Mechanical and metallurgical properties of retired 3.5NiCrMoV low pressure steam turbine discs

Stress Corrosion Cracking of Steam Turbine Steel: The Influence of Organic Acid Characteristics

“…Equation ( 33), k = A e −∆G * RT (33) where, A (m/s) is a pre-exponential factor and ∆G * (J/mol) is the activation energy for the reaction. Note the similarity of Equation (31) and Equation (33). The concentration of oxidant c O,0 in the Butler-Volmer Equation of Equation ( 32) can be identified with the hydrogen proton concentration in the hydrogen proton reduction reaction (Volmer reaction), cf.…”

“…where, δ (m) is the thickness of the diffusion layer and D (m 2 /s) is the diffusion coefficient of the reacting species, according to Equation ( 31), D = D 0 e −∆G * D RT (31) where, D 0 (m 2 /s) is a temperature-independent pre-exponential and ∆G * D (J/mol) is the activation energy for diffusion. The kinetics of the oxygen reduction reaction, cf.…”

“…The acidified first condensate in steam turbines can cause significant corrosion damage [24][25][26][27], such as acidic stress-corrosion cracking [28][29][30][31][32][33] and corrosion fatigue [34]. In addition, electrochemical impedance spectroscopy (EIS) indicated that acetic acid facilitates pitting of steam turbine steel in first condensates containing chlorides [35].…”

Effect of Film-Forming Amines on the Acidic Stress-Corrosion Cracking Resistance of Steam Turbine Steel

“…However, water treatment technologies are increasingly faced with lower quality feed waters, because of among others the ongoing shift towards alternative water sources and climate change [21][22][23][24][25]. Especially the increasing amount of organic acids in the first condensate of low-pressure steam turbine sections can cause serious corrosion damage, such as SCC [26][27][28][29][30][31][32][33][34][35]. These organic acids originate from the breakdown of organic impurities by hydrothermolysis in boilers and superheaters [19,[36][37][38][39][40][41].…”