Visual Weld Inspection South Africa: Weld Defects, Quality Checks & Inspection Checklist
Updated: Sep 29
Quick Answer: What Is Visual Weld Inspection?
Visual weld inspection is the systematic examination of a weld and the surrounding fabrication before, during and after welding to identify visible imperfections, verify dimensions and workmanship, and compare the completed work with the requirements that actually apply to the job.
It is not simply asking whether a weld “looks good”.
A proper visual inspection may consider the drawing, joint preparation, fit-up, Welding Procedure Specification (WPS), welding process, consumables, completed weld profile, dimensions, visible imperfections, repair areas and inspection records.
ISO 17637:2016 remains the current international standard specifically addressing visual testing of fusion-welded joints and can also be applied to the joint before welding. ISO
The most important principle is:
A visible imperfection cannot be correctly accepted or rejected until you know which requirement applies.
A smooth weld is not automatically acceptable.
A rough-looking weld is not automatically rejectable.
And a weld that passes visual inspection can still contain internal imperfections that require another examination method.
Visual inspection can tell you — and cannot tell you
Visual inspection can help establish | Visual inspection alone cannot prove |
Weld location and completeness | Complete internal fusion |
Surface cracking or porosity | Absence of subsurface cracking |
Undercut | Absence of internal porosity |
Weld size and profile | Absence of slag inclusions |
Visible root condition where accessible | Internal weld integrity where inaccessible |
Misalignment | Full penetration where the root cannot be viewed |
Distortion | Compliance with every project requirement without the governing documents |
Visible arc strikes and grinding damage | Whether additional NDT is unnecessary |
Visual Weld Inspection South Africa: What Should Actually Be Checked?
Professional weld inspection begins before the first arc is struck.
That matters because some of the most expensive welding failures begin with poor preparation rather than poor bead appearance.
A useful inspection workflow is:
BEFORE WELDING → DURING WELDING → AFTER WELDING → RECORD → DISPOSITION → REINSPECT / ESCALATE
ISO 17637 covers visual examination of welded joints and explicitly allows the principles to be applied before welding as well. ISO
Before welding
Before welding starts, confirm what is supposed to be manufactured.
Check the relevant drawing and WPS, then inspect the material, joint preparation and fit-up.
Important items can include material identity, thickness, bevel geometry, root face, root gap, alignment, cleanliness, tack welds, backing arrangements, accessibility and whether the applicable welding procedure is available.
The purpose is not paperwork for its own sake.
It is to prevent an incorrect joint from being welded correctly.
A technically beautiful weld on the wrong material, wrong preparation or wrong joint is still a problem.
During welding
Inspection during welding can identify conditions that may become hidden beneath later passes.
Depending on the job and inspection responsibility, checks may include process, consumables, shielding gas, polarity, welding position, preheat or interpass controls, pass cleaning, bead placement, root condition, stop-start areas and adherence to the WPS.
The principle is simple:
The cheapest defect to repair is often the one that is identified before another weld pass covers it.
After welding
Once the weld is complete and sufficiently clean for examination, check the completed joint.
This may include weld length, weld size, profile, reinforcement, fillet dimensions, undercut, overlap, visible porosity, cracking, crater condition, misalignment, distortion, arc strikes, root appearance where accessible and adjacent base-metal damage.
A final inspection should also consider repaired areas and whether another NDT method is specified or justified.
The Difference Between a Weld Imperfection and a Weld Defect
This distinction matters enormously.
Weld imperfection
An imperfection is a discontinuity or departure from the ideal geometry or continuity of a weld.
ISO 6520-1:2007 provides the current ISO system for classifying and describing geometric imperfections in fusion welding. ISO confirmed that edition again in 2026. ISO
Examples can include:
cracking;
porosity;
undercut;
overlap;
lack of fusion;
incomplete penetration;
excessive reinforcement;
misalignment.
Weld defect
A defect is not simply “anything that looks wrong”.
Whether an imperfection makes the weld unacceptable depends on the governing acceptance requirements.
ISO 5817:2023 establishes quality levels for specified imperfections in applicable fusion-welded joints in steel, nickel, titanium and their alloys. It identifies quality levels B, C and D, with B corresponding to the highest requirement on the finished weld. ISO
Therefore:
imperfection found ≠ automatic rejection
The inspector must establish:
What is the imperfection?
How large or extensive is it?
Which acceptance requirement applies?
Does it exceed that requirement?
That is a far more professional approach than deciding by appearance.
Common Welding Defects: What They Look Like, Why They Happen and What to Check
This table should become one of the strongest search sections on the entire article.
Weld imperfection | Typical visible clue | Possible contributors | Visual quality check |
Crack | Fine linear indication, branching line, crater split | restraint, hydrogen, poor crater termination, unsuitable procedure | establish location and extent; escalate according to procedure |
Surface porosity | Round holes or pinholes | contamination, moisture, gas problems, wind, shielding loss | record number, size, distribution and location |
Undercut | Groove along weld toe or root | excessive current, fast travel, angle or technique | measure depth, length and continuity |
Overlap | Rolled lip of weld metal at toe | low heat, slow travel, excessive deposition | inspect toe transition and fusion |
Incomplete penetration | Unfused root faces where visible | insufficient root gap, excessive land, low heat, poor positioning | inspect accessible root; do not infer hidden penetration |
Lack of fusion | Unfused edge or surface-connected indication | low heat, contamination, poor angle, poor placement | visible surface clues may require additional NDT |
Excess penetration | Excessive root projection | excessive heat, large root gap, slow travel | measure accessible root profile |
Burn-through | Hole or collapsed root | excessive heat, large gap, thin material | establish extent and repair requirement |
Root concavity | Recessed root surface | heat, insufficient filler, technique or purge issues | measure depth and length where accessible |
Excess reinforcement | Excessively high weld face | too much filler, slow travel, joint geometry | measure height and profile |
Underfill | Weld face below adjacent parent material | insufficient filler, excessive grinding, fast travel | measure depth and extent |
Incorrect fillet size | Leg or throat does not match requirement | incorrect deposition or interpretation | measure with appropriate weld gauge |
Excess convexity | Highly rounded weld profile | slow travel, excessive filler, low voltage | compare geometry to specified requirement |
Excess concavity | Inward fillet profile | high travel speed, insufficient filler | verify effective weld size |
Misalignment | Offset or angular mismatch | poor fit-up, tack failure, dimensional error | measure offset and angular deviation |
Distortion | Bowing, twisting, shrinkage or loss of flatness | heat input, sequence, restraint, weld size | dimensional inspection |
Surface-breaking slag | Dark or irregular trapped material | poor cleaning or bead placement | examine inter-run and finished surface |
Arc strike | Local fused mark outside intended weld | accidental arc contact | record location and follow repair procedure |
Crater defect | Depression, cavity or crack at bead termination | abrupt stop, poor crater filling | inspect all termination areas |
Poor stop-start tie-in | Local build-up, depression, porosity or profile change | poor restart technique | inspect each restart separately |
Grinding damage | Gouges, reduced section or excessive excavation | uncontrolled repair preparation | measure material loss and re-examine repair |
Spatter | Metal droplets around weld | unstable arc or incorrect parameters | assess against project/workmanship requirements |
Possible causes are diagnostic clues — not proof of root cause.
Inspection should identify the condition first. Root-cause analysis may require review of welding parameters, WPS compliance, consumables, equipment, material, technique and production history.
1. Weld Cracks
Cracking demands immediate attention because a crack can propagate beyond what is visible at the surface.
Cracks may occur at the weld centreline, toe, root, crater, heat-affected zone or parent material.
Possible contributors include hydrogen, excessive restraint, unsuitable heat control, hard microstructures, material susceptibility, poor crater termination or an unsuitable welding procedure.
Do not simply grind the visible line away and continue welding.
The full extent and the approved repair procedure need to be established.
Where surface examination cannot define the indication adequately, further NDT may be required.
2. Surface Porosity
Surface porosity appears as rounded cavities or pinholes where gas became trapped during solidification.
It can be isolated, scattered, clustered or concentrated around a stop-start area.
Possible contributors include moisture, oil, rust, paint, damaged gas lines, poor shielding, wind, damp consumables or contaminated material.
The useful visual record is not:
“porosity present.”
Record:
how many
how large
where
how they are distributed
and then compare that condition with the governing requirement.
3. Undercut
Undercut is a groove along the weld toe or root that has not been filled with weld metal.
Possible contributors include excessive current, excessive travel speed, incorrect electrode or torch angle, bead-placement problems or unsuitable manipulation.
Undercut can reduce effective section thickness and create a stress concentration.
The inspection question is therefore not:
“Can I see a little undercut?”
It is:
“What is its depth, length, location and applicable acceptance limit?”
4. Overlap
Overlap occurs where weld metal flows onto the parent material without satisfactory fusion at the edge.
It can resemble a lip or rolled-over weld toe.
Possible contributors include excessive deposition, slow travel, insufficient heat, unsuitable technique or poor positioning.
Do not confuse a smooth-looking large weld with a properly fused weld.
The toe transition matters.
5. Lack of Fusion
Lack of fusion occurs where weld metal does not fuse correctly with the base material or a previous weld pass.
It can occur at the sidewall, root or between passes.
This is one of the best examples of why visual inspection has limits.
Surface-connected lack of fusion may be visible.
Buried lack of fusion may not be.
A beautiful weld cap cannot prove that every internal interface has fused correctly.
6. Incomplete Root Penetration
Incomplete penetration occurs where the weld does not extend through the joint root as required.
Possible contributors include incorrect root opening, excessive root face, insufficient heat, poor access, alignment problems or inappropriate technique.
Where the root is accessible, examine its continuity and profile.
Where it is not accessible:
Do not claim full penetration simply because the face looks good.
That is exactly where inspection discipline matters.
7. Incorrect Fillet-Weld Size
Fillet welds should not be judged by how large they look.
An undersized fillet may not provide the required weld size.
An unnecessarily oversized fillet can increase consumable use, heat input, distortion and production time.
Use the correct gauge and compare the actual geometry with the drawing or applicable requirement.
More weld metal is not automatically more quality.
8. Misalignment and Hi-Lo
Misalignment may be axial, linear, angular or rotational.
Pipe mismatch is often described in workshop language as hi-lo.
Possible contributors include poor fit-up, incorrect component dimensions, ineffective tacking, thermal movement or poor restraint.
Misalignment can affect root access, dimensional accuracy, load transfer and service performance.
Record the actual measurement rather than writing:
“alignment looks okay.”
9. Distortion
Distortion is dimensional change caused by uneven heating and contraction.
It can appear as bowing, twisting, angular movement, buckling, shrinkage or loss of flatness.
The finished weld itself may look excellent while the fabricated component is dimensionally unusable.
Inspection may therefore require:
straightedge, square, level, tape, template, dimensional gauge or other suitable measuring equipment.
Weld quality includes fabrication geometry.
10. Arc Strikes and Grinding Damage
Inspection must extend beyond the weld itself.
An arc strike outside the intended weld area may create local metallurgical or surface concerns.
Uncontrolled grinding can remove defects — but it can also reduce wall thickness, remove required weld metal, create sharp gouges or obscure repair history.
The correct approach is:
identify → record → evaluate → repair under the applicable procedure → reinspect
not:
grind until it disappears.
What Does ISO 17637 Mean for Visual Weld Inspection?
ISO 17637:2016 is the current ISO standard specifically covering visual testing of fusion-welded joints in metallic materials and can also be applied to the joint before welding. ISO
The practical lesson for welders, supervisors and quality personnel is that visual inspection should be systematic.
It needs suitable examination conditions, appropriate access, applicable documents and measuring equipment where required.
Visual testing is therefore a technical process.
It is not:
“Stand back and see whether the bead is straight.”
What Are ISO 5817 Quality Levels B, C and D?
ISO 5817:2023 specifies quality levels for imperfections in applicable fusion-welded joints.
The standard provides three quality levels:
Level | General meaning |
B | Highest requirement |
C | Intermediate requirement |
D | Moderate requirement |
ISO states explicitly that Level B represents the highest requirement on the finished weld. ISO
But this does not mean every weld in South Africa must automatically meet Level B.
The applicable quality level should come from the project requirements, product standard, design, fabrication specification or contract.
Do not invent the acceptance level after welding.
ISO 5817 Does Not Mean Every NDT Indication Uses the Same Acceptance Rule
This distinction is technically important.
The current general ISO standard for selection and application of NDT to welds is ISO 17635:2025.
ISO explains that NDT acceptance levels cannot simply be treated as a direct one-for-one interpretation of ISO 5817 quality levels. Testing method, material, weld thickness, process and quality requirements all influence the examination approach. ISO
That means:
ISO 5817 quality level ≠ automatic UT/RT/MT/PT acceptance rule
Use the correct method-specific requirements.
Visual Weld Inspection Tools
A useful visual inspection kit may include:
inspection light, mirror, magnifier, steel rule, tape measure, straightedge, square, vernier caliper, fillet-weld gauge, bridge-cam style gauge, hi-lo gauge, undercut or depth gauge, camera, temperature equipment where appropriate, approved drawings and inspection forms.
But remember:
A gauge measures geometry. It does not make the engineering decision.
A gauge cannot tell you which code applies.
It cannot identify the WPS.
It cannot decide which acceptance criterion the client specified.
And it cannot detect a buried internal imperfection merely because the dimensions at the surface are correct.
The Visual Weld Inspection Checklist
Before welding
Confirm the drawing, applicable WPS, material, joint type, thickness, preparation, root opening, alignment, cleanliness, tack welds, backing or purge requirements and welding access.
During welding
Confirm the correct process and consumables, appropriate preparation between passes, cleaning, root condition where accessible, stop-start areas and any WPS variables that fall within the inspector's authorised responsibility.
After welding
Check completeness, location, size, profile, visible cracking, porosity, undercut, overlap, root condition where accessible, misalignment, distortion, arc strikes, base-metal damage, repaired areas and required records.
Final disposition
The result should not simply be:
GOOD / BAD
A more useful system is:
ACCEPT
HOLD FOR REVIEW
REPAIR
REINSPECT
REFER FOR ADDITIONAL NDT
The governing procedure determines who has authority to make the final disposition.
When Is Visual Inspection Not Enough?
Visual inspection is extremely valuable because it is fast, relatively economical and can identify many production problems early.
But it only tells you what the examination method is capable of revealing.
The current ISO 17635:2025 framework covers selection of NDT methods according to factors such as quality requirements, material, weld thickness, welding process and extent of testing. ISO
Depending on the job, additional methods may include:
PT — Penetrant Testing
Useful for specified surface-breaking indications on suitable non-porous materials.
MT — Magnetic Particle Testing
Used for surface and near-surface indications in suitable ferromagnetic materials.
UT — Ultrasonic Testing
Used for applicable internal examination using ultrasonic techniques.
RT — Radiographic Testing
Uses radiation-based imaging methods to examine applicable internal weld conditions.
The important point is:
Passing visual inspection does not automatically mean additional required NDT can be skipped.
Can a Weld Look Perfect and Still Be Defective?
Yes.
This is one of the most important lessons for new welders.
A smooth cap with beautiful ripple spacing can still contain internal conditions such as:
lack of fusion, incomplete penetration, internal porosity or slag inclusions.
Conversely, a weld that is not visually beautiful may still satisfy the dimensional and acceptance criteria applicable to the job.
Appearance matters.
But appearance is not the same thing as verified integrity.
That is why professional weld-quality control combines:
procedure + competent welding + inspection + measurement + appropriate NDT + records
rather than Instagram-quality bead appearance.
Can Welders Visually Inspect Their Own Work?
Yes — welders absolutely should learn to recognise obvious problems in their own work.
Welder self-inspection can improve:
joint preparation, bead placement, stop-start control, weld size, cleaning, defect awareness and general workmanship.
But this must not be confused with independent professional inspection or formal NDT personnel certification.
ISO 9712:2021 sets requirements for the qualification and certification of NDT personnel, including visual testing within its defined scope. ISO
In South Africa, SAIW separately offers Visual Testing training and certification pathways under its ISO 9712 NDT certification scheme, including VT Level 1 and Level 2. SAIW
Therefore:
practical welding training ≠ professional welding-inspector certification
and:
being a good welder ≠ automatically being authorised to accept production welds
The required competence and authority depend on the work, employer, specification and inspection system.
Why Weld Defects Keep Reappearing
When the same defect repeatedly returns, repairing the finished weld is treating the symptom.
The underlying issue may exist earlier in the process.
For example:
Repeated problem | Investigate upstream |
Porosity | contamination, shielding gas, consumables, wind, preparation |
Undercut | current, voltage, travel speed, manipulation, bead placement |
Lack of fusion | heat input, travel, joint preparation, angle, cleaning |
Slag inclusion | cleaning, bead profile, access, heat, sequencing |
Distortion | weld size, heat input, restraint, sequence, joint design |
Misalignment | fit-up, tacking, fabrication dimensions |
Excessive reinforcement | filler deposition, speed, joint volume |
Root defects | preparation, root gap, land, alignment, access, technique |
The strongest quality-control system does not only ask:
“Who made the bad weld?”
It asks:
“What in the process allowed this condition to be produced?”
That distinction is crucial for employers.
Visual Weld Inspection for Employers and Fabrication Workshops
For an employer, weld-quality improvement should be treated as a system.
A practical workflow is:
JOB REQUIREMENT
↓
DRAWING / WPS / SPECIFICATION
↓
MATERIAL & FIT-UP
↓
QUALIFIED / SUITABLY SKILLED WELDER
↓
WELDING
↓
VISUAL INSPECTION
↓
ADDITIONAL NDT WHERE REQUIRED
↓
REPAIR / REINSPECTION
↓
TRACEABLE RECORDS
Training can support this system.
It does not replace the system.
If a welding team repeatedly produces undercut, porosity, incorrect weld size or poor fit-up, the answer may be targeted practical development rather than simply issuing another procedure.
Likewise, excellent training cannot compensate for incorrect equipment, unsuitable consumables, bad fit-up, weak supervision or missing quality controls.
How Visual Inspection Helps a Welder Improve Faster
Visual inspection is not only about rejecting work.
Used properly, it creates feedback.
Instead of telling a learner:
“Your weld is bad.”
a stronger training conversation becomes:
The toe has undercut.
The undercut is concentrated here.
Your travel and bead placement changed here.
This is what the corrected profile should look like.
That converts inspection into learning.
A welder who understands defects begins to diagnose their own work instead of simply producing another bead and hoping it is better.
That is one reason defect recognition belongs inside practical welding development.
Visual Weld Inspection in Cape Town: What Should Learners Look For?
A learner interested in weld quality should look for practical training that develops more than the ability to strike an arc.
Useful development areas include:
joint preparation, machine setup, correct consumables, bead placement, welding positions, weld-profile control, fillet-weld dimensions, pipe preparation, defect recognition, distortion control, cleaning, stop-start technique, basic WPS awareness and self-inspection.
The commercial question:
“Which welding course should I book?”
belongs on Swift Skills Academy's welding-programme page rather than being repeated throughout this article.
The purpose of this guide is to teach you what quality looks like — and why.
The Free Visual Weld Inspection Field Pack
The downloadable SSA Visual Weld Inspection Field Checklist & Weld Defect Guide should become a practical working document rather than a promotional brochure.
It should contain:
Weld identification record
Job / project, drawing number, weld number, WPS, material, thickness, welder ID, welding process and inspection date.
Pre-weld inspection
Material, preparation, fit-up, root gap, alignment, cleanliness, tacks, backing, purge and access.
During-weld inspection
Process, consumables, cleaning, root condition, stop-starts, pass condition and observable procedure controls.
Final visual inspection
Cracks, porosity, undercut, overlap, dimensions, profile, root condition, arc strikes, alignment, distortion, grinding damage and repairs.
Defect identification guide
Photographic-style or illustrated reference sections for the most common visible weld imperfections.
Measurement record
Imperfection type, location, measured dimension, permitted requirement, result and comments.
Repair and reinspection register
Defect → repair action → repair reference → reinspection → final status.
NDT escalation
VT only / PT / MT / UT / RT / engineering review / other requirement
Final disposition
ACCEPT
HOLD
REPAIR
REINSPECT
REFER
This can become one of the strongest downloadable welding-quality resources in SSA's entire content library.
Frequently Asked Questions
What is visual weld inspection?
Visual weld inspection is the systematic examination of welding preparation, welding activity and completed welds for visible conditions, geometry, dimensions and workmanship against applicable requirements.
What is the current ISO standard for visual weld inspection?
ISO 17637:2016 remains the current international standard for visual testing of fusion-welded joints. ISO lists it as a confirmed current publication. ISO
What is the current version of ISO 5817?
The current edition is ISO 5817:2023. It provides quality levels for imperfections in applicable fusion-welded joints and identifies Levels B, C and D. ISO
Is ISO 5817 Level B required for every weld?
No. ISO 5817 provides different quality levels. The applicable level should come from the governing design, product standard, project specification or contractual requirement.
What is the difference between an imperfection and a defect?
An imperfection is a departure from ideal weld geometry or continuity. Whether that imperfection makes the weld unacceptable depends on the governing acceptance requirements.
What are the most common visible welding defects?
Common visible conditions include cracking, surface porosity, undercut, overlap, incorrect weld size, excessive reinforcement, underfill, crater defects, arc strikes, misalignment, distortion and poor stop-start areas.
Can visual inspection find lack of fusion?
Surface-connected lack of fusion may sometimes be visible. Internal lack of fusion may not be visible and can require another examination method.
Can a weld pass visual inspection but fail UT or RT?
Yes. Visual testing primarily assesses accessible surface conditions and geometry. Internal imperfections may require other specified NDT methods.
Is visual weld inspection an NDT method?
Visual testing is used within non-destructive testing systems. ISO 17635:2025 includes visual testing within the broader selection and application of NDT methods for welds. ISO
Does welding training qualify somebody as an NDT visual-testing inspector?
No. Practical welding training and formal NDT personnel qualification are separate. ISO 9712 sets qualification and certification requirements for NDT personnel, while SAIW offers Visual Testing certification pathways under its ISO 9712 scheme. ISO
What tools are used for visual weld inspection?
Depending on the work, tools may include suitable lighting, mirrors, magnification, rulers, calipers, straightedges, fillet gauges, hi-lo gauges, bridge-style weld gauges, cameras and inspection records.
Should a welder inspect their own welds?
Yes, self-inspection is an important quality habit. However, it does not replace independent inspection, project-required NDT or authorised acceptance where those are required.
Where can I improve my practical welding skills in Cape Town?
Swift Skills Academy provides practical welding pathways in Cape Town covering several welding processes, progressive skill development, test preparation and employer training. Its commercial welding page should remain the correct destination for programme selection rather than turning this inspection guide into a sales page. Swift Skills Academy
Authoritative Sources & Regulatory References
Authoritative source | What it supports |
International Organization for Standardization — ISO 17637:2016 ISO 17637:2016 official record | Current standard for visual testing of fusion-welded joints |
International Organization for Standardization — ISO 5817:2023 ISO 5817:2023 official record | Current quality levels for applicable fusion-welded joint imperfections |
International Organization for Standardization — ISO 6520-1:2007 ISO 6520-1 official record | Classification and terminology for geometric fusion-welding imperfections |
International Organization for Standardization — ISO 17635:2025 ISO 17635:2025 official record | Current general rules for selection and application of NDT to metallic welds |
International Organization for Standardization — ISO 9712:2021 ISO 9712:2021 official record | Qualification and certification framework for industrial NDT personnel |
South African Institute of Welding — Visual Testing SAIW Visual Testing programme | South African ISO 9712 Visual Testing training/certification context |
Read More
1. Coded Welding South Africa: How to Become a Coded Welder
Natural continuation from weld quality → WPS → qualification testing → coded-welder readiness.
2. Welding Certifications South Africa: Which Certificate Do You Actually Need?
Clarifies the difference between course certificates, occupational qualifications, trade recognition and coded-welder qualification.
3. On-Site Welding Training Cape Town for Employees & Corporate Teams
Moves employer readers from defect identification toward structured workforce development and practical quality improvement. Swift Skills Academy
Final Word
A strong weld is not defined by attractive ripples.
It is defined by whether the joint has been prepared correctly, welded according to the applicable requirements, examined competently and shown to meet the acceptance criteria that actually apply.
That is why visual weld inspection South Africa should never be reduced to:
“Does this weld look good?”
The better questions are:
Was the joint prepared correctly?
Was the correct procedure followed?
What imperfections are visible?
What can be measured?
What does the governing requirement permit?
What cannot visual inspection establish?
Does another NDT method need to be used?
When welders understand those questions, their workmanship improves.
When supervisors understand them, production control improves.
And when employers build them into a proper quality system, weld inspection becomes much more than defect detection.
It becomes defect prevention.
