Advertisements
Advertisements
Question
Give preventive methods by giving examples of corrosion?
Solution
Corrosion can be prevented by the following methods:
- Galvanizing: Galvanizing is a process of giving a thin coating of zinc on iron or steel materials to protect them from corrosion. Zinc, being more electropositive than iron, undergoes corrosion first. Thus, it prevents corrosion of iron. However, if zinc layer goes away and the inner iron gets exposed, then the inner iron layer will start to rust.
- Tinning: Tinning is the process of giving a coating of tin over other metals. Cooking vessels, made of copper and brass get a greenish coating due to corrosion. This greenish coating is poisonous. If food is kept in such a vessel, it gets spoiled. Therefore, copper and brass vessels are coated with tin (kalhai) to prevent corrosion.
- Anodizing: The process of coating metals such as aluminium and copper with a thin and strong layer of their oxides by electrolysis is called anodizing process. For this, the copper or aluminium article is used as the anode. As this oxide layer is strong and uniform all over the surface, it is useful for the prevention of the corrosion of the metal.
- Electroplating: Electroplating is the process in which a less reactive metal is coated on a more reactive metal by electrolysis. It protects the object made of reactive metal from corrosion. For example, silver-plated spoons, gold plated ornaments, etc.
- Alloying: The homogenous mixture formed by mixing metal with other metals or nonmetals in a certain proportion is called an alloy Alloying helps to decrease the intensity of corrosion of metals. For example, stainless steel does not get stains with air or water and also does not rust. It is an alloy made from 74% iron, 18% chromium and 8% carbon.
APPEARS IN
RELATED QUESTIONS
Write two methods of preventing the rusting of iron.
Why do we apply paint on iron articles?
Explain why Iron sheets are coated with zinc during galvanization.
Choose the correct answer from the options given below:
Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as
A. Smelting
B. Ore-dressing
C. Calcination
D. Bessemerisation
Why is an iron grill painted frequently?
Name two metals which resist corrosion due to the formation of a thin, hard and impervious layer of oxide on their surface.
Explain why, when a copper object remains in damp air for a considerable time, a green coating is formed on its surface. What is this process known as?
In stainless steel alloy, iron metal is mixed with:
(a) Cu and Cr
(b) Cr and Ni
(c) Cr and Sn
(d) Cu and Ni
No chemical reaction takes place when granules of a rusty-brown solid A are mixed with the powder of another solid B. However, when the mixture is heated, a reaction takes place between its components. One of the products C is a metal and settles down in the molten state while the other product D floats over it. It was observed that the reaction is highly exothermic.
(a) What could the solids A and B be?
(b) What are the products C and D most likely to be?
(c) Write the chemical equation for the reaction between A and B leading to the formation of C and D. Mention the physical states of all the reactants and products in this equation and indicate the heat change which takes place.
(d) What is the special name of such a reaction? State one use of such a reaction.
(e) Name any two types of chemical reactions under which the above reaction can be classified.
Four metals P, Q, R and S are all obtained by the reduction of their oxides with carbon. Metal P is used to form a thin layer over the sheets of metal S to prevent its corrosion. Metal Q is used for electroplating tiffin boxes made of metal S whereas metal R is used in making car batteries. Metals Q and R form an alloy called solder. What are metals P, Q, R and S? How have you arrived at this conclusion?
Mention two uses of the following metals and non-metals
Iron
Name the metal which is a constituent of blood pigment?
Name the metal which is a constituent of plant pigment?
Compare roasting and calcination.
No chemical reaction takes place when granules of a solid, A, are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C, is a metal and settles down in the molten state while the other product, D, floats over it. It was observed that the reaction is highly exothermic.
(i) Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and thermal status of reaction.
(ii) Mention any two types of reactions under which above chemical reaction can be classified.
Answer the following question.
a) What is meant by corrosion?
b) Write names of any two methods of prevention of corrosion.
c) In which method, metal like copper, aluminium are coated with a thin layer of their oxides by means of electrolysis.
d) Explain this method with diagram.
What is done to prevent corrosion of metals?
Give reason.
An iron article should be given a coat of paint
Which of the following method is used to prevent the accumulation of greenish layer on brass due to corrosion?
Corrosion of silver causes a black layer of _______.
When one of the metals in an alloy is mercury the alloy is called _______.
Find the odd one out and give its explanation.
Write the name.
An alloy of copper and tin-
Write scientific reason.
Coins are made from metals and alloys.
Draw a neat labelled diagram.
Electroplating
Observe the following diagram and give answers.
- Name this method of prevention of corrosion.
- For prevention of which metal this method is used?
- What is used as anode in this method?
Observe the following figure and write the answer of the question.
- Which process is shown in the figure?
- Explain the chemical reaction shown in the figure.
- Write the reactions on anode and cathode.
The process of coating the surface of the metal with a thin layer of zinc is called ______
What is rust?
Copper objects lose their shine and form green coating of ____________.
The diagram shows the reaction between metal and dil. acid.
What is the reason for different behaviour of Mg in test tube B?
The table shown below gives information about four substances: A, B, C and D.
| SUBSTANCE | MELTING POINT (K) | ELECTRICAL CONDUCTIVITY | |
| SOLID | LIQUID/ AQUEOUS | ||
| A | 295 | Good | Good |
| B | 1210 | Poor | Good |
| C | 1890 | Poor | Good |
| D | 1160 | Poor | Poor |
Identify Ionic compounds from the above given substances.
Identify the correct statement from the following:
Give an example of a chemical reaction for each of the following situations:
Sound is produced
Give scientific reasons.
Silver amalgam is used for filling dental cavities.
Explain the chemical reactions in rusting of iron.
