How the quiz works
Each set serves all 18 questions in a shuffled order, with the options shuffled too. Most questions describe a vessel or line in service and ask which mechanism fits. The rest ask which material is at risk, which change resists the mechanism, or where to look and which method finds it. Check your answer and you get the reason the right option is right, why each of the other three is wrong, and the RP 571 paragraph to open.
You score one point per question. At the end you see your score by the four things RP 571 sets out for every mechanism: Appearance: what the damage looks like; Affected materials; Critical factors: the service that drives it; Inspection: where to look and which method fits. You also get the list of paragraphs behind the questions you missed, so you know exactly which pages to re-read. Hit New shuffle for a fresh order, and quote the set number if you report an error.
Read-the-clues checklist
Run these in order on any damage mechanism question. Most stems give away the answer by the third clue.
- Material. Carbon or low-alloy steel, or 300 series stainless? Chloride cracking needs the stainless; amine, caustic and wet H2S cracking are carbon steel problems.
- Hot or cool. Sulfidation, high-temperature H2/H2S corrosion, hydrogen attack and naphthenic acid corrosion need high temperature. Wet H2S damage, HCl corrosion and atmospheric corrosion need liquid water.
- What is in the stream. Hydrogen, H2S, chlorides, caustic, amine, crude acids, oxygen in water, or sand. One word in the stem often settles it.
- Thinning, cracking or a sudden break. Wall loss, a crack network and a split during a cold test point to different families.
- Where it sits. An as-welded joint, the area opposite an inlet, the first condensation point, a low spot under insulation or a hard weld repair each point to a short list.
- Then the method. Thinning calls for visual examination and UT thickness readings or scans. Surface cracks call for wet fluorescent magnetic particle or penetrant testing. Internal damage calls for straight-beam or specialized UT.
Worked examples
Example 1: amine or caustic cracking at an as-welded joint?
The stem: a carbon steel vessel, welds never stress relieved, fine cracks beside a weld, and the vessel holds lean amine. Step 1: material is carbon steel, so chloride cracking is out. Step 2: the damage is cracking at an as-welded joint, which narrows it to the two stress corrosion cracking mechanisms that need residual weld stress, amine (3.3) and caustic (3.15). Step 3: the stream decides it. Lean amine means amine stress corrosion cracking, 3.3. Swap the amine for a steam-traced caustic line and the same cracks become caustic SCC, 3.15. Both are prevented the same way, by postweld heat treatment, which is why the fluid is the clue that matters.
Example 2: blisters and stepped cracks, or a plate flaw?
The stem: carbon steel plate in wet sour water, bulges on the inside surface, and straight-beam UT shows flat indications at mid-wall joined by short steps, away from any weld. Step 1: carbon steel, water and H2S together point to wet H2S damage, 3.67. Step 2: pick the form. Bulges are blisters, and flat cracks linked in steps are hydrogen-induced cracking. Neither needs applied stress. Step 3: rule out the look-alikes. SOHIC stacks cracks through the thickness next to a weld; sulfide stress cracking needs hard weld metal; a lamination is a single flat flaw from the mill that does not raise blisters or grow steps in service. The answer is blistering and HIC under 3.67. Wall readings from the same scan feed straight into the corrosion rate calculator when the damage is thinning instead.
To see where RP 571 sits among the other references on the exam, read the API 510 Body of Knowledge guide. For the editions and section limits of every publication, see the effectivity sheet guide.
Damage mechanism quiz FAQ
Which damage mechanisms are on the API 510 exam?
The API 510 effectivity sheet for the September 2026, January 2027 and May 2027 windows lists API RP 571, 3rd edition: Section 2 (terms and definitions) plus 15 mechanism paragraphs, from 3.3 amine stress corrosion cracking to 3.67 wet H2S damage. The Body of Knowledge for the same windows lists the same 15. This quiz covers all 15 and nothing else, so you are not studying mechanisms that cannot come up.
Do I need to memorize the temperature ranges for every mechanism?
Learn the pattern first: which material, which fluid, hot or cool, thinning or cracking, and where on the vessel. That pattern is what lets you name a mechanism from a short description. Then add the limits RP 571 gives for each paragraph from your own copy. This quiz leaves those numbers out on purpose, so it never copies them from the book.
How do I tell sulfidation from high-temperature H2/H2S corrosion?
Look for hydrogen. Both thin hot carbon and low-alloy steel under a sulfide scale, but sulfidation (3.61) is the case without hydrogen, as in crude unit hot sections, and high-temperature H2/H2S corrosion (3.35) needs hydrogen in the stream, as in hydroprocessing reactor effluent. More chromium helps against sulfidation, and helps less once hydrogen is present.