100 Questions on Basic Electroplating Knowledge (Part 5)
21.What is electrolysis?
Answer:When the electric current passes through the electrolyte, the redox reaction occurs on the electrode so that the electrolyte is decomposed under the action of the current is called electrolysis. When the electrolyte is energized, the cations move to the cathode, and get electrons at the cathode and be reduced to a new substance; anions move to the anode, and lose electrons at the anode and be oxidized to a new substance. Sometimes the oxidation of the electrode material also occurs at the anode. An example is the electrolysis of molten sodium chloride.
NaCl→Na++Cl-
Cathode Na++e→Na
Anode 2Cl–2e→Cl2↑
Electrolysis industry plays a huge role in the national economy, the smelting of many non-ferrous and rare metals, the preparation of chemical industry products and electroplating, electropolishing, anodic oxidation and so on are realized by electrolysis.
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22.What is electroplating?
Answer: By electrolysis, in the metal parts on the surface of the deposition of a thin layer of other metal methods, it is called electroplating. Plating includes pre-plating treatment (oil removal, rust removal), plated metal layer and post-plating treatment (passivation, dehydrogenation) and other processes. It is used to prevent corrosion of metal products, repair worn parts, increase durability, reflectivity, electrical conductivity and aesthetics. Plating will be metal parts as the cathode, the plated metal plate or bar as the anode, respectively, hanging in the copper pole bar above the electrolyte containing plating components immersed in the direct current.
In individual cases, there are also insoluble anodes, such as chromium plating with lead or lead-antimony alloy anode.
23.What is current strength?
Answer:Current strength, referred to as current, is the amount of electricity passing through the cross-section of the conductor per unit time. The unit is ampere, referred to as ampere (A).
24.What is the current density? How to calculate?
Answer:Current density is the current intensity per unit area of the electrode. Electroplating is a square decimeter as the basic unit of calculation, so the current intensity through a square decimeter of electrode area is called the electrode current density. The cathodic current density is expressed as DK, and the anodic current density is expressed as DA, with the unit of Ampere/square decimeter, i.e., A/d㎡. (Foreign countries also use ampere/square inch expressed). For example, if the total area of the plated piece is 50 square decimeters and the current used is 100 amperes, the current density is 100 amperes ÷ 50 square decimeters = 2 amperes/square decimeters. The cathodic current density has a great influence on the quality of the plating, too high or too low will produce poor quality plating. The current density also directly determines the deposition rate of plating, affecting productivity.
25.What is called current efficiency?
Answer: the current through the plating solution on the cathode of the precipitated metal weight, not necessarily and the law of electrolysis (electrolysis, electrolytic plate on the precipitation or dissolution of the weight of the substance is proportional to the amount of electricity through the current) theoretical calculations of the weight of the weight in line with the general amount of the theory of less than. This is due to the fact that electrolysis does not simply carry out the reduction of metal ions to metal by discharge, but also carries out other side reactions. For example, the precipitation of hydrogen consumes a certain amount of electricity. Therefore, when a certain amount of metal is precipitated, the actual current required is greater than the theoretical calculation. Therefore, the ratio of the current value calculated theoretically and the current value actually required is called current efficiency. The higher the current efficiency, the less power is wasted.
