API-571 Exam - Topic 1 Question 111 Discussion

Actual exam question for API's API-571 exam

Question #: 111
Topic #: 1

A carbon steel bundle from the overhead condenser in the crude unit operates at 300 F and is in hydrochloric acid service. It showed severe pitting type corrosion when pulled for inspection. What type of material would be best suited for this service?

A5Cr-0.5Mo

B316 stainless steel

C9Cr-1Mo

DTitanium

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Suggested Answer: D

by Carlene at Jun 14, 2025, 02:17 PM

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Nobuko

5 months ago

Not sure if 316 is enough for severe pitting, though.

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Hortencia

5 months ago

Definitely agree with 316 stainless steel for hydrochloric acid service.

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Kent

6 months ago

I think 9Cr-1Mo could handle the heat better.

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Tabetha

6 months ago

Titanium? Really? That seems overkill for this situation.

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Dorsey

6 months ago

316 stainless steel is known for its corrosion resistance in acidic environments.

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India

6 months ago

I recall that 5Cr-0.5Mo is often used for high-temperature applications, but I’m not sure how it performs in hydrochloric acid. I think stainless steel is safer.

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Leontine

6 months ago

I feel like we had a similar question in practice about materials in acidic service. I think 9Cr-1Mo was mentioned as a potential candidate, but I’m not confident.

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Nu

7 months ago

I'm not entirely sure, but I think titanium could handle the corrosion better than the others. It’s more resistant, right?

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Hollis

7 months ago

I remember we discussed that carbon steel isn't great in acidic environments, especially hydrochloric acid. I think 316 stainless steel might be a good option here.

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Ilda

7 months ago

I'm a bit unsure about the 5Cr-0.5Mo and 9Cr-1Mo options. I'll need to research their corrosion resistance in hydrochloric acid service to make a confident decision.

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Pearly

7 months ago

Titanium could be a good choice here, but it might be overkill and more expensive than necessary. I'll have to weigh the pros and cons.

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Yvonne

7 months ago

Okay, I know pitting corrosion is a major issue in acidic environments. I'm leaning towards 316 stainless steel since it has good corrosion resistance.

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Leeann

8 months ago

Hmm, this seems like a tricky one. I'll need to think carefully about the corrosion resistance properties of each material option.

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Eric

10 months ago

Hold on, did someone say 'overhead condenser'? I bet the engineers were just daydreaming about their next vacation when they designed this thing. Better bring a snorkel for that acid shower!

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Elenora

10 months ago

Hmm, I'm not sure 5Cr-0.5Mo would be robust enough for this service. Seems like it might be a bit too lightweight for the job. Time to beef up the alloy content!

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Berry

9 months ago

User 2

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Burma

9 months ago

User 1

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Hailey

9 months ago

User 2: Yeah, I agree. It's important to have a material that can withstand the harsh conditions.

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Twila

10 months ago

User 1: I think 9Cr-1Mo would be a better choice for this service.

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Belen

10 months ago

I'm going with 316 stainless steel. It's a classic choice for corrosive services and should hold up well to the pitting issues. Just hope the cost doesn't blow the budget!

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Danilo

9 months ago

User 2: Agreed, it's a reliable option for corrosive environments.

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Santos

10 months ago

User 1: I think 316 stainless steel is a good choice for this.

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Carey

10 months ago

Titanium is a great option here. It's highly resistant to pitting and crevice corrosion, even in aggressive acid environments. Plus, it's lightweight and easy to fabricate.

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Mona

9 months ago

A: It's also lightweight and easy to work with, which is a bonus.

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Alise

10 months ago

B: Yeah, titanium is known for its resistance to corrosion in acid environments.

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Ceola

10 months ago

A: I think titanium would be the best choice for this service.

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Pete

11 months ago

Why do you think 9Cr-1Mo is better?

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Theodora

11 months ago

I think 9Cr-1Mo would be the best choice for this application. The high chromium content provides good corrosion resistance in hydrochloric acid, and the molybdenum addition further enhances the corrosion protection.

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