Effect of hydrogen on the corrosion behavior of duplex stainless steel in oil and gas industry

With the gradual application of duplex stainless steel in the oil and gas industry, the application of offshore oil and gas fields and acid service conditions increases. Correspondingly, the failure risk of duplex stainless steel in a hydrogen environment gradually increases. At present, the hydrogen damage failure faced by duplex stainless steel pipelines in offshore oil and gas fields mainly occurs in seawater protects the environment through the cathodic and acidic service environment containing H2S. The introduction of hydrogen could impact the corrosion properties and microstructure of the duplex stainless steel. In addition, it inevitably suffers from hydrogen damage, including hydrogen embrittlement and hydrogen cracking. This work reviews the research status of the influence of hydrogen on duplex stainless steels, including hydrogen damage problems, corrosion properties, and microstructure changes caused by hydrogen entering duplex stainless steel, to guide the application of duplex stainless steel in the oil and gas industry in a hydrogen environment. The similarities and differences of hydrogen damage problems in duplex stainless steel under two failure scenarios are summarized. Both belong to the failure caused by hydrogen introduction: the cathodic protection environment tends to hydrogen-induced cracking, whereas the H2S environment tends to hydrogen bubbling. Measures to reduce hydrogen-induced cracking in duplex stainless steel are proposed in two situations: applying appropriate negative retention potential and controlling the H2S partial voltage. The influence of hydrogen on the corrosion behavior of duplex stainless steel is mainly manifested in the introduction of hydrogen changes the composition and structure of the passivation film, changes the type of passivation film semiconductor (from p-type to n-type) and selective corrosion, and promotes the occurrence of pitting corrosion, selective corrosion, and accelerated crevice corrosion. The influence of hydrogen on the microstructure of duplex stainless steel is manifested in hydrogen-induced phase transition (induction of martensite transition in the austenite phase and induction of ferrite phase difference microtwinning) and a sharp increase in dislocation density, which further promotes the hydrogen embrittlement of duplex stainless steel. The diffusion path and distribution of hydrogen in duplex stainless steel are the basis for understanding the correlation between local hydrogen concentration and structural changes, and the diffusion behavior of hydrogen in the two phases of duplex stainless steel is different. Moreover, austenite is regarded as a hydrogen trap because of its high solubility and low diffusion coefficient for hydrogen. The research status of hydrogen diffusion and distribution in duplex stainless steel was analyzed: the diffusion path of hydrogen in duplex stainless steel was tortuous, easily accumulated at grain boundaries, and then diffused to ferrite. Modern analytical techniques and methods related to hydrogen are introduced, focusing on two methods: the hydrogen sensitivity method and the structural characterization method. Further, the development trend of duplex stainless steel research in hydrogen environment is proposed: the corrosion behavior problem has basically reached a consensus, the hydrogen damage problem needs to be studied, and relevant theoretical mechanisms are not perfect. Thus, a new hydrogen damage theoretical model must be developed, and modern analysis technology must be combined with theoretical computational simulations.