EXPOSE CRACKS AND DISCONTINUITIES IN WELDS BY ETCHING
The macro-etching test is a destructive testing method that reveals the internal structure of welds and base materials. By exposing a polished cross-section to a chemical etchant, the test brings out grain flow, weld profile, penetration depth, and any internal discontinuities such as cracks, porosity, lack of fusion, or overheating conditions.
For welded components, the macro etch weld test is a cornerstone of quality assurance. It confirms whether a weld meets specification requirements before entering service, which is critical for pressure equipment, structural fabrications, and pipework. The macrostructural properties revealed can also be used for welding procedures or personnel qualification.
At Professional Testing Services, we perform macro-etching examination and photography under low magnification on finished products such as weldments and piping. Our accredited metallographic analysis capabilities support fabricators, contractors, and manufacturers across marine, oil & gas, construction, and general manufacturing.
What Is a Macro-Etching Test?
A macro-etching test is a metallographic examination performed at low magnification (typically up to 50×) to evaluate the macrostructure of a metal specimen, which is most commonly a weld cross-section.
The process involves:
- Cutting a representative section from the specimen (usually transverse to the weld)
- Grinding and polishing the cut face to a smooth finish
- Etching the polished face with a chemical reagent to reveal grain structure and weld features
- Visual examination under low magnification, often accompanied by photographic documentation
Unlike micro-etching examination, which examines microstructure at high magnification, macro-etching provides a broader view that is ideal for assessing weld quality, fusion, and overall geometry.
What a Macro-Etch Weld Test Reveals
A macro etch weld test exposes features that are otherwise invisible on a finished weld. Common findings include:
- Weld profile & geometry: bead shape, reinforcement, undercut
- Depth of penetration: full vs partial penetration verification
- Fusion quality: lack of fusion between weld metal and base metal
- Internal discontinuities: cracks, porosity, slag inclusions, gas pockets
- Heat-affected zone (HAZ): extent and characteristics of the HAZ
- Number of weld passes: confirming procedure compliance
- Root and cap conditions: root penetration, cap profile
For fillet welds, the test also verifies leg length, throat thickness, and fusion at the root, which are key requirements under codes like AWS D1.1.
Our Macro-Etching Test Procedure
Our laboratory follows a standardised procedure to ensure consistent results:
Step 1 — Sample Preparation
Specimens are sectioned using precision cutting to avoid heat damage that could alter the microstructure.
Step 2 — Grinding & Polishing
Cut faces are progressively ground and polished to remove machining marks and produce a mirror finish.
Step 3 — Etching
An appropriate chemical etchant is applied based on the material (e.g., nital for carbon steel, oxalic acid for stainless steel). Etching time is controlled to reveal features without over-etching.
Step 4 — Examination & Photography
Etched samples are examined under low magnification. High-resolution photographs are captured and included in the test report for client records and regulatory submissions.
Step 5 — Reporting
A detailed report is issued documenting observations, measurements (penetration, leg length, etc.), and pass/fail assessment against specified acceptance criteria.
Standards We Test To — ASTM E340, ASTM E381 & ASTM A604
We perform macro etching test services to internationally recognised standards:
Standard | Application | ASTM E340 | Standard practice for macroetching of metals and alloys |
|---|---|
ASTM E381 | Standard method of macroetch testing steel bars, billets, blooms, and forgings |
BS EN ISO 17639 | Destructive tests on welds in metallic materials, covering macroscopic and microscopic examination of welds |
We can also perform macro-etching to client-specific procedures or codes such as ASME Section IX, AWS D1.1, ISO 15614, AS 1085.20, AS/NZS 2205.5.1, and API standards.
Macro-Etch Testing for WPS and Welder Qualification
Macro etch weld test is a required destructive test for welding procedure qualification (WPS/PQR) and welder performance qualification under most major codes.
Typical qualification test requirements include:
Test | Purpose | Macro-etch examination | Verify weld profile, fusion, penetration |
|---|---|
Evaluates metallurgical changes across the base metal, HAZ, and weld metal cross-section | |
Confirm weld metal strength | |
Assess weld ductility and soundness | |
Reveal internal discontinuities on fracture surface | |
Impact testing | Verify toughness (where required by code) |
For fillet weld procedure qualification under AWS D1.1, macro-etch examination is specifically required to verify complete fusion at the weld root and to measure leg dimensions.
We also perform grain size analysis where microstructural evaluation is part of the qualification scope.
What to Send Us — Specimen Requirements
At PTS, we strive to provide fast and accurate testing, but we do have requirements. Please provide the following with each submission:
Specimen:
- Welded coupon or component sample large enough to allow cross-sectioning
- Minimum recommended size: sufficient to include full weld and adequate base metal on both sides
- Uncut samples preferred (we perform cutting under controlled conditions)
Documentation:
- Material grade / specification
- Welding procedure (WPS) if available
- Applicable code or standard for testing
- Acceptance criteria (or reference to specification)
- Marking / identification of weld orientation (top, bottom, root)
Contact us before sending if you’re unsure about specimen size or preparation. Our team can advise based on your test requirements.
Macro-etching is a technique used to test a weld by revealing the structure of the base material and weld. It’s a destructive testing procedure that is used to evaluate the characteristics of the weld.
By revealing the large-scale structure of a metallic specimen, it can expose grains for evaluation so the grains can be inspected for size and flow, penetration, cracks as well as overheat conditions.
For welds, etching a cross section may reveal internal discontinuities, weld profile, extent of penetration and the quality of weld. The macro structural properties of a weld can be used for procedure qualification or personnel qualification.
Applications of Macro-Etching Examination
Reveals component defects such as cracks, voids, porosity, and lack of fusion
Verifies weld penetration and profile against specification
Supports WPS, PQR, and welder qualification testing
Provides documentary evidence (photographs) for regulatory and client submissions
Assists in failure analysis and root cause investigations
Reveals component defects such as cracks, voids, porosity, and holes by cutting into metal surfaces
Low magnification microscopes used to examine the finer structure of the weld
Common Test Methods
ASTM E340
ASTM E381
ASTM A604
Industries We Serve
Our macro etching test services support quality assurance and qualification testing across:
- Marine & Offshore — hull welds, structural nodes, deck fittings
- Oil & Gas — pipeline girth welds, pressure vessel welds, process piping
- Construction — structural steel welds, rebar splices
- Manufacturing — fabricated assemblies, forgings, machined components
- Power Generation — boiler tubes, pressure equipment welds
Accredited Testing You Can Submit With Confidence
Our laboratory is accredited to ISO/IEC 17025:2017. Test reports carrying our accreditation mark are accepted by classification societies, regulatory authorities, and end clients across the region.
For more detail on our accreditation scope, see our accreditations.
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Talk to Us Today
Professional testing services have provided clients with superior weld testing services for decades. We run a dedicated weld testing lab, offering the full suite of destructive and non-destructive testing required for qualification and quality assurance.
Our expert testing team can help you with macro-etching examination & photography for your welding samples. If you need a macro etch weld test, call us or send us an enquiry today.
Frequently Asked Questions Macro-Etching Tests
What does a macro-etch test show?
A macro-etching test reveals the internal structure of a weld or base metal at low magnification. It shows weld profile, penetration depth, fusion quality, number of passes, heat-affected zone extent, and internal discontinuities such as cracks, porosity, and lack of fusion. It’s the standard way to visually verify that a weld meets specification.
Is macro-etch testing required for WPS qualification?
Yes, under most welding codes. Macro etch weld test is a required destructive test for welding procedure qualification (WPS/PQR) under ASME Section IX, AWS D1.1, ISO 15614, and similar standards. It verifies that the welding procedure produces welds with acceptable profile, fusion, and freedom from defects.
I need to qualify for a WPS. Which destructive tests are required and where can I get them done?
WPS qualification typically requires: macro-etch examination, tensile testing, guided bend testing, and (where specified) impact and hardness testing. Requirements vary by code, material, and joint configuration. Our laboratory performs all of these tests in-house, so contact us with your WPS details and we’ll advise on the full test scope.
Is a macro etch required for fillet weld procedure qualification?
Yes, under most welding codes. AWS D1.1 requires macro-etch examination of fillet weld procedure qualification test specimens. Similar requirements apply under ASME Section IX, ISO 15614, AS 1085.20, and AS/NZS 2205.5.1. The test verifies complete fusion at the weld root, confirms fusion between weld passes, and allows measurement of leg dimensions and convexity.
Where can I get a procedure specification for macro-etching test coupons?
Test procedures are defined in standards like ASTM E340 (general macroetching), ASTM E381 (steel bars, billets, forgings), and ASTM A604 (remelted steels). For weld coupon testing, procedures follow the governing welding code (ASME IX, AWS D1.1, ISO 15614). Our team can provide guidance on which procedure applies to your samples, so contact us with your material and specification details.
