This set of Corrosion Engineering Assessment Questions and Answers focuses on “Corrosion Prevention – Coatings – 2”.
1. What is meant by chemical conversion regarding coatings of a metal?
a) Coating metal is vaporized electrically to deposit on the parts to be coated
b) Coatings produced by corroding the metal surface to form an adherent protective layer
c) Hot rolling of two metals together to produce composite sheet
d) A metal wire or powder through the melting flame is blown onto the surface to be protected
Explanation: Chemical conversion is one of the surface coating methods in that coatings are produced by corroding the metal surface to form an adherent protective layer.
2. Which of the following is/are the examples of chemical conversion?
d) Bonderizing, parkerizing, and chromatizing
Explanation: Bonderizing, parkerizing, and chromatizing are examples of chemical conversion. Automobile bodies are best known for phosphatizing treatment. Anodized aluminum with a protective film Al2O3 is another example.
3. In general, coatings should not be used where the environment would rapidly attack the substrate material.
Explanation: In general, coatings should not be used where the environments would rapidly attack the substrate material because one defect or small area of exposed metal would result in rapid degradation.
4. Which of the following is/are the examples of organic coatings?
d) Paints, varnishes and lacquers
Explanation: Organic coatings are widely used to protect more metals on a tonnage basis than other corrosion combating processes. Organic coatings include paints, varnishes, and lacquers.
5. Which of the following is/are factors to consider for organic coatings?
a) Surface preparation only
b) Surface preparation and selection of primary coating
c) Surface preparation and selection of primary and top coatings
d) Selection of primary and top coatings
Explanation: Factors to consider for organic coatings are:
i. Surface preparation usually is done by sandblasting
ii. Selection of primary coatings for strong adhesive bonding
iii. Selection of top coating for appearance and corrosion resistance.
6. What is the purpose of surface preparation?
a) Surface roughening for mechanical bonding
b) Removal of dirt, rust and mill scale
c) Removal of welding flux and other impurities
d) Surface roughening for mechanical bonding, removal of dirt, rust, mill scale, welding flux, and other impurities
Explanation: Surface preparation is a crucial part of the stability of coatings. It roughens the surface to obtain mechanical bonding, removal of dirt, rust, mill scale, welding flux, and other impurities.
7. Which of the following is/are the methods for surface preparation for coating application?
a) Sandblasting and chipping
b) Wire brushing and flame cleaning
c) Sandblasting, chipping, wire brushing and flame cleaning
d) Sandblasting, chipping and flame cleaning
Explanation: Methods for surface preparation for coating application are:
ii. Wire brushing
iii. Flame cleaning
8. Which of the following paints are widely used for corrosion applications?
a) Vinyl and epoxy paints
b) Asphalts and bituminous paints
c) Iron oxide and titanium oxide paints
d) Alkyds and red lead
Explanation: A variety of paints are available in the market for various corrosion applications. It includes asphalts, bituminous paints, red lead, iron oxide, titanium oxide, alkyds, vinyl, and epoxies. Among them, vinyl and epoxies are the class of paints that are widely used for corrosion applications.
9. Which of the following is/are the characteristics of primers or primary coatings?
a) It contains rust-inhibitive pigments only
b) Adequate wettability and short drying time
c) Short drying time, adequate wettability and it contains rust-inhibitive pigments
d) It contains rust-inhibitive pigments and short drying time
Explanation: Characteristics of primary coatings are:
i. It contains rust-inhibitive pigments
ii. Adequate wettability
iii. Short drying time.
10. Which of the following is/are the advantages of coal-tar coatings?
a) Excellent corrosion resistance to fresh and seawater
b) Excellent corrosion resistant to fresh, seawater and soil immersion
c) High abrasive resistance
d) Stable coating
Explanation: Coal-tar coatings are excellent corrosion resistant to fresh, seawater, and soil immersion. Whereas its abrasive resistance and stability of coating are its limitations.
Sanfoundry Global Education & Learning Series – Corrosion Engineering.
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