【Daily Question】12.3 Choose the option that has nothing to do with electrochemistry (2 wealth points for a reply, +3 to +8 wealth points for a correct answer)
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The last edit to this post was made by lzy4225925 on 2015-12-4 at 09:02. The Mechanical Section has introduced the \"Question of the Day\" feature, which aims to foster an active atmosphere for technical discussions and guide the direction of such exchanges. It also provides users with financial rewards, helping them experience various cool features. Topic: Which of the following phenomena is not related to electrochemical corrosion? A. Brass (a copper-zinc alloy) gongs are less prone to developing patina. B. Pig iron rusts more easily than soft iron cores (which are almost pure iron). C. Iron devices with copper fittings tend to develop rust at the points of contact. D. The surface of silver medals darkens over time. Note: We will close this thread after 24 hours, and at that time we will announce the best response as well as the answer and explanation. Charisma Reward: If you post a topic in this section within two days to provide a detailed explanation or discussion of the knowledge points related to this question, please reply or leave a comment in this post to inform us, and we will have a moderator award you charisma points. It is not allowed to simply copy and paste; original content is preferred, with at least some organization by the user along with personal insights and opinions. After registration, we will rank based on the content of the posts: the last-place contestant will receive +1 charm, the second-to-last +2 charm, and so on, with the highest score earning +5 charm. Other details: Recruitment for moderators & technicians in the [Mechanical Section] – applications and referrals are welcome. 【Valid indefinitely】【If you’re interested, come ahead!】 】(Click to enter) 【Mechanical Zone】Comprehensive guide to preventing equipment freezing over the winter 【Mechanical Zone】Call for collection of essential knowledge 【Seeking manufacturer sponsors】(Ongoing campaign) 【Rewards for recommending valuable content; the “Active Users and Weekly Stars” competition in the Mechanical Zone has begun】
D. The surface of silver medals darkens over time. In option A, brass is a copper-zinc alloy that can form a galvanic cell; however, copper is less reactive than zinc, so it is zinc that gets corroded rather than copper, and therefore patina does not form easily on copper； In option B, pig iron is an iron-carbon alloy that can form a galvanic cell, causing iron to corrode and rust; whereas a soft iron core is almost pure iron and does not form a galvanic cell ； In option C, the contact between iron and copper forms a galvanic cell; iron is more reactive than copper, and it corrodes to form rust ； The silver medal in option D is made of relatively pure silver and does not form a galvanic cell; the darkening of its surface over time is caused by reactions with various substances in the air.
D.....................................
D. The surface of silver medals darkens over time
D. (Pure silver does not form a galvanic cell) – Copper and zinc form a galvanic cell, and it is zinc that corrodes. Cast iron is an electrochemical cell composed of iron and carbon, causing the iron to corrode. Iron and copper form a galvanic cell, causing the iron to corrode.
The phenomenon that is not related to electrochemical corrosion is: D. The surface of silver medals darkens over time
The phenomenon that is not related to electrochemical corrosion is D
Choose D. Analysis: A. In brass (a copper-zinc alloy) drums, metal zinc acts as the negative electrode while metal copper serves as the positive electrode; as a result, copper is protected and less prone to corrosion. This is related to electrochemical corrosion, so A is incorrect ； B. In pig iron, metallic iron, carbon, and humid air can form a galvanic cell; metallic iron acts as the negative electrode and is prone to corrosion and rusting, which is related to electrochemical corrosion. Therefore, B is incorrect ； C. Iron devices are equipped with copper fittings, which form a galvanic cell at the points of contact; in this cell, iron acts as the negative electrode, is prone to rusting, and is subject to electrochemical corrosion, so C is incorrect ； D. The darkening of the surface of silver medals over time is due to a reaction between metallic silver and oxygen in the air, which results in the formation of silver oxide; this is a form of chemical corrosion and has nothing to do with electrochemical corrosion. Therefore, D is correct.
D. The surface of silver medals darkens over time