# Corrosion Engineering Questions and Answers – Prevention – Material Selection and Design – 2

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This set of Corrosion Engineering Questions and Answers for Entrance exams focuses on “Prevention – Material Selection and Design – 2”.

1. Since corrosion is a penetrating action, it is necessary to make allowances for the reduction in thickness in designing pipes and tanks.
a) True
b) False

Explanation: Since corrosion is a penetrating action, it is necessary to make allowances for the reduction in thickness in designing pipes and tanks to meet the mechanical requirements of the service.

2. What should be the approximate thickness of a wall for better performance if the corrosion rate of that wall is estimated as 1/8 inches in 1 year?
a) 1/2 inches
b) 1/8 inches
c) 1/4 inches
d) 1/16 inches

Explanation: The approximate thickness of a wall should be twice that of the estimated corrosion rate to meet the mechanical requirements such as pressure, weight, and stress. Hence, the thickness of the given wall is 2*(1/8) = ¼ inches.

3. Which of the following design of vessels is/are preferred regarding corrosion prevention?

a) Sharp-edged vessel only
b) Curve edged vessel only
c) Both sharp and curve edged vessel
d) Neither sharp nor curve edged vessel

Explanation: Sharp edges components result in the formation of crevices whereas has curve edged components result in proper circulation of solution throughout the component and eliminates crevice corrosion.
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4. Which of the following is/are the design rules for corrosion prevention?
a) Weld rather than riveting containers
b) Design systems for easy replacement of components that fails rapidly
c) Avoid excessive mechanical stress and stress concentration
d) Weld rather than riveting containers, design systems for easy replacements of components that fail rapidly, and avoid excessive mechanical stress and stress concentration

Explanation: Design rules for corrosion preventions:

• Weld rather than the riveting tank and other containers
• Design systems for easy replacements of components that fails rapidly
• Avoid excessive mechanical stress and stress concentration
• Avoid electrical contact between two dissimilar metals.
• 5. Which of the following is the design rule to reduce erosion-corrosion?
a) Avoid excessive mechanical stress
b) Avoid sharp bend in piping systems
c) Avoid sharp bends in piping systems and provide thicker sections to reduce impingement effects
d) Avoid sharp bends in the piping system and excessive mechanical stress

Explanation: Erosion corrosion can be minimized by avoiding sharp bends in the piping system and provide a thicker section to reduce impingement effects. And the better material selection is also one of the factors to prevent erosion-corrosion.

6. Which of the following is not a design rule for corrosion prevention?
a) Riveting the tanks rather than welding
b) Specify operating and maintenance procedures
c) Tank bottoms should be sloped toward drain holes
d) Avoid electrical contact between dissimilar metals

Explanation: Certain design rules can reduce or minimize the effect of corrosion. That includes welding the tanks rather than riveting. This eliminates the formation of crevices at the riveting area and avoids crevice corrosion.

7. Uneven temperature distribution leads to higher corrosion rates and may result in stress-corrosion cracking failure.
a) True
b) False

Explanation: Stress-corrosion cracking is a combination of stress and a corrosive environment. Uneven temperature distribution leads to internal stress and results in stress-corrosion cracking failure.

8. Which of the following is/are included in the general term avoid heterogeneity?
a) Dissimilar metal contact
b) Different phases such as vapor spaces
c) Uneven heat and stress contribution
d) Dissimilar metal contact, different phases such as vapor spaces, and uneven heat and stress distribution.

Explanation: The design rule to avoid heterogeneity includes dissimilar metal contact, different phases such as vapor spaces, and uneven heat and stress distribution.

Sanfoundry Global Education & Learning Series – Corrosion Engineering.