Why does steel rust (corrode)?

Iron’s metallic reactivity is higher than that of hydrogen; in other words, iron readily loses electrons, which is determined by its inherent chemical properties.

This post was last edited by Wang Wei2 on 2019-5-22 at 17:22. Why does metal corrode? For steel, corrosion is commonly referred to as “rusting”. But why does it rust? Further explanation is still needed. The first understanding of the causes of steel corrosion can be explained from the perspective of energy and energy levels (potential energy). All matter in nature has a natural tendency to transition from higher energy states to lower energy states (just as water flows from high places to low places); this is a law of nature. Corrosion can be understood as the process in which a material, in an environmental setting, undergoes a transition from a higher energy state to a lower energy state, and from an unstable state (metastable state) to a stable state, through physicochemical and electrochemical mechanisms. The second aspect is to explain and understand the corrosion process from an oxidation-reduction perspective. Corrosion is an oxidation process: iron turns into iron oxide (rusting), plastics, rubber, and similar materials are oxidized (aging), and even the decay of organisms and the aging of the human body (due to factors such as free radicals) are all related to oxidation processes. To provide a visual understanding and explanation of the corrosion process of steel and the significance of corrosion control. Iron ore (iron oxide in its stable state in nature) is transformed into steel (a metastable state) through smelting (which increases its energy level and consumes energy). Steel can be used as a structural material to meet mechanical requirements and the desired performance characteristics. However, in normal environments, steel in a metastable state is constantly transitioning to a lower-energy, stable state, eventually returning to its ore state (iron oxide, rust). It can be seen that without protection or with inadequate protection, the lifespan of steel is short; however, by implementing corrosion control (by taking effective protective measures), the time it remains in a stable state can be extended, allowing it to meet the expected service life requirements.