- Overview: How the API 577 Body of Knowledge Is Organized
- Domain 1: Terms, Definitions, and Acronyms
- Domain 2: Welding Processes
- Domain 3: Welding Materials
- Domain 4: Welding Procedure
- Domain 5: Welder Qualification
- Domain 6: Nondestructive Examination
- Domain 7: Welding Inspection
- Domain 8: Metallurgy
- Domain 9: Refinery and Petrochemical Plant Welding Issues
- Domain 10: Safety Precautions
- Question Format and Exam Mechanics
- Scheduling the Ten Domains Into Your Study Plan
- FAQ
- The API 577 BOK organizes content into exactly ten categories, from terminology to safety precautions.
- The exam is 110 questions (100 scored, 10 unscored pretest) in 195 minutes, closed-book, at Prometric or via ProProctor.
- Passing requires a scaled score of 400 on a 200-500 scale, not a fixed raw percentage.
- Study material is limited to API RP 577 (3rd edition, October 2020) and ASME BPVC Section IX, 2023, Part QW only.
Overview: How the API 577 Body of Knowledge Is Organized
Welding Inspection and Metallurgy Professional (API 577) is an American Petroleum Institute Individual Certification Programs (ICP) credential, and its Body of Knowledge (BOK) is structured around ten defined content areas rather than loose reading assignments. If you are trying to figure out what to actually study - as opposed to what to generically "review" - the ten domains are the map. This guide walks through each one in the order API presents them, with the practical topics candidates most often underestimate.
The current BOK and its associated exam publications are effective December 2025 through August 2027, and the required references are narrow by design: the entire API RP 577, third edition (October 2020), plus ASME BPVC Section IX, 2023 edition, Part QW only. Nothing else is fair game, but nothing inside those two documents is off-limits either - API explicitly states that the whole RP 577 document is subject to testing. For a broader walkthrough of how to build a study plan around this scope, see the API 577 Study Guide 2026: How to Pass on Your First Attempt.
Domain 1: Terms, Definitions, and Acronyms
Terms, Definitions, and Acronyms
This domain tests whether you speak the language of welding inspection precisely. Expect questions that hinge on distinguishing similar-sounding terms rather than calculations.
- Standard welding terminology as defined in API RP 577
- Common acronyms used across welding and NDE documentation
- Precise distinctions (e.g., defect vs. discontinuity, procedure vs. process)
Candidates who skip this domain because it "seems too basic" often lose easy points elsewhere too, since imprecise terminology understanding bleeds into misreading questions in Domains 2 through 10.
Domain 2: Welding Processes
Welding Processes
This is a core technical domain covering how different welding processes work, their advantages, limitations, and typical refinery/petrochemical applications.
- SMAW, GTAW, GMAW, FCAW, SAW fundamentals as covered in RP 577
- Process selection considerations for different joint types and materials
- Common process-related discontinuities
Domain 3: Welding Materials
Welding Materials
Filler metal classification, base metal considerations, and consumable selection are the backbone of this domain.
- Filler metal classification systems and how they map to base metals
- Storage, handling, and control of welding consumables
- Material compatibility issues relevant to refinery service
Domain 4: Welding Procedure
Welding Procedure
This domain leans heavily on ASME BPVC Section IX, Part QW, and expects you to understand how procedures are developed, qualified, and documented.
- WPS and PQR structure, essential variables, and their significance
- Variable classification: essential, nonessential, and supplementary essential
- How procedure qualification links to Welder Qualification (Domain 5)
Domain 5: Welder Qualification
Welder Qualification
Where Domain 4 covers qualifying the procedure, this domain covers qualifying the welder or welding operator performing the work.
- Performance qualification variables and ranges
- Qualification testing methods and acceptance criteria
- Continuity and renewal requirements for welder qualifications
Domain 6: Nondestructive Examination
Nondestructive Examination
NDE knowledge for API 577 focuses on how examination methods relate to welding inspection decisions, not on becoming an NDE Level II in every method.
- Visual, radiographic, ultrasonic, magnetic particle, and liquid penetrant fundamentals
- Selecting appropriate NDE methods for specific weld configurations and defect types
- Interpreting NDE results in the context of acceptance criteria
Domain 7: Welding Inspection
Welding Inspection
This domain is arguably the practical heart of the exam - the day-to-day responsibilities of a welding inspector on a refinery or petrochemical job site.
- Inspection sequencing: before, during, and after welding
- Documentation and traceability requirements
- Common weld discontinuities and how they're identified visually and via NDE
Domain 8: Metallurgy
Metallurgy
Metallurgy is one of the two disciplines named directly in the credential title, and it carries real weight on the exam. This is where many otherwise well-prepared candidates lose points.
- Base metal and weld metal microstructures and how heat input affects them
- Heat-affected zone behavior and hardness considerations
- Preheat, interpass, and post-weld heat treatment fundamentals
- Failure mechanisms tied to welding: cracking mechanisms, embrittlement, and degradation modes
Key Takeaway
If you're deciding where to spend extra review hours beyond the standard pass, put them into Metallurgy and Welding Procedure - they intersect with nearly every other domain and are where RP 577's technical depth is greatest.
Domain 9: Refinery and Petrochemical Plant Welding Issues
Refinery and Petrochemical Plant Welding Issues
This domain applies the fundamentals from earlier domains to the specific operating environment API 577 certificate holders work in.
- Service-related degradation and welding considerations for common refinery equipment
- Repair welding considerations in operating or shutdown environments
- Practical constraints unique to petrochemical plant welding (access, contamination control, hot work permits)
Domain 10: Safety Precautions
Safety Precautions
The final domain covers the safety knowledge expected of anyone supervising or inspecting welding work in a process facility.
- Hot work safety fundamentals and permit-related considerations
- Fume, radiation, and arc-related hazards tied to specific welding processes
- Confined space and general job-site safety awareness relevant to inspection duties
Question Format and Exam Mechanics
Understanding the exam mechanics matters as much as knowing the domains. API's live certification page specifies 110 total questions - 100 scored and 10 unscored pretest items - delivered in 195 minutes. It's a closed-book, computer-based exam: no candidate papers or personal references are allowed. Test centers provide a calculator, scratch paper, and pencil; remote ProProctor sessions provide digital equivalents and require a system-readiness check before you begin.
Most questions are single-answer multiple choice, though API has stated it is gradually introducing alternative item types across its ICP examinations, so don't assume every question will look identical to older practice material. For a full breakdown of the scoring model, see API 577 Passing Score 2026: Exactly What You Need to Pass - the short version is that passing requires a scaled score of 400 on a 200-500 scale, not a fixed percentage of correct answers.
| Exam Element | Detail |
|---|---|
| Total questions | 110 (100 scored + 10 unscored pretest) |
| Time allowed | 195 minutes |
| Format | Closed-book, computer-based, mostly single-answer multiple choice |
| Delivery | Prometric test center or ProProctor remote proctoring |
| Passing standard | Scaled score of 400 on a 200-500 scale |
| References allowed | None - no candidate papers or personal materials |
For an honest assessment of how these mechanics translate into real difficulty, read How Hard Is the API 577 Exam? Complete Difficulty Guide 2026, and check the current pass-rate context in API 577 Pass Rate 2026: What the Data Shows before deciding how much runway to give yourself.
Scheduling the Ten Domains Into Your Study Plan
A generic study calendar won't help you here - what matters is sequencing the ten domains so foundational knowledge builds before you tackle applied topics. A workable structure:
Foundations
- Domain 1: Terms, Definitions, and Acronyms
- Domain 2: Welding Processes
- Domain 3: Welding Materials
Procedures and Qualification
- Domain 4: Welding Procedure (heavy Section IX Part QW review)
- Domain 5: Welder Qualification
Inspection and Metallurgy
- Domain 6: Nondestructive Examination
- Domain 7: Welding Inspection
- Domain 8: Metallurgy - allocate extra time here
Application and Review
- Domain 9: Refinery and Petrochemical Plant Welding Issues
- Domain 10: Safety Precautions
- Full-length timed review across all ten domains
Whether you have eight weeks or less, the sequencing logic stays the same: terminology and process basics first, procedure and qualification next, then the applied domains (inspection, metallurgy, refinery issues, safety) that draw on everything before them. If you need a fast-reference version once you've completed a full pass, bookmark the API 577 Cheat Sheet 2026: One-Page Review of Must-Know Facts for final-week review.
Who These Domains Matter To on the Job
The ten domains aren't academic - they mirror the actual responsibilities employers expect from certificate holders in refineries, petrochemical plants, and engineering firms that support fixed-equipment welding programs. Roles that reference this credential typically involve reviewing WPS/PQR packages, overseeing welder qualification records, coordinating with NDE technicians, and making inspection calls on repair or new-construction welds in process units. If you're evaluating whether pursuing this credential fits your career path, Is the API 577 Certification Worth It? Complete ROI Analysis 2026 and API 577 Jobs both look at how the credential is used in hiring and role differentiation. For the cost side of the decision, including exam and recertification fees, see API 577 Certification Cost 2026: Complete Pricing Breakdown.
Once you've mapped the domains against your own background, running timed practice questions against each of the ten areas individually - not just full mixed exams - is the fastest way to find which domain needs another pass. That domain-by-domain drilling is exactly what a structured practice test platform is built for, letting you isolate weak domains like Metallurgy or Welding Procedure instead of guessing where your knowledge gaps are.
Frequently Asked Questions
API's public materials outline the ten content categories without publishing a fixed percentage breakdown per domain. Rather than trying to guess weighting, prepare each domain to the same depth using RP 577 and ASME Section IX Part QW as your baseline.
Metallurgy and Welding Procedure tend to require the most study time because they involve applied technical reasoning (heat-affected zone behavior, essential variables) rather than straightforward recall, unlike Domain 1's terminology focus.
No. The BOK restricts required study material to API RP 577, third edition (October 2020), and ASME BPVC Section IX, 2023 edition, Part QW only. The exam itself is closed-book with no candidate references permitted.
API's live program page confirms the exam totals 110 questions - 100 scored and 10 unscored pretest - over 195 minutes, but does not publish a per-domain question count breakdown.
Testing windows and application cutoffs change periodically; see API 577 Exam Dates 2026: Testing Windows, Deadlines & Scheduling for the current schedule before you plan your study timeline around the ten domains covered here.
Working through the domains individually - rather than treating "welding inspection" as one undifferentiated topic - is the difference between broad familiarity and exam-ready depth. Pair this domain map with focused practice questions on the main practice test platform and a realistic look at What Is API 577 Certification? if you're still confirming this is the right credential for your role.