API 653 Material Evaluation 3

Question 1

Which type of corrosion produces a smooth, uniformly thinned surface and is generally easier to evaluate than localized corrosion?

Accepted Answer

General (uniform) corrosion

Answer

General corrosion thins the plate uniformly, making thickness measurements straightforward and corrosion rate projections more reliable.

Question 2

When a tank inspector discovers stress corrosion cracking (SCC) on a stainless steel shell, what is the most critical environmental factor to investigate?

Accepted Answer

Chloride ion concentration

Answer

Chloride ions are the primary environmental trigger for stress corrosion cracking in austenitic stainless steels.

Question 3

API 653 requires that shell repair welds be made using a minimum preheat temperature based on the:

Accepted Answer

Shell plate thickness and carbon equivalent

Answer

Preheat requirements for repair welding are determined by the base metal's carbon equivalent and the plate thickness per API 653 welding provisions.

Question 4

A tank bottom plate exhibits a reddish-brown scale with deep pitting beneath it. This morphology is most characteristic of:

Accepted Answer

Microbiologically influenced corrosion (MIC)

Answer

MIC produces localized pitting under biological deposits (tubercles) that often appear as reddish-brown mounds on the plate surface.

Question 5

For a tank bottom, API 653 specifies the minimum thickness for fitness-for-service based primarily on:

Accepted Answer

Hydrostatic pressure from liquid head above the bottom

Answer

Tank bottom minimum thickness per API 653 is set at 0.10 inches (2.5 mm) but is also governed by the ability to resist hydrostatic head from the stored liquid.

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

API 653 Material Evaluation 3