OICC Press International Journal of Industrial Chemistry 2228-5547 11 2 2023 11 17 Relationship between silicon, phosphorus content and grain number in mild steels and its corrosion resistance in pickling hydrochloric acid https://doi.org/10.1007/s40090-020-00206-0 EN Y. El Kacimi Laboratory of Materials Engineering and Environment: Application and Modeling, Faculty of Science, Ibn Tofail University, PO Box 133, 14000, Kenitra, Morocco 0000-0002-8662-4644 R. Touir Faculty of Science, Department of Chemistry, Cumhuriyet University, 58140, Sivas, Turkey M. Galai Laboratory of Materials Engineering and Environment: Application and Modeling, Faculty of Science, Ibn Tofail University, PO Box 133, 14000, Kenitra, Morocco K. Alaoui Laboratory of Materials Engineering and Environment: Application and Modeling, Faculty of Science, Ibn Tofail University, PO Box 133, 14000, Kenitra, Morocco N. Dkhireche Laboratoire d’Ingénierie des Matériaux et d’Environnement: Modélisation et Application, Faculté des sciences, Université Ibn Tofail, BP. 133, 14000, Kenitra, Morocco M. Ebn Touhami Laboratoire d’Ingénierie des Matériaux et d’Environnement: Modélisation et Application, Faculté des sciences, Université Ibn Tofail, BP. 133, 14000, Kenitra, Morocco Journal Article 2023 11 17 The micro-structural effects on the corrosion resistance of three classes of mild steels (A, B and C) suitable for galvanizing industry, according to their silicon, phosphorus content, grain number and size of carbides (Fe3C) in concentrated hydrochloride acid solution was investigated by a series of known techniques, such as potentiodynamic polarization curves, electrochemical impedance spectroscopy measurements, optical microscope and scanning electron microscopy. Results showed that the corrosion rate of the three classes of mild steel depends on their silicon and silicon/phosphorus combinations contents. It is found also that the corrosion rate depends on grain number and size of carbide content in mild steels. These findings were confirmed by micro-structural characterization and scanning electron microscopy techniques. They indicated that the severe corrosion cavities formed on the carbon steel surfaces and their sizes depended to silicon and silicon/phosphorus combinations contents. These results explained by micro-galvanic corrosion process between cementites and ferrites which became more serious with silicon and silicon/phosphorus combinations contents.