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Multiple Choice Questions on Forms of Corrosion |
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| Questions 16 - 20 |
Page 4 of 4 |
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16. |
Which one of the following is the most practical method of preventing pitting? |
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By substituting a very expensive material, such as copper |
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Removing all oxidizing ions from the solution |
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Adding strong inhibitor to completely suppress corrosion |
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flushing nitrogen in the system to eliminate oxygen |
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17. |
Knife-line attack occurs on stabilized grades of steels, because |
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the metal has not been heated to a temperature high enough to dissolve the stabilizing carbide |
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the steel was cooled too fast to precipitate the chromium carbide |
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the steel was cooled too fast to precipitate the stabilizing carbide |
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the metal was heated to a temperature at which the stabilizing elements dissolve in the chromium |
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18. |
Electric arc welding is preferred over gas welding of stainless steels, because |
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it is faster and hence cheaper |
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post-weld annealing is never needed |
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high intense heat of arc welding minimizes sensitization |
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welders who can weld stainless steels are hard to find |
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19. |
The most generally accepted theory of crack propagation during stress corrosion cracking is |
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corrosion only initiates the crack and propagation is purely by mechanical stressing |
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corrosion not only initiates the cracks but causes the propagation in combination with the effects of mechanical stress |
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it is always a result of diffusion of hydrogen |
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the crack propagation is purely a mechanical phenomena independent of corrosion |
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20. |
Generally speaking, the time required for stress corrosion cracking failure |
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increases with the amount of corrosion |
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decrease with increasing tensile stress |
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depends on the strength of material |
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the decrease in time is directly related to the applied residual and thermal stresses |
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