How to Study API RP 571 Damage Mechanisms for API 510

The scope comes from API's effectivity sheet for September 2026, January 2027 and May 2027 and Body of Knowledge, read on 26 October 2026. Both name RP 571, 3rd edition, March 2020, and both say questions on it come only from Section 2 (terms and definitions) and 15 numbered mechanism paragraphs. If you test in a different window, check that window's sheet, because the list has changed between cycles.

The 15 mechanisms, grouped for study

API lists them in paragraph order. For study, group them by what they look like on a vessel and what the inspector does about them.

Cracking

• 3.3 Amine stress corrosion cracking
• 3.15 Caustic stress corrosion cracking
• 3.17 Chloride stress corrosion cracking
• 3.67 Wet H2S damage (blistering, HIC, SOHIC, SSC)

Thinning at ordinary or moderate temperatures

• 3.8 Atmospheric corrosion
• 3.9 Boiler water and steam condensate corrosion
• 3.14 Caustic corrosion
• 3.22 Corrosion under insulation
• 3.27 Erosion and erosion-corrosion
• 3.37 Hydrochloric acid corrosion

Damage from high temperature service

• 3.35 High-temperature H2/H2S corrosion
• 3.36 High-temperature hydrogen attack
• 3.46 Naphthenic acid corrosion
• 3.61 Sulfidation

Fracture

• 3.11 Brittle fracture

Four, six, four and one is not an even split, but it is the useful one. Within a group, the mechanisms share enough that the exam can ask you to tell them apart. Between groups, the differences are large and rarely tested against each other.

The four-part card

Make one card per mechanism. Read the RP 571 paragraph, then fill in four lines in your own words. Do not copy sentences. Copying is slow and teaches you nothing.

1. What it is. One short sentence.
2. Where it shows up. The service, the part of the vessel, the material. This is the line that gets tested most.
3. What it looks like. Pitting, grooving, even thinning, branching cracks, blisters, a sudden fracture.
4. How it is found. The examination method that fits, and why another method would miss it.

Line 4 ties the mechanism to the NDE side of your preparation. If you need a refresher on the methods, our post on NDE and Section V covers which ones the exam names.

Pairs that get confused

Make a second set of cards, one per pair, with a single line on how to tell them apart. Good pairs to start with:

• Caustic corrosion versus caustic stress corrosion cracking. One thins metal, the other cracks it.
• Amine stress corrosion cracking versus caustic stress corrosion cracking. Both crack welded carbon steel in a chemical service. Know each service.
• Chloride stress corrosion cracking versus the other two. Different materials. Know which one attacks which family of steel.
• High-temperature H2/H2S corrosion versus sulfidation. Both are high temperature thinning in sulfur services, so work out the difference in your own copy.
• High-temperature hydrogen attack versus wet H2S damage. One is a hot hydrogen mechanism and one is a wet sour mechanism. They differ in temperature, in water and in appearance.
• Atmospheric corrosion versus corrosion under insulation. The first is external and open to view. The second hides.

For each pair, ask what a question writer would change to turn one into the other. Usually it is temperature, the presence of water, or the material.

What not to spend time on

RP 571 contains many mechanisms not on the list. They are not named as exam sources. If you are reading RP 571 for general knowledge, that is fine, but do not schedule study hours for it. The same goes for sections of the book that do not matter for a vessel. The scope is a skip list as much as a reading list, which is the idea behind our post on what is not on the API 510 exam.

Section 2 is easy to forget. It has no mechanism, but it has terms, and a closed-book question can turn on a term. Read it once, make cards for terms you did not already know, and move on.

A 10-day plan

Plan on about 30 to 40 minutes a day.

• Day 1: Section 2, plus the grouped list above.
• Days 2 to 3: the cracking group. Two cards each day, four in all, with one pair card at the end.
• Days 4 to 6: the thinning group, six mechanisms across three days.
• Days 7 to 8: the high temperature group and brittle fracture.
• Day 9: the pair cards, then a blind sort. Shuffle all 15 cards, read only the "where it shows up" line, and name the mechanism.
• Day 10: pick a mechanism and write a three-sentence note on how it would change an inspection plan, using what you know about locations, intervals and methods.

Repeat day 9 once a week until the exam. A 10-minute blind sort beats rereading.

Tie mechanisms to the calculations

Several of these mechanisms (atmospheric corrosion, erosion, corrosion under insulation) end in thickness data, and thickness data end in a corrosion rate and remaining life. The exam can give you a scenario, mention a mechanism, then ask for the number. Practice working both sides: name the mechanism, then compute. The corrosion rate calculator is handy for checking arithmetic, and the calculations guide covers the method.

Check what you already know

The free 10-question API 510 check shows how you do on damage mechanisms next to the other Body of Knowledge areas. If you want drills, explanations and a study plan from your exam date, see the plans. The study buddy at /study-assistant can help you work through a mechanism you keep confusing, once you have written your own cards.

FAQ

How many RP 571 damage mechanisms are on the API 510 exam?

The effectivity sheet for September 2026, January 2027 and May 2027 lists 15 mechanism paragraphs plus Section 2, terms and definitions. Check the sheet for your own window, since the list has changed between cycles.

Do I need to read all of API RP 571?

No. API says questions on RP 571 come only from the listed portions. Reading the whole book is not needed for the exam.

Is RP 571 open book or closed book?

RP 571 is among the publications on screen during the open-book part, limited to the sections the sheet lists. API does not say which RP 571 questions fall in which part. Learn the 15 well enough to answer without searching, and keep the paragraph numbers for the rest.

What is the fastest way to remember the mechanisms?

Cards with four lines each, sorted into groups, plus a weekly blind sort. Reading alone does not stick as well as recalling does.

Sources

• API 510 exam publications effectivity sheet, September 2026, January 2027 and May 2027, American Petroleum Institute, RP 571 list, read 26 October 2026
• API 510 Body of Knowledge, September 2026, January 2027 and May 2027, American Petroleum Institute, Section V, page 9, read 26 October 2026