Q.1 Corrosion of metals is considered as the reverse of extractive metallurgy.
Ans : True
Q.2 What is Corrosion?
A. Conversion of metal atoms to metallic ions
B. Destruction of materials involving in the conversion of metal atoms into metal ions
C. Destruction or deterioration of a material
D. Conversion of metal ions to metal atoms
Ans : Destruction of materials involving in the conversion of metal atoms into metal ions
Q.3 Which of the following materials will undergo Corrosion?
A. Metals and Non-metals
B. Metals, Non-metals, Ceramics, Plastics and Rubbers
C. Metals only
D. Metals, Non-metals, Ceramics and Plastics
Ans : Metals, Non-metals, Ceramics, Plastics and Rubbers
Q.4 The chemical formula of rust is ______.
Ans : Fe2O3
Q.5 Which of the following is an example of wet corrosion?
A. Corrosion of iron in the presence of anhydrous calcium chloride
B. Corrosion due to furnace gases
C. Corrosion of metal in the water
D. Corrosion of titanium in dry chlorine
Ans : Corrosion of metal in the water
Q.6 Corrosion of material by furnace gases is classified as _____.
A. dry corrosion
B. crevice corrosion
C. wet corrosion
D. galvanic corrosion
Ans : dry corrosion
Q.7 Which of the following subjects are important in understanding and controlling corrosion?
B. Material Characterization
D. Both Thermodynamics and Electrochemistry
Ans : Both Thermodynamics and Electrochemistry
Q.8 Corrosion maintenance is vital in _____ industries.
B. both petroleum and paper
D. plastic toy
Ans : both petroleum and paper
Q.9 Which of the following is an incorrect statement?
A. Corrosion is a non-spontaneous process
B. Corrosion is a spontaneous process
C. Corrosion is an irreversible process
D. Corrosion is a degradation process
Ans : Corrosion is a non-spontaneous process
Q.10 Deterioration of paint and rubber by sunlight or chemicals is not a corrosion.
Ans : False
Q.11 Corrosion involves _______ reactions.
B. both oxidation and reduction
Ans : both oxidation and reduction
Q.12 Which of the following is considered as high corrosive resistant material?
A. Cast iron
B. Stainless steel
C. Mild steel
Ans : Stainless steel
Q.13 What is the reason for corrosion?
A. Stability of a metal atom
B. Use of coatings
C. Stability of a metal ion
Ans : Stability of a metal ion
Q.14 Which of the following are necessary in the process of corrosion?
B. Anode, Cathode and Electrolyte
Ans : Anode, Cathode and Electrolyte
Q.15 What are the advantages of corrosion?
A. Zn-carbon electrochemical reactions in the battery
B. Protection of metals by the surficial oxide layer and Zn-carbon electrochemical reactions in the battery
C. Protection of metals by surficial oxide layer
D. Decrease in the strength of material
Ans : Protection of metals by the surficial oxide layer and Zn-carbon electrochemical reactions in the battery
Corrosion and its Classification in Metallurgical Engineering:
1. Definition of Corrosion:
Corrosion is a natural process where metals deteriorate due to their reaction with the environment. It involves the degradation of metals into their constituent compounds, usually oxides or salts.
2. Causes of Corrosion:
– Chemical Reactions: Metals react with substances like oxygen, water, acids, or salts leading to corrosion.
– Electrochemical Processes: Corrosion often involves electrochemical reactions, where metals act as anodes or cathodes.
3. Classification of Corrosion:
– Uniform Corrosion: Occurs evenly across the metal surface. Typically caused by exposure to environmental factors like moisture and air.
– Galvanic Corrosion: Results from the coupling of two dissimilar metals in the presence of an electrolyte. One metal acts as an anode and corrodes, while the other serves as a cathode.
– Pitting Corrosion: Localized corrosion forming small pits on the metal surface. Often caused by chloride ions and can be particularly damaging.
– Crevice Corrosion: Occurs in narrow spaces between metal surfaces. Oxygen concentration and ion concentration variations within crevices lead to corrosion.
– Intergranular Corrosion: Corrosion along grain boundaries in metals. Commonly happens due to impurities in the metal affecting grain boundaries.
– Stress Corrosion Cracking: Corrosion induced by a combination of tensile stress and a corrosive environment. Common in alloys under sustained load in corrosive environments.
– Hydrogen Embrittlement: Caused by the absorption of hydrogen, making the metal brittle. Common in high-strength steels and can lead to catastrophic failure.
4. Prevention and Control:
– Protective Coatings: Applying coatings like paints, enamels, or metal plating to create a barrier against the corrosive environment.
– Corrosion Inhibitors: Adding substances that suppress or slow down the corrosion process.
– Cathodic Protection: Placing a more easily corroded metal (sacrificial anode) in contact with the metal to be protected, ensuring it corrodes instead.
– Material Selection: Choosing corrosion-resistant alloys or materials for specific applications.
– Proper Design: Designing structures to minimize crevices, avoid stress concentrations, and ensure proper drainage.
5. Importance in Metallurgical Engineering:
– Understanding corrosion is crucial for designing durable and reliable metal structures.
– It influences material selection, manufacturing processes, and maintenance strategies.
– Knowledge of corrosion mechanisms aids in the development of corrosion-resistant alloys.