什么是电镀?
电导体是允许电流轻松通过的材料。电导率是物质使电流流过它的能力的量度。固体金属和石墨是具有高导电性的良好电导体。有些液体也是良导体。已经净化或蒸馏的水是电的不良导体。然而,即使是少量的污染物(盐和矿物质)也会使水成为良好的导体,因为它包含带电的离子。因此,来自水龙头、水井、池塘、河流、海洋、湖泊和其他水体的水由于污染物而带电。酸、碱和盐溶液构成了导电液体的大部分。当电流通过它们时,导电溶液中的分子会分解成离子。离子是带正电或带负电的原子或原子团。由于这些离子,液体中会发生导电。在我们了解电镀是什么之前,最好先回顾一下电流化学效应的一些基本概念:
电解质
电解质是一种通过分解成带正电和带负电的粒子(称为离子)来传输电流的物质,这些粒子向电路的负极和正极端子(阴极和阳极)迁移并正常放电。酸、碱和盐是最著名的电解质,它们在溶于水或酒精时会电离。当在没有任何溶剂的情况下熔化时,许多盐,如氯化钠,表现为电解质;还有一些,例如碘化银,即使在固态下也是电解质。
电极
电极是一种固体电导体,通过非金属材料、液体、气体、等离子体和真空导电。电极通常是良好的电导体,但它们不必由金属制成。
Cathode and Anode
At the electrodes of an electrochemical cell, reduction and oxidation reactions occur. The cathode is the electrode where the reduction takes place. The anode is where oxidation takes place.
The direction in which a cell functions determines whether an electrode is a cathode or an anode.
When a cell switches from acting galvanically (that is, producing energy like a battery) to electrolysis (that is, receiving energy), the cathode becomes the anode and vice versa.
电解
电解是当电流通过溶液时溶液中化学物质的分解。电流的化学作用是造成这一过程的原因。
将两个电极放入溶液中并通过开关连接到电池端子。电解池是这种配置的名称。阳极是连接到电池正极端子的电极,而阴极是连接到负极端子的电极。
为了从不纯的样品中提炼和提取金属,使用了电解。这称为电解精炼。它也可用于用另一种金属覆盖一种金属。
电流的化学效应
当电流通过导电溶液时会发生化学反应。这被称为电流的化学效应。以下是电流的一些化学后果:
- 电极上气泡的形成
- 电极上的金属沉积
- 溶液颜色变化
电镀
通过水解将一种金属电镀到另一种金属上,通常是为了避免金属腐蚀或用于装饰目的。电流用于减少溶解的金属阳离子,从而在电极上形成一层薄而连贯的金属涂层,这也是电镀的主要原理。在固体基材上的阴离子的电氧化中,例如在银线上生产氯化银以制造氯化银电极,经常使用电镀。
电镀主要用于改变物体的表面特性(例如,耐腐蚀性、润滑性和耐磨性),但也可用于增加厚度或通过电成型来创建物体。
这就是我们可以构造电镀的方法。电镀是用盐水溶液、电池、电线和鳄鱼夹完成的,鳄鱼夹将碳棒固定在待电镀的金属上,并将金属堆叠在电镀设备中。
例子:
- 使用铜电极和硫酸铜溶液作为电解液 在负极上电镀铜。来自正极的铜离子的添加补充了溶液中的铜。
- 为避免腐蚀或生锈,由铁或钢制成的浴室水龙头采用铬金属电镀。
Types of electrolysis:
- Chromium plating is the process of electroplating chromium onto a metal item.
- Tin plating is the process of electroplating tin onto a metal item.
- Nickel plating is the process of electroplating nickel onto a metal item.
- Silver plating is the process of electroplating silver onto a metal item.
- Gold plating is the process of electroplating gold onto a metal item.
- Copper plating is the process of electroplating copper onto a metal item.
电镀加工
让我们以镀金为例。在这种情况下,将在金属首饰上电镀一层金以增强其外观。
通常,镀金连接到电路的阳极(带正电的电极),而珠宝则保留在阴极(带负电的电极)。两者都沉浸在高度发达的电解棒(溶液)中。在这个阶段,向阳极提供直流电流,氧化金原子并将它们溶解到溶液中。
溶解的金离子在阴极被还原并镀在珠宝上。
影响电镀的因素
电镀受到许多重要元素的影响。这些是其中一些:
- 当前电压电平。
- 浴缸的温度和化学成分。
- 自上次更新以来经过的时间量。
- 阴极和阳极之间的距离是阴极和阳极之间的距离。
电镀的应用
- 为了防止生锈,生锈的金属经常涂上其他金属。
- 镀铬用于浴缸水龙头、汽车保险杠和其他类似物品,以赋予它们明亮、吸引人的外观,同时还能抵抗划痕和磨损。
- 镀银用于餐具和珠宝。
- 锡罐是通过将锡电镀到铁上制成的,用于储存食物。锡是比铁更活泼的金属。因此,食物不会与铁接触,因此可以防止变质。
示例问题
问题一、电镀到底有什么意义?
回答:
Electroplating is the hydrolysis-based plating of one metal onto another, most typically for ornamental purposes or to prevent metal corrosion. Copper plating, silver plating, and chromium plating are examples of specific forms of electroplating. Manufacturers can use low-cost metals like steel or zinc to electroplating.
问题2.写几个电镀的应用。
回答:
Applications of electrolysis are:
- To prevent rusting, rusted metals are frequently coated with other metals.
- Chromium plating is used on bath taps, automobile bumpers, and other similar items to give them a bright, appealing appearance while also resisting scratches and wear.
- Silver plating is used to flatware and jewelry.
- Tin cans are created by electroplating tin onto iron and used to store food. Tin is a more reactive metal than iron. As a result, food does not come into touch with iron and is therefore protected against spoilage.
问题 3. 什么是镀铬,它是如何工作的?铬的哪些特性使其适合电镀?
回答:
The chrome plating process is an electroplating method for depositing a thin layer of chromium onto a substrate (metal or alloy).
Electroplating is accomplished by sending an electric current between two electrodes immersed in a chromic acid electrolyte bath. The substrate to be coated will be one of the electrodes. Chromium atoms are deposited in a layer on the electrode to be plated during the flow of electricity between the two electrodes.
Chromium is a corrosive-resistant metal, but other metals, such as steel, corrode readily when exposed to damp air.
问题四、电镀有什么好处?
回答:
The following are some of the benefits of this method:
1)Corrosion resistance: a corrosion-prone substance, such as iron, can be protected by a coating of non-corrosive material.
2)Decorative items: otherwise dull surfaces can be given a gleam and sheen. This can be used as a decorative piece.
3)Less expensive decorations: instead of utilizing gold or silver, ornaments can be made out of less expensive metals and then electroplated with gold. This significantly lowers the cost of ornaments.
4)Improving mechanical properties: Electroplating can also help metals improve their mechanical properties.
问题5、电镀有什么缺点?
回答:
The following are some of the cons of this method.
- Non-uniform plating: electroplating may or may not be uniform, resulting in a plated material with a poor appearance.
- The technique is both expensive and time-consuming.
- Pollution potential: after usage, the electroplating solution must be disposed of carefully, posing a threat to the environment.
问题六、哪些因素对电镀有影响?
回答:
A number of things have an impact on this procedure. Surface area of the electrodes, temperature, kind of metal and electrolyte utilized, and amplitude of applied current are only a few of these variables.