Side by side X4 · CWI vs API 577
CWI or API 577: which welding inspection credential?
API 577 Welding Inspection and Metallurgy is one closed-book exam from the American Petroleum Institute, aimed at refinery and petrochemical inspection. The AWS CWI is three parts, two of them open book, built around welding codes such as D1.1 and API 1104. Pick by the plant and the code you work to.
- Exam
- CWI
- Updated
- October 2026
X4.1Format and rules compared
| Point | AWS CWI | API 577 |
|---|---|---|
| Exams | Three: Part A Fundamentals, Part B Practical, Part C Code Book | One computer-based exam |
| Length | 135 + 120 + 120 or 135 minutes | 3 h 15 min |
| Questions | 165 on Part A (150 scored), 46 on Part B, 50 to 60 scored on Part C | 110, including unscored pretest items |
| Books allowed | None on Part A; the Book of Specifications on Part B; your chosen code on Part C | None; paper and reference materials aren't allowed |
| Eligibility | By education, e.g. high school diploma plus 5 years of welding-related work | API 510, 570 or 653 holders qualify; otherwise BS plus 1 year, 2-year degree plus 2, high school plus 3, or 5 years, within the last 10 years |
| Validity | 3 years at a time, renewed twice before the 9-year recertification | 3 years |
≠ marks a row where the two differ.
Sources: API 577 page, AWS CWI Examination User Guide, September 2026 and the AWS CWI page, checked October 2026. API's own documents differ on the scored count, so we give the total.
X4.2What each one tests
The CWI is about judging welds against a document. Part A covers terms, processes, symbols, visual examination, NDE, metallurgy, calculations and inspector duties. Part B puts gauges and replicas in your hands. Part C makes you find and apply clauses in a code you brought.
API 577 puts metallurgy in its title, and API pitches it to inspectors, welding engineers and metallurgists across the petrochemical industry. On the CWI, base metals, heat treatment and metallurgy get at least 6% of Part A (AWS B5.1:2025, Table 8.1, checked October 2026); the heat control and metallurgy clause covers that slice.
For pipeline inspection inside the AWS system, API 1104 is one of the Part C codes and also a CWI endorsement. NDE shows up on the CWI as a Part A topic and a Part B area, with MT and PT endorsements on top.
Pay is a separate question, and there's no clean public figure for either credential. The US Bureau of Labor Statistics doesn't track welding inspectors on their own; the welding inspector salary page shows the closest BLS numbers with dates.
X4.3Points people mix up
Can I bring the code into the API 577 exam?
No. API states that paper and reference materials aren't allowed (API 577 page, checked October 2026). On the CWI, only Part A runs without books; Parts B and C give you a reference.
How many questions does API 577 score?
API lists 110 questions including unscored pretest items, in 3 h 15 min. Its pages don't agree on the exact split, so check the current exam page before you sit.
Who can sit API 577 without another API certification?
Anyone who meets API's education and experience table: a BS plus 1 year, a 2-year degree plus 2 years, high school plus 3 years, or 5 years with no formal education, all gained within the last 10 years (API 577 page, checked October 2026).
Do I need one before the other?
Neither requires the other. API 577 uses its own eligibility table; the CWI uses AWS's. For the UK-based scheme, see CWI vs CSWIP 3.1.
X4.4Sources
- API 577 page — length, questions, book rule, eligibility, validity (checked October 2026)
- AWS CWI Examination User Guide, September 2026 — parts, times, pass rule (checked October 2026)
- AWS CWI page — eligibility, endorsements (checked October 2026)
- AWS B5.1:2025, Table 8.1 — Part A minimum percentages (checked October 2026)
Going for the CWI?
Our CWI prep app has practice questions for iPhone and iPad. Pair it with the free tags here.