Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Theory of metal corrosion

Mechano-chemical Effect in Chloride Corrosion of 304 Stainless Steel

Author HuangZuoZuo
Tutor TuShanDong;XuanFuZhen
School East China University of Science and Technology
Course Chemical Process Equipment
Keywords 304 stainless steel Chloride ion Uniaxial constant load Multiaxial alternating load Anodic active dissolution
Type PhD thesis
Year 2011
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With the development of the petroleum, chemical, energy plant toward the direction of high temperature, high pressure and large components of the service environment has become increasingly complex, and greatly increase in accidents caused by the corrosion is caused by corrosion of the bearing member is no sign catastrophic accident caused widespread concern. Long time, people under stress corrosion problem has been extensively studied, but due to the complexity and diversity of the interaction between the stress corrosion process, so far still a challenging problem. Based on 304 stainless steel corrosion in chloride solution as the research object around the uniaxial plastic deformation of the material surface activation dissolved multiaxial stress state the material activation dissolved and multiaxial alternating load of material corrosion , theoretical analysis and experimental research, the major progress made and conclusions are as follows: of 304 stainless steel in sodium chloride solution containing different hydrogen ion stress corrosion susceptibility to stress corrosion of 304 stainless steel in the corrosive environment Cracking mechanism. The study shows that, in 0.63mol / L NaCl 0.5mol / L HCl solution, 304 stainless steel with strong stress corrosion susceptibility. Using constant load under the electrochemical experimental studies of hydrogen and stress on the dissolution of the anode activation. Studies have shown that plastic deformation significantly accelerated the anode activation dissolved the impact of the interaction of hydrogen and stress on the anode activation dissolved. The surface electronic activity change caused by plastic deformation caused by the strain energy density and bit wrong based on the thermodynamic and electrochemical foundation, established theoretical models of the effects of hydrogen and stress on the anode activation dissolved. Constant load experiments and theoretical calculations to obtain a good agreement. To arrive at the 304 mechanism of stress corrosion cracking of austenitic stainless steel in acidic chloride solution, not hydrogen accelerated anodic dissolution. Anode activation dissolved by pitting pit complex stress state, pitting and internal stress state and local corrosion environment coupled to carry out the finite element analysis of localized corrosion pitting pit environment applied loads to explore a plus load, temperature, pitting and size distribution of the electrochemical properties of various ion concentration localized corrosion environment. The model can determine the temperature, the pitting and size as well as the applied stress localized corrosion pitting pit environment, the trend forecast for actual production practice. Multiaxial alternating load, proportional and non-proportional loading complex alternating load fatigue properties of 304 stainless steel corrosion. The study found that, compared with the proportional loading, non-proportional load from the formation of the continuous rotation of the principal stress plane loading process to the point pits impediment. However, the continuous rotation of the principal stress surfaces in non-proportional loading process so the material can not form a stable dislocation structure, raise additional strengthening of the material plays a dominant role in the formation of additional strengthening reduced fatigue life, so that the corrosion environment The effect is relatively weak. Therefore, in the same corrosive environment and stress amplitude under proportional loading fatigue life loss rate than non-proportional loading.

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