What is the mechanism of electrochemical corrosion?
3 Answers
Electrochemical corrosion occurs when metal materials come into contact with an electrolyte solution, leading to corrosion through electrode reactions. Here is a partial introduction to electrochemical corrosion: 1. Overview: Electrochemical corrosion is a redox reaction. In this reaction, the metal loses electrons and undergoes oxidation, a process known as the anodic reaction. The reaction products are metal ions that enter the medium or metal oxides (or insoluble metal salts) that form on the metal surface. Meanwhile, substances in the medium gain electrons from the metal surface and undergo reduction, a process known as the cathodic reaction. 2. Characteristics of the reaction process: Under certain conditions, oxidizers in non-electrolytes directly interact with atoms on the metal surface to form corrosion products.
Having driven an older car for over 20 years, I've noticed that body rust is particularly common, mainly caused by electrochemical corrosion. The process is quite similar to a small battery experiment: when there's a water film on the metal surface, one part becomes the anode, releasing electrons and getting corroded—for example, iron dissolving into iron ions—while another part becomes the cathode, absorbing electrons and oxygen to form rust. On cars, rainwater or road salt left in door seams creates micro-circuits that accelerate metal decay. Over time, the undercarriage and wheel arches are the first to suffer. Regular washing to prevent moisture buildup, along with undercoating protection, can significantly delay corrosion. In short, it's damage caused by the parallel oxidation and reduction reactions of metal in a humid environment, often overlooked but quite harmful.
After working in auto repair for a long time, it's common to see a layer of white powder on battery terminals, which is caused by electrochemical corrosion. Simply put, it involves anodic oxidation and cathodic reduction. For example, in lead-acid batteries, the positive lead plate corrodes to form lead sulfate and releases electrons, while the negative plate receives electrons and reacts with acid. In automotive circuits, when moisture or impurities intrude, a potential difference forms on the metal surface, promoting rust through natural electron flow. It's not just batteries; tube joints in the cooling system often turn green and require regular cleaning and drying. The key point is that corrosion occurs only when the current path is complete, so insulation is crucial. For prevention, using anti-rust paint or sealant is effective.
