API-571 Exam Dumps : Corrosion and Materials Professional

As per API RP 945 (4th Edition, 2022):

“Post-weld heat treatment (PWHT) is the most effective method for reducing residual stresses that contribute to amine SCC. PWHT minimizes the stress intensity required for crack initiation and growth.”

Lowering temperature helps but is not always feasible.

Water content and amine concentration affect SCC but are not as impactful as PWHT.

Thus, Option A (Post-weld heat treatment) is the most effective mitigation.

According to API RP 571 Section 5.1.2.1 (Hydrogen-Induced Cracking) and Publ 939-A, blistering in carbon and low alloy steels exposed to wet H2S environments can be exacerbated by the presence of cyanides. These accelerate hydrogen entry into steel, increasing the chance of hydrogen blistering.

API RP 571 states:

“HIC and blistering are forms of hydrogen damage that occur in wet H2S environments. The presence of cyanides can significantly increase hydrogen entry and the risk of blistering.”

Publ 939-A (Research on Cracking in Wet H2S Service) also notes:

“Cyanides act as catalytic agents in hydrogen charging, which promotes internal pressure build-up and increases blistering.”

Thus, cyanides (Option B) are the most critical in enhancing blistering in H2S environments.

Dissimilar Metal Cracking (DMC) is a form of high-temperature cracking that frequently occurs in weld joints between carbon steel and austenitic stainless steel (such as Type 316 SS) due to differences in thermal expansion coefficients and mechanical properties.

From API RP 571 Section 5.2.3.1 (Dissimilar Metal Weld Cracking):

“Cracking frequently occurs in weld joints between ferritic and austenitic materials such as carbon steel to 300 series stainless steels due to thermal expansion mismatch during high temperature operation.”

Therefore, Option D (Carbon steel to 316 stainless steel) is the most susceptible combination and the correct answer.