API-571 Exam Dumps - API ICP Programs Questions and Answers

API RP 571 under Cooling Water Corrosion and Scaling:

“Cooling water scaling tends to occur more rapidly as water temperature increases. To minimize scaling, inlet temperatures to exchangers should be kept below 140°F (60°C) where possible.”

“Above this temperature, calcium carbonate and other salts tend to precipitate more readily.”

Thus, option A is correct.

According to API RP 571 Section 5.1.2.6 (Carbonate Stress Corrosion Cracking - CSCC):

“The cracking is usually intergranular and is most commonly detected using wet fluorescent magnetic-particle testing (WFMT) after surface cleaning. PT may not be sensitive enough to detect fine cracks formed by this mechanism.”

Because CSCC cracks are typically surface-connected and very fine, WFMT offers the best visibility, especially after proper surface prep.

Therefore, Option D is correct.

From API RP 571 Section 5.1.1.3 (Amine Corrosion):

“Amine corrosion is a form of general or localized corrosion caused by the presence of amine solutions used to remove acid gases (H₂S and CO₂)... Corrosion is most severe in areas where acid gas loading is high.”

While temperature and concentration are contributing factors, the primary driver is dissolved acid gases such as CO₂ and H₂S.

Thus, the correct answer is Option C.

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.

From API RP 571 Section 5.1.2.5 (Polythionic Acid Stress Corrosion Cracking):

“PTASCC typically occurs on the surface of stainless steels that have been sensitized. Since cracks are open to the surface, liquid penetrant testing (PT) is the most effective detection method.”

Magnetic particle testing is ineffective for non-magnetic materials like austenitic stainless steels.

UT is less effective for fine surface-connected cracks.

Hardness testing is unrelated to detecting cracking.

Thus, Option C (Liquid penetrant testing) is the correct and preferred method for detecting PTASCC.

Comprehensive and Detailed Explanation From Exact Extract:

According to API RP 571, temper embrittlement is a metallurgical condition that affects Cr-Mo low-alloy steels, including 1-1/4 Cr-1/2 Mo, when exposed to temperatures typically in the range of 650 °F to 1100 °F (345 °C to 595 °C) over extended periods. This damage mechanism results in a significant loss of fracture toughness and ductility, particularly at lower temperatures.

API RP 939-C further explains that temper embrittlement does not significantly reduce tensile strength, but it raises the ductile-to-brittle transition temperature (DBTT). As a result, equipment that appears structurally sound may fail catastrophically under sudden loading conditions.

Once ductility is reduced, the material becomes especially vulnerable to rapid temperature changes, which induce high thermal stresses. Thermal shock is therefore a critical secondary damage mechanism. Sudden quenching, cold feed introduction, startup, shutdown, or uneven heating can cause cracking because the embrittled material can no longer accommodate strain plastically.

Option A (Ductile rupture) is incorrect because temper embrittlement promotes brittle fracture, not ductile failure.

Option B (885 °F embrittlement) is incorrect because 885 °F (475 °C) embrittlement primarily affects carbon steels and some stainless steels, not Cr-Mo steels.

Option D (Graphitization) occurs at prolonged exposure above approximately 800 °F (425 °C) in carbon steels and is not the dominant concern for 1-1/4 Cr-1/2 Mo steel in this context.

API RP 571 explicitly emphasizes that embrittled Cr-Mo steels are highly susceptible to cracking during thermal transients, making thermal shock the most likely and dangerous subsequent damage mechanism.

Referenced Documents (Study Basis):

API RP 571 – Section on Temper Embrittlement of Low-Alloy Steels

API RP 939-C – Metallurgical Effects and Service Risks of Temper Embrittlement

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Comprehensive and Detailed Explanation From Exact Extract:

According to API RP 571, surface decarburization is a metallurgical degradation mechanism that occurs when carbon is removed from the surface layers of steel due to exposure to oxidizing environments at elevated temperatures. This results in a carbon-depleted surface layer.

Carbon is a primary strengthening element in carbon and low-alloy steels. When carbon is lost from the surface:

Hardness and tensile strength are reduced

Creep resistance and load-carrying capability decrease

The component becomes more susceptible to plastic deformation and failure under stress

API RP 571 states that decarburization leads to loss of mechanical strength, especially critical in high-temperature service, where components already operate close to material limits.

Why the other options are incorrect:

Option A: Stress cracking is not the primary effect; loss of strength is.

Option C: Decarburization does not directly accelerate oxidation or sulfidation, although both may coexist.

Option D: This is incorrect; decarburization is considered detrimental in high-temperature applications.

Referenced Documents (Study Basis):

API RP 571 – Section on Decarburization and Metal Dusting

API Corrosion and Materials Study Guide

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According to API RP 571 Section 5.3.2.3 (Spheroidization):

“Spheroidization is the transformation of the microstructure of carbon and low alloy steels when exposed to elevated temperatures for long durations. The rate of spheroidization depends on temperature, prior microstructure, and exposure time... The microstructure becomes less effective at carrying loads, and strength is reduced.”

Key influencing factors for the rate of spheroidization are:

Temperature (higher accelerates the process),

Microstructure (initial phase distribution and morphology).

Pressure and hydrogen partial pressure are not relevant for this transformation, nor is stress a primary driver.

Therefore, Option D (temperature and microstructure) is correct.

In API RP 571, Carbonate SCC and Alkaline SCC are both discussed under mechanisms that occur in basic (high pH) environments, often with similar contributing conditions and prevention methods. The document highlights:

“Carbonate SCC is considered a subcategory of alkaline stress corrosion cracking. It results from the concentration of alkaline carbonates under thermal insulation or deposits.”

“Both mechanisms involve the same key parameters: elevated temperatures, tensile stress, and high pH solutions.”

(Reference: API RP 571, 3rd Edition, Section 4.2.2.4 and 4.2.2.3)

Because these mechanisms share similar material susceptibility and operating conditions, they are indeed closely related—option B is therefore the accurate and supported answer.

API RP 571 under Ammonium Chloride Corrosion details:

“The corrosion results from the deposition of ammonium chloride salts from high-temperature process streams as they cool.”

“This typically occurs in crude unit overheads or other systems where salts condense out as the stream temperature drops below their dew point.”

“Corrosion becomes especially aggressive when the salts are wetted by condensation.”

(Reference: API RP 571, Section 4.3.3.1 – Ammonium Chloride Corrosion)

Therefore, option A is technically accurate and supported.