*Article* **Corrosion Behavior of Copper Bearing Steels and the Derived In-Situ Coating**

**Na Li 1,2,\*, Ling Yan 2,\*, Shaodong Wang 1, Changshun Wang 2, Hongmei Zhang 1, Fangfang Ai 2 and Zhengyi Jiang 1,3,\***


**Abstract:** Using a period immersion wet/dry cyclic corrosion test, in-situ copper-coated steels prepared by corroding copper-bearing steels were investigated in this study. The steel with a higher copper content (>3%) has a higher initial corrosion rate due to its obvious two-phase microstructure. The corrosion rates of all copper bearing steels tend to be stable after a certain time of corrosion. A copper-rich layer is formed between the matrix and the rust layer, which is due to the diffusion of copper from the rust layer to the metal surface. The copper's stability under this corrosion condition led to the formation of a thin copper-rich film, which was uncovered after removing the rust by choosing appropriate descaling reagents. The copper coating was generated from the matrix itself during the corrosion process at 25 ◦C, which provided a new approach for producing in-situ composite materials without any bonding defect. It is found that the corrosion rate, corrosion time, and copper content in steel all affect the formation of copper-rich layer. In addition to the noble copper surface, the electrochemical corrosion test results show that the corrosion resistance of copper-coated steel has been significantly improved.

**Keywords:** copper; steel; coating; descaling; corrosion; composite
