Latest API-571 Practice Questions BY Underwood

Comprehensive and Detailed Explanation From Exact Extract:

Per API RP 571, chloride stress corrosion cracking (Cl-SCC) of austenitic stainless steels is strongly influenced by low pH environments in the presence of chlorides, tensile stress, and elevated temperature.

API RP 571 identifies that:

Chloride SCC can initiate at very low pH levels

pH values near 2 represent a threshold where aggressive chloride attack and cracking become possible

Increasing acidity dramatically increases SCC susceptibility

Therefore, pH = 2 is the lowest and most critical value listed where chloride SCC can begin.

Referenced Documents (Study Basis):

API RP 571 -- Section on Chloride Stress Corrosion Cracking

From API RP 571 on Microbiologically Influenced Corrosion (MIC):

''MIC depends on the presence of water, nutrients, and specific microbial species such as SRB (sulfate-reducing bacteria).''

''While flow velocity may influence deposition and oxygen content, MIC can occur in both stagnant and flowing systems. Hence, it's not strongly dependent on velocity.''

Thus, option D is correct --- MIC is largely independent of flow velocity.