離岸風機水下基礎結構以裸鋼形式浸置於海水中，因與鄰近海平面水下基礎塗裝區表面狀態差異緣故，水下結構之腐蝕行為，會隨愈接近海平面而有增加之趨勢。為遏止裸鋼之腐蝕並提升運維之安全性，裸鋼需依陰極防蝕工法，藉由耦合活性較裸鋼高的金屬(如鋁)，作為犧牲陽極錠進行陽極反應並發生腐蝕消耗，使裸鋼表面成為陰極以抑制水下結構腐蝕發生。犧牲陽極錠會隨布點距離及隨時間消耗，致使裸鋼的陰極保護電位退化及保護效能退化；此外，風力與洋流的反覆應力作用，使風機結構發生疲勞行為。應力的影響會加速陽極腐蝕或陰極防蝕的電化學反應速率，前者導致水下基礎結構弱化，後者則可能誘發氫還原反應，進而引發水下結構氫誘發延遲破裂。因此，本研究藉由鄰近塗裝區之裸鋼，於人工海水外加不同陰極保護電位之疲勞行為研究，分別確認陰極保護對裸鋼的腐蝕反應抑制，及應力對裸鋼陰極保護氫脆敏感性影響，建立有效的陰極保護關鍵技術，確保離岸風機結構運維安全。於開路電位(Open Circuit Potential, OCP)約-0.80 VCSE，亦即不施以陰極保護且進行裸材腐蝕疲勞時，量測其電流密度為正值，裸材不但發生陽極腐蝕且導致疲勞斷裂；當外加陰極保護電位時，量測裸材電流密度值為負，顯示其表面發生水溶液氫還原的陰極反應為主。當外加電位為-0.85 VCSE時，即可形成陰極保護且裸材不發生腐蝕疲勞斷裂。當陰極保護電位降至-1.25 VCSE，則未發生氫誘發腐蝕疲勞失效，在此有效的陰極保護電位範圍內，水下基礎結構可免於發生腐蝕誘發疲勞斷裂與氫誘發疲勞斷裂。

The offshore wind turbine is submerged under seawater, and the bare carbon steel surface is affect by the seawater. The condition of the steel surface is different between the area under seawater and the area at the tidal zone. Due to the proximity to sea level, the degree of corrosion of the bare steel is enhanced. To prevent corrosion and increase structural security, cathodic protection is used, treating the bare steel as the cathodic and consuming sacrificial anode ingot as the anode. The sacrificial anode ingot degrades over time and setting distance, reducing the cathodic protection ability. Additionally, the stress effects of wind and ocean currents on the offshore wind turbine structure induce fatigue behavior, accelerating electrochemical reactions. This can lead to corrosion fatigue or hydrogen-induced embrittlement at the anode or cathodic condition. Therefore, an investigation of cathodic protection under seawater of bare steel with applied fatigue stress and different cathodic potential is used to clarify the resistance to corrosion and the effect of hydrogen-induced embrittlement. When the bare steel is at open-circuit-potential (OCP at -0.80 VCSE) in seawater without cathodic protection, a positive current is measured during corrosion fatigue, leading to anode corrosion and eventual failure. Conversely, a negative current density is detected when corrosion fatigue occurs under cathodic protection, indicating hydrogen reduction reaction on the bare steel surface. At an applied potential of -0.85 VCSE, the structure under seawater can be cathodically protected, and the bare steel can sustain corrosion fatigue up to its fatigue limit without failure. When the cathodic potential is increased to -1.25 VCSE, increasing cathodic reduction does not induce hydrogen-induced embrittlement on the bare steel. Therefore, under effective cathodic protection, neither corrosion nor hydrogen-induced embrittlement of bare steel would occur.