API-571 Exam Dumps - Corrosion and Materials Professional

According to API RP 571, in the section on "Chloride Stress Corrosion Cracking (Cl-SCC)", several critical factors are outlined that contribute to the initiation and propagation of this mechanism. The document states:

“Critical factors include the presence of chlorides (even at ppm levels), oxygen, elevated temperatures, tensile stress, and susceptible materials such as austenitic stainless steels and some nickel alloys.”

“Oxygen is an accelerant and promotes pitting that can lead to SCC initiation.”

(Reference: API RP 571, 3rd Edition, Section 4.2.2.2)

Therefore, the presence of oxygen is a well-documented critical factor in Cl-SCC. It acts in conjunction with chlorides to initiate localized pitting, which then progresses into cracking. Hence, option B is the correct choice.

API RP 571 describes Temper Embrittlement as:

“A metallurgical degradation mechanism that leads to a reduction in fracture toughness due to long-term exposure in the temperature range of 650°F to 1070°F (345°C to 575°C).”

“It affects Cr-Mo steels and is not easily detected except by impact testing.”

Therefore, option C most accurately defines the condition based on the recognized API description.

API RP 571 and RP 939-C define sulfidation conditions as:

“Sulfidation of iron-based alloys generally becomes significant at temperatures above 500°F (260°C) in hydrocarbon streams with sulfur but without hydrogen.”

“For hydrogen-containing environments, this threshold may be reduced to 450°F (230°C).”

(Reference: API RP 571, Section 4.2.1.1 – Sulfidation; API RP 939-C, Section 3.1)

Therefore, the correct answer is D.

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.

According to API RP 571 Section 5.3.2.3 (Spheroidization):

“Spheroidization is a microstructural degradation that occurs in carbon steels and low alloy steels when exposed to elevated temperatures for long periods, typically beginning at temperatures as low as 650°F (345°C). It involves the transformation of lamellar pearlite into spherical cementite particles, reducing strength and hardness.”

Thus, Option A (650°F / 345°C) is the minimum threshold temperature for spheroidization to begin.

From API RP 571 Section 4.2.3 (Galvanic Corrosion):

“Galvanic corrosion occurs when two dissimilar metals are in electrical contact in the presence of an electrolyte. The more anodic metal corrodes preferentially.”

Contact without insulation and in presence of an electrolyte (like water or brine) is key to galvanic action.

Insulating or coating prevents electrical connection or electrolyte contact, reducing corrosion risk.

Hence, Option D correctly describes the condition that increases galvanic corrosion potential.

API RP 571 on Organic Acid Corrosion in Overheads explains:

“Corrosion caused by organic acids (e.g., formic, acetic) in overhead systems is best mitigated by neutralization, usually via injection of alkaline neutralizing amines that raise pH and reduce acidity.”

“Water wash can be helpful but is often insufficient by itself.”

Therefore, the most effective approach is option C – injection of neutralizer.

As per API RP 571 Section 5.3.2.2 (Sigma Phase Embrittlement):

“Sigma phase embrittlement occurs in austenitic stainless steels (like 300 series) and duplex stainless steels exposed to 1000°F to 1800°F (540°C to 980°C)... This embrittlement results in a significant loss of toughness and ductility.”

Sigma phase is not a concern in Monel (nickel-copper alloy) or 5Cr steels.

400 series are ferritic and not typically affected by sigma phase.

Hence, Option A (300 series stainless steel) is correct.