API-571 Exam Questions Instant Access - No Installation Required

Question 1

The potential for galvanic corrosion will increase when:

Ainsulating dissimilar metals with different electro-chemical potentials.

Busing a relatively large volume of anodic material.

Capplying a coating to both metals.

Ddifferent metals are in contact with presence of electrolyte.

Answer : D

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.

Question 2

Cooling water corrosion of exchanger tubes is typically increased by:

AIncreasing the passivation layer.

BDecreasing the process temperature.

CIncreasing the oxygen content.

DDecreasing the cooling water outlet temperature.

Answer : C

According to API RP 571, under the section 'Corrosion in Aqueous Environments -- Cooling Water Corrosion', one of the key contributors to corrosion in carbon steel and other materials used in heat exchangers is the presence of dissolved oxygen. API RP 571 states:

'Oxygen is a primary contributor to corrosion in cooling water systems. Systems open to the atmosphere are typically more corrosive than closed systems due to the continual replenishment of oxygen.'

'Corrosion rates are highest where oxygen concentration is the greatest, especially in systems using untreated or poorly treated water.'

'Carbon steel corrodes in the presence of oxygen and water, forming corrosion products that may or may not adhere to the surface.'

(Reference: API RP 571, Section 4.3.1.1 -- Cooling Water Corrosion)

Therefore, increasing oxygen content directly increases corrosion activity in exchanger tubes, making option C the correct and documented answer.

Question 3

What is the best way to inspect for brittle fracture?

AWet fluorescent magnetic-particle testing

BTensile testing

CUltrasonic examination

DThere is no effective way

Answer : A

API RP 571 notes that for detecting existing cracks or flaws that may lead to brittle fracture, especially those that initiate at welds or surface stress points:

''Wet fluorescent magnetic-particle inspection is highly effective for detecting surface-breaking flaws in ferromagnetic materials that are susceptible to brittle fracture.''

''It is sensitive to tight cracks and surface discontinuities that may serve as initiation sites for brittle fracture.''

(Reference: API RP 571, Section 4.2.1.2 -- Brittle Fracture)

Therefore, option A is correct as it is the most effective NDE technique for detecting early signs of brittle cracking.

Question 4

Phosphoric acid corrosion in polymerization units is usually found under what circumstances?

ATurbulent flows

BLow velocity areas

CTwo-phase flow

DWhen the acid dries out

Answer : D

API RP 571 states under the section Phosphoric Acid Corrosion:

''Corrosion usually occurs when the acid dries out and forms concentrated phosphoric acid deposits, which are very aggressive to carbon steel.''

''Drying or concentration occurs due to poor flow distribution or operational upsets. Localized areas may experience acid concentration due to vaporization.''

(Reference: API RP 571, Section 4.3.3.8 -- Phosphoric Acid Corrosion)

Therefore, the most aggressive corrosion occurs when the acid dries out, making option D correct.

Question 5

Metal dusting usually occurs in the operating temperature range of:

A600F--1200F (315C--650C)

B900F--1500F (480C--815C)

C1200F--1800F (650C--980C)

D1500F--2100F (815C--1150C)

Answer : A

As per API RP 571 Section 5.1.4.2 (Metal Dusting):

''Metal dusting is a type of carburization attack that typically occurs in high carbon activity environments, with temperatures generally between 900F and 1200F (480C to 650C), although damage has been reported as low as 600F (315C).''

Therefore, the commonly accepted operational range is best described by Option A: 600F--1200F (315C--650C).

Question 6

Polythionic acid stress corrosion cracking is:

AIdentified by transgranular cracking on the process side of equipment and piping.

BFound only in low carbon grades of austenitic stainless steel.

CTypically localized and may not be evident until a leak appears.

DRarely found in process furnaces.

Answer : C

API RP 571 under Polythionic Acid Stress Corrosion Cracking (PTA SCC) specifies:

''Cracking is usually intergranular, and often localized, especially in sensitized austenitic stainless steels exposed to sulfur-containing environments during shutdown or cleaning.''

''It is not always visible on inspection and may only become evident when a leak occurs.''

(Reference: API RP 571, Section 4.2.2.5 -- PTA SCC)

Hence, option C is correct as it best describes the detection difficulty and behavior of PTA SCC.

Question 7

Blistering and hydrogen-induced cracking (HIC) damage are most affected by what aspect of steels?

AInclusions

BHardness

CResidual Stress

DPermeability

Answer : A

API RP 571 discusses Hydrogen-Induced Cracking (HIC) and Blistering under the section:

''HIC and blistering are most strongly influenced by non-metallic inclusions, particularly elongated manganese sulfide (MnS) inclusions, which serve as trap sites for hydrogen atoms.''

''These inclusions create local planes of weakness where atomic hydrogen recombines into molecular hydrogen (H), causing high pressure and cracking.''

(Reference: API RP 571, Section 4.2.2.7 -- Hydrogen Blistering and HIC)

Thus, inclusions are the critical material factor, making option A correct.

API Corrosion and Materials API-571 Exam Questions