all locations of BWRs, even without the presence of H2. This method is formed a dielectric films on a metal surface. It is termed Inhibitive Protective Coating (IPC).
In this study, an experiment will be conducted to investigate the effects of inhibitive coating with ZrO2 (different treating conditions) by hydrothermal deposition on Type 304 SS. The effect of ZrO2 coatings were investigated by electrochemical potentiodynamic polarization tests in simulated BWR environment. And surface analyses were conducted by X-ray、SEM、AES to identify the surface structure and components.
Test results showed that with IPC treated 304 SS specimens exhibited lower ECP、lower corrosion current density and lower exchange current density(ECD) of oxidant or reductant than the untreated specimen. Comparison the treatments of different particle size were obtained: the effectiveness of 100nm was better than 700 nm. Comparison the treatments of different deposition temperature were obtained : 90 ℃ is better than 150 ℃. Finally, Comparison the treatments of different deposition time were obtained : 2weeks is better than 1 week.

1.H. S. Kwon and A. Wuensche and D. D. Macdonald, “Effects of flow rate on crack growth in sensitized type 304 stainless steel in high-temperature aqueous solutions,” Corrosion-Vol.56, No.5, pp.482-491, 2000.
2.M.G. Fontana, Corrosion Engineering,3rded., McGraw-Hill Internation.(1983)
3.M.A.Al-Anezi, G.S.Frankel and A.K. Agrawal, ”Susceptibility of Conventional Pressure Vessel Steel to Hydrogen-Induced Cracking and Stress-Oriented Hydrogen-Induced Cracking in Hydrogen Sulfide-Containing Diglycolamine Solutions,” Corrosion . Vol.55 No.11 pp.1101-1109.
4.0. M. Shindo et al, Department of Materials Science and Engineering, Japan Atomic Energy Research Institute, “Effect of minor elements on irradiation assisted stress corrosion cracking of model austenitic stainless steels,” Journal of Nuclear Materials 233-237(1996)1393-1396.
5.M.E. Indig, Proc. 4th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors, NACE, Jekyll Island, GA., Aug.6-10, 1989, p. 4-411. 4th Int. Conf. on
6.P.L Andresen, F.P Ford, S.M. Murphy,and J.M. Perks, “State of knowledge of Radiation Effects on Environmental Cracking in Light Water Reactor Core Materials,” Environmental Degradation of Materials in Nuclear Power System–Water Reactors, NACE(Houston,TX),p.1/83-1/121(1990)
7.V. F. Baston et al., "BWR Plant-to-Fleet Water Chemistry Trends - Past and Present," Proc. 7th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, NACE, Breckenridge, Colorado, Aug. 6-10, 1995, p. 629.
8.R. L. Cowan, "The Mitigation of IGSCC of BWR Internals with Hydrogen Water Chemistry," Water Chemistry of Nuclear Reactor Systems 7, BNES, Bournemouth, England, Oct. 13-17, 1996, p. 196.
9.U. S. Nuclear Regulatory Commission, Cracking of Vertical Welds in the Core Shroud and Degraded Repair, NRC Information Notice 97-17, April 4, 1997.
10.A. Jenssen et al., “Crack Growth Behavior of Irradiated 304L Stainless Steels in Simulated BWR Environments,” Proc. 11th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, ANS, Stevenson, WA, Aug. 10-14, 2003.
11.Y. J. Kim, L. W. Niedrach, M. E. Indig, and P. L. Andresen, Journal
of Metals, Vol. 44, No. 2, p. 14 (1992).
12.S. Hettiarachchi,R.J. Law, T.P. DiaZ, R.L. Cowan, “The First In-Plant Demonstration of Noble Metal Chemical Addition Technology for IGSCC Mitigation of BWR Internal,” 8th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors, August 1014, p.535(1997)
13.Tsung-Kuang Yeh and D. D. Macdonald, "Modeling the Development of Damage in BWR Primary Coolant Circuits," Proc. 7th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, NACE, Breckenridge, Colorado, Aug. 6-10, 1995, p. 909.
14.Y. J. Kim and P. L. Andresen, "Application of Insulated Protective Coatings for Reduction of Corrosion Potential in High Temperature Water," Corrosion 96, NACE, Denver, Colorado, Mar. 24-29, 1996, Paper Number 105.
15.R. Pathania, Zirconium Oxide Deposition to Mitigate IGSCC, BWRVIP Mitigation Committee Meeting, Atlanta, GA, October 1-3, 1997, EPRI.
16.B. Stellwag, M. Lasch, and U. Staudt, “Investigation into Alternatives to Hydrogen Water Chemistry in BWR Plants,” 1998 JAIF Conference, p.186-193.
17.T. K. Yeh et al., □ Intergranular Stress Corrosion Cracking of Type 304 Stainless Steels Treated with Inhibitive Chemical in Simulated Boiling Water Reactor Environments,□ Journal of Nuclear Science and Technology, v. 39, p. 531-539 (2002).
18.J. B. Lee, Electrochemical Approach to the Corrosion Problems of Several Iron-Nickel-Chromium Alloys in High Temperature High Pressure Water, Ph.D. Thesis, Department of Metallurgical Engineering, The Ohio State University, U.S.A., 1978.
19.D.D.Macdonal et al.,”Theoretical Estimation of Crack Growth Rates in Type304 Stainless Steel in BWR Coolant Environments,” Corrosion , Vol.52 , p.768-785(1996).
20.A. J. Bard and L. R. Faulkner, “Electrochemical Methods: Fundamentals and Applications,” 2nd, John Wiley & Sons, Inc., New York, Chap. 10(2001).
21.Z.Zhou, S.N.Lvov, S.Thakur,X.Zhou, P.Chou, and R.Pathania, “Hydrothermal Deposition of Zirconia Coatings on BWR Materials for IGSCC Protection,” EPRI, Palo Alto, CA 94304.
22.S.N. Lvov,H. Gao, and D.D Macdonald, “Advanced flow-through external pressure-balance reference electrode for potentiometric and pH studies in high temperature aqueous solutions.” Journal of Electroanalytical Chemistry 443(1998) p. 186-194.
23.R.W. Bosch, W.F. Bogaerts, and J.H. Zheng, “Simple and Robust External Reference Electrodes for High-Temperature Electrochemical Measurements,”Corrosion, February, 2003, Vol.59, No.2
24.Il Soon Hwang and Chi Bum Bahn Nuclear Materials laboratory, Seoul national university, “Test Procedure for EAC-Asia Round Robin,” April 17, 2005.
25.I. G. S. Falleiros et al, “Intergranular Corrosion in a Martensitic Stainless Steel Detected by Electrochemical Tests,” Corrosion(1999)-Vol.55, No.8, pp.769-778.
26.W.L. Clarke, R.L. Cowan, and W.L. Walker, “Comparative Methode for measuring Degree of Sensitization in Stainless stell,” Intergranular Corrosion of Stainless Alloys, ASTM STP656,(1978)
27.R.Katsura et al., “DL-EPR Study of Neutron Irradiation in Type 304 Stainless Steel,”Corrosion, Vol.48,No.5,(1992)
28.C.S. Kumai, and T.M. Devine, “Oxidation of Iron in 2880C, Oxygen-Containing Water.” Corrosion. Vol. 61, No. 3.
29.D.D. Macdonald, Corrosion, Vol. 48, No. 3, p. 194 (1992).
30.Y. J. Kim and P. L. Andresen, "Application of Insulated Protective Coatings for 304SS SCC Mitigation in 2880C Water," 11th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems, Stevenson, WA, Aug. 10-14, p.526-537(2003)
31.X. Zhou, I. Balachov, and D.D. Macdonald, Corrosion Science, 40, p.1349-1362(1998)
32.Y-J.Kim and P.L. Andresen, Corrosion, 54, p.1012-1017(1988)
33.Y-J. Kim and P.L. Andresen,Corrosion/96,Paper No.105(1996)
34.P. L. Andresen, “Factors Governing The Predictoin of LWR Component SCC Behavior from Laboratory Data”,CORROSION/99, paper no. 145, Houston, TX, NACE International, (1999).
35.D. D. Macdonald et al ,” Determination of The Fate of The Current in The Stress Corrosion Cracking of Sensitized Type 304 SS in High Temperature Aqueous System”,Corrosion Science , Vol. 37, No. 1, p.189~208, (1995).
36.R. H. Jones, Metals Handbook, Vol.13, Corrosion, 9th ed., ASM International, Metals Park, OH, (1987) p.145~162.
37.P. L. Andresen, F. P. Ford, “ Life Prediction by Mechanistic Modeling and System Monitoring of Environmental Cracking of Iron Alloys in Aqueous Systems,” Materials Science and Engineering, A103, p.167, (1988).
38.D.A. Jones, Principles and Prevention of Corrosion,2nded., Prentice Hall, Upper Saddle River, Nj,1996
39.B. Stellwag, Corrosion Science, Vol. 40, No. 2, p. 337 (1998).
40.Y.-J. Kim, ”Analysis of Oxide Film Formed on Type 304 Stainless Stell in 2880C Water Containing Oxygen,Hydrogen, and Hydrogen Peroxide,” CORROSION-Vol. 55, NO.1（1999）.
41.J. Robertson, “The mechanism of high temperature aqueous corrosion of stainless steels,” Corrosion Science, Vol..32, No.4, pp.443-465,1991.
42.R. L. Cowan et al, GE Nuclear Energy, Vallecitos Nuclear Center, “Effects of hydrogen water chemistry on radiation field buildup in BWRs,” Nuclear Engineering and Design 166(1996)31-36.
43.Electric Power Research Institute, “BWR Water Chemistry Guideline, 1996 Revision,” EPRI TR-103315-R1, 1996.
44.C.C. Lin, “ Hydrogen Water Chemistry Technology in BWRS”, Proc. of the 1998 JAIF Water Chemistry Conference, JAIF, Kashiwazaki, Japan, Oct.11-16, 1998, p.211.
45.Y. J. Kim and P. L. Andresen, "Application of Insulated Protective Coatings for Reduction of Corrosion Potential in High Temperature Water," CORROSION/96, NACE, Denver, Colorado, Mar. 24-29, 1996, Paper Number 105.
46.R. Pathania, Evaluation of ZrO2 Coatings to Mitigate IGSCC, BWRVIP Mitigation Committee Meeting, Lake Buena Vista, FL, December 1-2, 1999, EPRI.
47.B. Stellwag and R. Kilian, Siemens Nuclear Power GmbH U.Staudt, VGB Germany “Investigation into Alternatives to Hydrogen Water Chemistry in BWR Plants,” 3rd Workshop on LWR Coolant Water Radiolysis and Electrochemistry.
48.R. Pathania, Zirconium Oxide Deposition to Mitigate IGSCC, BWRVIP Mitigation Committee Meeting, Atlanta, GA, October 1-3, 1997, EPRI.
49.T.K. YEH, C.H. Tsai, and Y.H Cheng. “The influence of Dissolved Hydrogen on the Corrosion of Type 304 Stainless Steels Treated with Inhibitive Chemicals in High Temperature Pure Water,” Journal of Nuclear Science and Technology, Vol. 42, No. 5, p. 462-469 (May 2005).
50.B. Stellwag, M. Lasch, and U. Staudt, 1998 JAIF Conference p186-193
51.江佳應, “沸水是反應器於加氫水化學狀態下實施催化性與抑制性被覆之防蝕效益研究,” 國立清華大學碩士論文.
52.林盈吉, “鉑覆膜之敏化304不□鋼於高溫水中應力腐蝕龜裂之研究,” 國立清華大學碩士論文.
53.李國台, “高溫加清水化學環境對鉑貴重金屬化學被覆敏化304不□鋼之應力腐蝕研究,” 國立清華大學碩士論文.
54.李明墉, “應用抑制性被覆之敏化304不□鋼於高溫純水環境中之腐蝕行為研究,” 國立清華大學碩士論文
55.柯賢文, “腐蝕及其防治.” 全華出版社