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The dissolution–ionization–diffusion–deposition (DIDD) model was used for developing a corrosion–resistant stainless steel (SS) by the means of alloying and the guidelines for the process were proposed. The novel HP–13Cr–Cu SS was designed to resist corrosion in H 2 S–containing geothermal environment. The results indicated that the preferential deposition of CuS promoted the heterogeneous nucleation rate of Cr 2 O 3 , FeCr 2 O 3 , and FeS, which formed denser corrosion product layer. As a result, this alloy exhibited a low corrosion rate and a high sulfide stress cracking (SSC) resistance. The results were consistent with the theoretical calculation conducted by the DIDD model. • The DIDD model established the bridge between thermodynamics and kinetics of electrochemical corrosion. • The guidelines for designing corrosion–resistance stainless steel were proposed by means of micro–alloying. • A novel HP–13Cr–Cu SS was designed based on the DIDD model to resistant the H 2 S corrosion. • The testing results verified HP–13Cr–Cu SS gained the low corrosion rate and high SSC resistance. [ABSTRACT FROM AUTHOR]

The dissolution-ionization-diffusion-deposition (DIDD) model is corrected by a cathodic process with the feature of complex equilibrium and deposition competition. CO 2 /H 2 S corrosion of steel is taken as an example to better understand whether the main factor controlling the corrosion is CO 2 , H 2 S or both. The preliminary assessment reveals that when the rate of nuclei is less than 10 % of the total, the corrosion is controlled by only one factor. Furthermore, the calculated results also have a good agreement with morphology and weight loss experiments. This study makes a significant contribution to promoting the application of DIDD model. • The DIDD model is corrected with a complex cathodic process and deposition competition. • When the FeCO 3 nuclei rate is less than 10 %, the corrosion is controlled by H 2 S. • When the FeS nuclei rate is less than 10 %, corrosion is controlled by CO 2 , otherwise controlled by both. • Taking CO 2 /H 2 S corrosion of 20 steel as an example to validate the corrected model. [ABSTRACT FROM AUTHOR]

• TG201 inhibitor contains Cu2+, and would acquire electrode prior to H+ to form Cu film in the process of acidizing. • The galvanic corrosion between HP-13Cr SS and Cu film could be neglected. • The failure mechanism resulted in the synergistic effect resulted from the Cu film among the process of well completion. • With the temperature and pressure increased, the corrosion rate and the synergistic effect would be enhanced obviously. TG-201 inhibitor could minimize corrosion of HP-13Cr SS in the process of live acid. Moreover, it accelerated the probability of serious corrosion of SS during the well completion. The failure mechanism of TG-201 inhibitor was investigated using surface analysis and electrochemical measurements. TG201 inhibitor contains amounts of Cu2+, which would acquire the electrons prior to H+ to form Cu film. The failure mechanism was due to the synergistic effect attributed to the Cu film. Cu film promoted the formation of the occluded cell and the changes of fluid state evoked by the increase in interfacial roughness during the well completion. [ABSTRACT FROM AUTHOR]

• A 45-degree elbow results in a region of low velocity, high pressure and high turbulence energy. • The change in the flow state leads to the condensation of water vapor. • The synergistic effect of electrochemical corrosion and stress corrosion evokes the incident. • Changing the structure will reduce the condensation of vapor can improve the life of pipeline. A bursting incident occurred in a 45-degree elbow of a natural gas gathering pipeline in an oilfield. The failure analysis was performed by means of corrosion morphology observation, corrosion products analysis, and computational fluid dynamics (CFD) simulations. The results showed that a radical change in the fluid state at the 45-degree elbow due to its climbing structure and formation a region of low flow velocity, high pressure and high turbulence kinetic energy, which promoted the condensation of water vapor containing CO 2. Then the corrosive water droplets flowed back under the action of gravity and accumulated at the junction between the elbow and horizontal pipeline. In such a corrosive medium, electrochemical corrosion was preferred for 20 steel. In addition, the junction of the horizontal pipe and the inclined pipe exhibits higher structural stress concentration, resulting in increased corrosion thinning. Finally, the failure of the pipeline can be attributed to the synergistic effect of electrochemical corrosion and stress accelerated corrosion. [ABSTRACT FROM AUTHOR]

• The corrosion rate of 308L SS decreased first and then increased after the thermal-aged, thermal-aged and irradiated process. • The thermal-aged 308L SS performed a compacter and thicker passive film with the much more stable compounds. • After the thermal-aged and irradiated process, the thickness of the passive film decreased and the unstable NiOOH formed. Effect of thermal aging and irradiation on the corrosion behavior of 308L stainless steel (SS) in simulated pressurized water reactor (PWR) environment was investigated by using electrochemical techniques and surface analysis. The results delineated that the corrosion susceptibility of 308L SS decreased first and then increased obviously after the thermal-aged, thermal-aged and irradiated process, respectively. It can be attribute to variation of the microstructure and composition of the passive film. Compared with the 308L SS, the thermal-aged ones performed a compacter passive film characteristic with oxide Cr 2 O 3 , Fe 2 O 3 and hydroxide Ni(OH) 3. Whereas, after the thermal-aged and irradiated process, the thickness of the passive film decreased obviously and the hydroxide Ni(OH) 3 transform to the unstable NiOOH. As a result, performing higher corrosion susceptibility once more. [ABSTRACT FROM AUTHOR]