The corrosion of alloy steels with different amounts of Cr was studied using electrochemical tests, wet–dry cycle corrosion, X-ray diffraction, and Kelvin probe force microscopy. The results show that the content of Cr is positively correlated with the corrosion resistance of bare steel, but the corrosion resistance of atmospheric corrosion does not show the same pattern. The atmospheric corrosion resistance of Cr-containing steel exhibits three different stages with the change of Cr element content. When the Cr content is in the range of 1–4%, the corrosion rate is high and does not change within the Cr content. As the Cr content was further increased from 4 to 7%, the corrosion rate exhibited a linear decrease and then drops rapidly when the Cr content reaches 8%. These three different corrosion rate stages are related to the influence of Cr content on Fe3O4 content in the rust layer.

Balanced development of compulsory education is not only the cornerstone of education equity, but also the fundamental part for realizing a harmonious society. There have been several achievements in balancing the development of compulsory education in China, such as narrowing the gaps in compulsory education between rural, urban, and other areas. However, the development of compulsory education is still confronted with several issues, including the gaps between rural and urban schools, the gaps between teacher's situations in rural and urban area, higher drop-out rates of rural compulsory education than that of the national average level, etc. Based on the analysis of these issues and reasons, the suggestions for the policy-makers are as follows: (1) it must be further clarified that governments at all levels must take all responsibilities for the balanced development of compulsory education so as to integrate local authorities' input and the central government's subsidies; (2) the allocation mechanism of resources for compulsory education should be set up with "qualitative and fair growth" as its aim; (3) The quality standard for compulsory education based on the national curriculum standard should be worked out for playing the role of quality inspection in the fair development of compulsory education, and a relevant system of responsibility should also be established; (4) A national unified card for compulsory education should be adopted, which would help abolish extra fees for non-permanent-resident students receiving compulsory education in other places and (5) civilian-sponsored schools should be encouraged to offer compulsory education. 470 ZENG Tianshan, et al.

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