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The purpose of this paper is to understand the process of failure of scale and the corrosion resistance of scale to the substrate in an atmospheric environment.

The corrosion behaviour of X65 pipeline steel with different types of oxide scale was analysed using the natural environment exposure corrosion test, scanning electron microscopy analysis, electrochemical corrosion polarization curve test and other methods in a warehouse environment.

The results of this research show that one type of oxide scale, which is rough, has an uneven microstructure, and exhibits weak adhesion to the matrix, does not protect the substrate from corrosion. Conversely, the uniform, dense oxide scale, which exhibits strong adhesion to the matrix, provides effective protection to the steel. However, as the corrosion develops, the corrosion rate of the substrate tends to accelerate, especially when the structure of the oxide scale is damaged to a certain extent.

The corrosion mechanism of the oxide scale on hot rolled steel in an atmospheric environment has been proposed.

This study aims to develops a new-type low-alloy corrosion resistant steel containing Sb and investigate the corrosion mechanism of this new-type low-alloy steel.

Energy dispersive spectrometer, X-ray photoelectron spectroscopy, X-Ray diffraction and scanning electron microscopy were used to evaluate the corrosion resistance of the rust layers formed on these samples. Laser confocal microscopy was used to observe the corroded surfaces of the steels.

Results showed that Sb added can consume H⁺ in the solution, thereby preventing the oxygen reaction to slow down the corrosion rate. Meanwhile, a stable and insoluble substance (Sb₂O₃) in the acidic solution would be produced when the reaction of the product of Sb and H⁺ with the enough dissolved oxygen in the solution. Due to the precipitation of Sb₂O₃ and iron oxyhydroxides, the rust layer of Sb-containing steel became more uniform and compact, which resulted in better corrosion resistance in acid environment.

In this study, a new-type acid resistant low-alloy steel containing Sb was developed. Compared with the results, the corrosion mechanism of the new-type low-alloy steel in acid environment was discussed.

Global supply chains experienced unprecedented changes in 2020 and the relationship between domestic and global markets needed adjustments considering the long-term impacts of the changes that are unfolding around these markets. China has become the first country to announce a formal strategy – “Dual Circulation” Strategy (DCS) – to guide its self-reliant economic development in the post-COVID era. However, what exactly is the DCS and what drove China to publicize this strategy is not yet clear. This study aims to answer these questions.

Based on an extensive review of literature and media reports, a background has been constructed that justifies the DCS as a long-overdue historic necessity.

A novel definition of “Dual Circulation” is introduced. A novel construct to visualize the domestic circulation in light of international and domestic markets and international circulation has been presented. The study argues that maintaining optimum levels of consumption and saving rates is crucial to the DCS’s success.

The study pioneers the first scientific definition of the “Dual Circulation” that will pave way for future debate on the topic. Also, it is the first time an academic study on the DCS has been executed.