Basically in the silver plating method, the silver bar acts as the anode, the object is to be plated acts as the cathode and the double cyanide of potassium and silver acts as the electrolyte. When the direct electric current is passed between the anode and the cathode, the positive silver ions (Ag+) from the double cyanide of silver and potassium solution to the negative anode (the object), where they are neutralized by the electrons and stick to the object as silver metal.
For cadium plating electrolyte used is
The cadmium plating electrolyte contains the sodium cyanide and a cadmium salt in the presence of another alkali compound, such as caustic soda or sodium carbonate. Usually the cadmium plating electrolyte has added with the following ratio of the sodium cyanide, cadmium and caustic soda. That is 30 grams of cadmium cyanide, 50 grams of sodium cyanide and 20 grams of caustic soda per liter of electrolyte solution.
Which of following is invariably seen in an electroplating plant?
In an electroplating plant, the DC power supply is used to do the electroplating operation. So, we can use DC generator (or) rectifier to get DC power supply from the conventional AC power supply. But, if we use the DC generator, the conversion efficiency is less and maintenance and initial cost is more. That’s why most of the electroplating plant has the rectifier and we can invariably see it which is used to convert AC power supply into DC power supply.
Electrics supply for electroplating should be
In an electroplating process, when the more electrons flow into the piece, the metal particles in the object are removed from it. This operation happens by giving the positive direction of the power supply through the anode and cathode plates. Then, when the electrons are removed from the piece, the dissolved metal particle in the electrolyte sticks into the working piece. This operation happens by giving the negative direction of the power supply through the anode and cathode plates. Thus, we need the constant single direction power supply at a time to do the above two operation. That is why the DC power supply used in electroplating applications.
Which law(s) find application in electrolysis?
The ohm’s law is used in resistance circuits. The gauss’s law and coulomb’s law are used to find the electric field due to line charge. There are two different laws of faraday’s law that uses in electrolysis process. The first law states that the amount of chemical change produced by an electric current in the electrode or electrolyte is directly proportional to the electricity used. The second law states that the amount of chemical changes produced by the same quantity of electricity in different substances is proportional to their equivalent weights.
Silver coating is provided for
Silver coating resists the corrosion affections in ferrite metals. So, it is used for protective purpose. The silver coating shows the clear and shiny at its outside surface. So, it is used for decorative purpose. The work piece surface is very smooth after finishing the coating. If we used this kind of surfaces in bearing application, the friction is very less. So, it is also used for bearing surfaces.
Current efficiency in electroplating is usually
The electric current efficiency is the ratio of the weight actually deposited and the weight to be expected from Faraday's laws. In the electroplating process, according to this statement the loss of efficiency is less because the input electric current does the electroplating process effectively without too much loss. It can maintain the electric current efficiency between 90 to 98 %.
Aluminium is produced from bauxite by
The mined bauxite is refined into alumina (Al2O3), and then it is converted into the metallic aluminium (Al) by electrolytic process. In this process, the purified aluminium oxide is continuously fed into the tray. The mineral cryolite (Na3AlF6 - Sodium hexa - fluoro - aluminate) is added at 500°C melting point and when the electric supply is passed between the positive and negative carbon tube, it dissolves the purified ore into Al3+ and O2– ions. Finally the molten aluminium is deposited at bottom of the tray and then it can be collected.
Galvanizing is the coating of
The zinc is the only metal that basically to save the integrity of the iron from the corrosion effects for a longer period of time. That is why the zinc is coated in the surface of iron using galvanization process.
Coating generally recommended for hard surfacing is
Basically chromium plating is widely used in industrial based tools like. There is no necessity of soft surfacing. The surface should be very hard for achieving the capability to do work for this kind of heavy tools in industries. This plating is also called as hard chrome plating.
Basically the chromium plating is the hard surface plating. For that, we need to generate the greater temperature to achieve the surface of the object as hard. So, it requires the highest electric current density such as 325 Amps / feet2 or 35 Amps / m2.
Electro-chemical equivalent is usually expressed in
As per the Faraday’s first law of electrolysis, the electro - chemical equivalent is the ratio of mass of chemical deposition to the quantity of electricity. We know that, the unit mass of chemical deposition is grams and the unit of quantity of electricity is coulomb. So, the unit of electro - chemical equivalent is milli - gram per coulomb.
During electroplating the weight of substance deposited depends on
According to the Faraday’s first law of electrolysis, the mass of the chemical deposition due to flow of electric current through an electrolyte is directly proportional to the quantity of electricity passed through it. So, the weight of the chemical deposition depends on the quantity of electricity.
Zinc cadmium and lead coating is generally provided for
The zinc, cadmium and lead are the anodic to iron and its corrosion rate is very less. It provides relatively long term protection for the cast irons from the corrosion. So, these coatings are generally provided for corrosion.
Which of the following substance when added to electrolyte promotes smooth deposition?
The above substances are smooth in nature. During the electroplating process, the high electric current density is too high. Thus, there is a chance of forming the hard surface. So, when the substances are added to the electrolyte solution, it promotes the smooth deposition.
Addition of which of the following substance in electrolyte helps in producing bright finish ?
These three materials are used to remove the waste particles after finishing the electroplating process by feeding the object into those solutions. Hence, finally it produces the bright finish.
During electroplating the amounts of different substances liberated by same quantity of electricity are proportional to their
According to the Faraday’s second law, the amounts of different substances liberated by the same quantity of electricity are proportional to their chemical equivalent weights.
The melting point of silver metal is less than the other above shown materials. If the electric current density is very high, then the temperature generation in the electrolyte is also too high. So, it is not suitable for silver. That’s why the lowest electric current density is generally recommended for the silver plating.
Energy efficiency during electroplating is usually in the range
The energy efficiency is usually very less in the range of 50 to 80% because the in electroplating process, other reactions are started such as the evolution of hydrogen when the applied voltage is increases which eventually reduces the overall system’s energy efficiency.
Which metal is deposited for electro forming?
In the basic electroforming process, an electrolytic bath is used to deposit nickel or other electro - formable metals like copper, silver or chromium onto a conductive patterned surface such as stainless steel and iron.