This set of Corrosion Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Exposure Techniques and its Factors – 1”.
1. Well-planned and executed tests usually result in reproducibility and reliability.
Explanation: Well-planned and executed corrosion tests result in reproducibility and reliability. The test needs to duplicate the actual plant service conditions as closely as possible.
2. Which of the following is/are the types of corrosion testing?
a) Laboratory testing
b) Pilot-plant testing
c) Field testing
d) Laboratory, pilot-plant and field testing
Explanation: Types of corrosion testings:
- Laboratory testing
- Pilot-plant testing
- Actual plant service test
- Field test.
3. Which of the following type of corrosion tests are usually best and more desirable?
a) Laboratory testing
b) Pilot-plant testing
c) Both laboratory and pilot-plant testing
d) Neither laboratory nor pilot-plant testing
Explanation: Pilot-plant tests are usually best and more desirable. It duplicates the intended large-scale operation environment by using the same raw materials, concentrations, temperature, and volume of corrosive solution to the area of metal exposed.
4. Which of the following is/are the purpose of corrosion testings?
a) Evaluation and selection of materials for a specific environment
b) To know the effect on the corrosion of metals by addition of inhibitors
c) To study the mechanism of corrosion
d) Evaluation and selection of materials for a specific environment, to know the effect on the corrosion of metals by addition of inhibitors and to study the mechanism of corrosion
Explanation: Purpose of corrosion testing are:
- Evaluation and selection of materials for a specific environment
- To know the effect of corrosion on metals by the addition of inhibitors
- To study the mechanism of corrosion
- To control the corrosion resistance of metal or corrosiveness of the environment.
5. What is the purpose of the salt-spray test?
a) To evaluate painted surfaces
b) To evaluate electroplated parts
c) To evaluate painted surfaces and electroplated parts
d) Neither to evaluate painted surfaces nor to evaluate electroplated parts
Explanation: Salt-spray test is a type of corrosion testing in which specimen is exposed to seawater or salt water in a box. It is usually used to evaluate painted surfaces and electroplated parts.
6. Which of the following statement is/are true regarding the Huey test?
a) Boiling 65% nitric acid is used as a corrosive solution
b) Used to evaluate the heat treatment of steels
c) Used to evaluate the heat treatment of stainless steels
d) Boiling 65% nitric acid is used as a corrosive solution and used to evaluate the heat treatment of stainless steels
Explanation: The Huey test is used to check the heat treatment of stainless steels. It uses boiling 65% nitric acid as a corrosive solution. Stainless steel is an alloy of iron, carbon, chromium, and nickel.
7. Which of the following specifications of the specimen is must increase the reliability of a corrosion test?
a) Chemical composition
b) Fabrication history
c) Metallurgical history
d) Chemical composition, fabrication history, and metallurgical history
Explanation: Exact chemical composition, fabrication history, and metallurgical history of a specimen are must increase the reliability of a corrosion test. Specimen with 1/16 to ¼ inch thick, 1 inch wide, and 2-inch-long are commonly employed for laboratory testing.
8. A standard surface condition is also desirable and necessary to facilitate comparison with other results.
Explanation: A surface finish of a specimen is one of the factors of corrosion. It is necessary to have a standard surface condition to facilitate comparison with another result. A common and widely used surface finish is produced by polishing with 120 numbered abrasive cloth.
9. Which of the following methods is/are used for the surface preparation of a specimen?
a) Polishing belts
b) Emery papers
c) Electrolytic polishing
d) Polishing belts, emery papers, and electrolytic polishing
Explanation: The surface finish of the specimen is one of the factors of corrosion. Surface preparation of a specimen can be done by using polishing belts, emery papers, and electrolytic polishing.
10. Which of the following type of corrosion testing is depicted in the given figure?
a) Field testing
b) Pilot-plant testing
c) Laboratory testing
d) Both field testing and pilot-plant testing
Explanation: Laboratory testing is one of the classifications of corrosion tastings. It serves as a most useful function as screening tests to determine which materials warrant further investigation.
11. Which of the following is the formula to calculate the minimum testing time for a corrosion test?
a) 2000/milli meters per year
b) 2000/mils per year
c) 1000/millimeters per year
d) 1000/mils per year
Explanation: A rough rule for checking results concerning minimum test time is 2000/mils per year. Here mils are also known as milli inches i.e. 1/1000th of an inch.
2000/mils per year = hours (duration of the test)
12. Which of the following metals is/are subjected to increased attack in the presence of oxygen?
a) Aluminum and its alloys
b) Copper and its alloys
c) Cast iron and steel
d) Copper and its alloys, cast iron and steels
Explanation: Dissolved oxygen will be reduced cathodically into hydroxide ions in many of the corrosion systems and it increases the dissolution of metal anodically. Metals such as copper and its alloys, cast iron and steels are subjected to increase attack in the presence of oxygen.
13. Which of the following metals are resistant to dissolved oxygen?
a) Stainless steels
b) Aluminum and its alloys
c) Stainless steels, aluminum, and its alloys
d) Cooper and its alloys
Explanation: Metals such as aluminum and its alloys, stainless steel is highly resistant to oxygenated corrosive solutions. These metals result in the formation of respective stable oxides.
14. What is liquid-line corrosion?
a) Corrosion on the external surface of a fully-loaded water tank
b) Corrosion at the interface of liquid and gases in a pipeline or tank
c) Preferential corrosion of rivets over sheets in a storage container
d) Corrosion on the external surface of a half-loaded storage tank
Explanation: Liquid-line corrosion is a special type of corrosion that occurs at the interface of liquid and gas in a pipeline or tank. It occurs due to the availability of water vapor and oxygen at the interface along with impurities.
15. Which of the following is/are the cleaning methods after the exposure of specimen?
c) Use of chemical and solvents
d) Sandblasting, rubber-stopper and use of chemical and solvents
Explanation: Cleaning methods after the exposure of specimen:
- Mechanical methods such as scraping, brushing, sandblasting and the rubber stopper
- Chemical methods in which chemical solutions and solvents are used for removal
- Electrolytic methods in which specimen is made cathode under an impressed current.
Sanfoundry Global Education & Learning Series – Corrosion Engineering.
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