【Corrosion Technology Edition】Daily Question 20170827: Why do metals corrode?
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To boost the popularity of the Mechanical Equipment Corrosion Technology section, enhance communication among users, and enable everyone to learn together, make progress together, and improve together, we have launched the 【Question of the Day】 activity. Reward rules: 3 wealth points for replying, 10 wealth points for a correct answer. This topic is valid for two days; no score will be given if it exceeds two days. Short answer: Why do metals corrode? With very few exceptions (such as gold), which can exist in nature in their metallic form, all other metals occur in minerals as their stable compounds. When iron ore is smelted in a blast furnace, iron changes from a stable compound in the mineral to metallic iron. Iron in its metallic state is unstable under practical conditions; when exposed to the atmosphere, it spontaneously releases energy and transforms into stable compounds similar to those found in minerals. In other words, the corrosion of metal is a process of returning to a mineral state. Therefore, the corrosion process of metals is a spontaneous energy-releasing process. ============================== 【Mechanical Zone】Recruitment for moderators and technicians – applications and referrals are welcome. 【Valid indefinitely】If you’re interested, come ahead! http://bbs.hcbbs.com/thread-1568748-1-1.html
From a thermodynamic perspective, this is because the metal is in an unstable state and has a tendency to react with the surrounding medium and transform into metal ions. Thermodynamically, it can be measured by the change in Gibbs free energy ΔG during the corresponding corrosion reaction. Metallic minerals (oxides, sulfides, etc.), pure metals – the difference in energy is what drives corrosion reactions, and the corrosion process itself is a process of energy release.
Metals are damaged as a result of chemical and electrochemical actions by the surrounding medium; this phenomenon is known as metal corrosion. Metal damage caused by corrosion starts at the surface, and generally, the degree of damage is greatest at the surface as well. However, in some types of localized corrosion, such as intergranular corrosion, no visible damage to the surface can be detected with the naked eye; yet the corrosion progresses from the surface toward the interior along the grain boundaries, causing the metal to lose its strength and become damaged. This type of damage is particularly evident under stress. In nature, only a very few metals (such as gold and platinum) can exist in their free state, while most metals must be extracted from their ores using various methods. Therefore, from a thermodynamic perspective, the corrosion of box metals is a natural phenomenon
Corrosion is the process by which metal returns from its elemental state to the compounds that exist in nature (minerals). It is a spontaneous process; from an energy perspective, iron in its high-energy state is unstable, and it inevitably transforms into rust (a compound) in its lower-energy state. Corrosion is entirely a natural process that is unavoidable.
Corrosion is the process by which metal returns from its elemental state to the compounds that exist in nature (minerals). It is a spontaneous process; from an energy perspective, iron in its high-energy state is unstable, and it inevitably transforms into rust (a compound) in its lower-energy state. Corrosion is entirely a natural process that is unavoidable.
The essence of metal corrosion is that metal atoms lose electrons and become cations, that is, an oxidation reaction occurs. (1) Because metals usually contain impurities. (2) Since an unstable system formed by a metal and its environment inevitably transforms into a more stable one, corrosion occurs. (3) Because metals are inherently highly reactive
1) Because metals usually contain impurities. (2) Since the unstable system formed by metals and the environment inevitably seeks to transform into a more stable state, corrosion occurs. (3) Because metals are inherently quite reactive
Metal is damaged by the chemical and electrochemical effects of the surrounding medium; this phenomenon is known as metal corrosion. Metal damage caused by corrosion always begins at the surface, and generally, the degree of damage is greatest at the surface as well. However, in some types of localized corrosion, such as intergranular corrosion, no visible damage to the surface can be detected with the naked eye; yet the corrosion progresses from the surface toward the interior along the grain boundaries, causing the metal to lose its strength and become damaged. This type of damage is particularly evident under stress. In nature, only a very few metals (such as gold and platinum) can exist in their free state, while most metals must be extracted from their ores using various methods. Therefore, from a thermodynamic perspective, the corrosion of box metals is a natural phenomenon
The essence of metal corrosion is that metal atoms lose electrons and become cations, that is, an oxidation reaction occurs. 1) Because metals usually contain impurities. (2) Since the unstable system formed by metals and the environment inevitably seeks to transform into a more stable state, corrosion occurs. (3) Because metals are inherently quite reactive
With very few exceptions (such as gold), which can exist in nature in their metallic form, all other metals occur in minerals as their stable compounds. When iron ore is smelted in a blast furnace, iron changes from a stable compound in the mineral to metallic iron. Iron in its metallic state is unstable under practical conditions; when exposed to the atmosphere, it spontaneously releases energy and transforms into stable compounds similar to those found in minerals. In other words, the corrosion of metal is a process of returning to a mineral state. Therefore, the corrosion process of metals is a spontaneous energy-releasing process.