Article 6 of ASME Section V governs liquid penetrant examination (PT) for surface-breaking discontinuities in nonporous metallic and nonmetallic materials. PT is the workhorse surface NDE method for aluminum, stainless steel, and other non-ferromagnetic materials where magnetic particle (Article 7) cannot be applied. Article 6 covers visible (dye) PT and fluorescent PT, with the choice of penetrant removal — water-washable (Type B), solvent-removable (Type C), and post-emulsifiable (Type A or D). Article 6 is closely aligned with ASTM E165 (general PT) and ASTM E1417 (aerospace PT) and references SE-165 and SE-1417 as adopted standards. Procedure qualification, material compatibility, dwell times, and lighting requirements form the core technical content.
Code compliance is only demonstrable if the evidence behind it is: the procedure revision in force, the inspector's certification state and the instrument's calibration status at the time of test. Atlantis NDT provides ASNT Level III consulting for procedure and written-practice work against this code, training toward the certifications that reference it, and inspection management software that keeps that evidence recoverable years later. Request a consultation.
How a standard like this is applied in an inspection programme
A standard is only half of the requirement. It defines how an examination is performed and, in some cases, how results are classified — but the acceptance criteria that decide whether a component stays in service normally come from the construction or in-service code governing the item, not from the examination standard itself. Confusing the two is one of the more common findings in a procedure review: a procedure that correctly cites the examination standard but applies acceptance criteria from the wrong code or the wrong edition.
What has to be in place for compliance to be demonstrable
A written procedure qualified against this standard for the specific materials, thickness ranges and geometries in scope — not a generic procedure covering everything
Personnel certified for the method and level under ASNT SNT-TC-1A, ANSI/ASNT CP-189, NAS 410 or ISO 9712, current on the date the examination was performed
Equipment, probes and reference standards in calibration on that date, with traceability to a national standard under ISO 17025
The applicable edition of the standard recorded against the examination, so historical work stays assessed under the edition then in force
Technique sheets under the same revision control as the procedure above them — the most frequently uncontrolled document in an otherwise compliant quality system
Edition changes
When a new edition is issued, new work moves to it from a defined effective date that you set and record; work already performed stays assessed under the edition in force at the time. Retrospectively applying a new edition to historical dispositions invalidates the original acceptance decision and creates a substantially larger problem than the one being solved.
Where this usually goes wrong
Not in the technical content, but in reconstruction. An auditor picks an issued report and asks which procedure revision applied, who performed the work and whether they were qualified on that date, and whether the instrument and reference blocks were in calibration. Programmes that hold only current state can answer none of those. Binding the document revision, the qualification state and the calibration state to each inspection record as it is created turns that from an investigation into a lookup.
Article 6 of ASME Section V sets out how a liquid penetrant examination is performed — procedure content, surface preparation, penetrant application and dwell, excess removal, developing and interpretation. It does not state what is acceptable. Acceptance criteria always come from the referencing construction code, which is the single most misread aspect of the article.
The standard technique is qualified for a surface temperature between roughly 40 and 125 degrees Fahrenheit (5 to 52 degrees Celsius). Working outside that window is permitted but only after qualification against a comparison block under the article's nonstandard temperature appendix, and a procedure that simply asserts a wider range without that qualification is a finding waiting to happen. Penetrant dwell is drawn from the article's dwell table by material and by the type of discontinuity sought, with ten minutes a common minimum, and developer dwell also carries a minimum before interpretation with a bounded window after it. Contaminant control matters for specific alloys: residual sulfur is restricted for nickel-base alloys and residual halogens for austenitic and duplex stainless steels and titanium, because those residues can cause cracking at temperature. Certification of the materials used is the evidence that closes that requirement, and it is routinely absent from otherwise complete data packages.
Source: ASME Boiler and Pressure Vessel Code Section V, Article 6, Liquid Penetrant Examination, including its mandatory appendices for contaminant control and nonstandard temperature qualification; ASTM E165/E165M; ASME Section VIII Division 1 Mandatory Appendix 8 as the referencing acceptance standard for vessel work.
What Article 6 controls, and where the corresponding requirement actually lives
Element of the examination
Set by Article 6
Set by the referencing code
Written procedure content and required variables
Yes
No
Surface preparation and cleaning method
Yes
Occasionally restricted further
Penetrant and developer dwell times
Yes
No
Standard temperature range, and qualification outside it
Yes
No
Contaminant limits for nickel alloys and stainless
Yes
May be tightened by specification
What size and type of indication is rejectable
No
Yes — always
Personnel qualification and certification
Referenced
Employer written practice to SNT-TC-1A or CP-189
A procedure that quotes acceptance criteria without naming the referencing code section has no basis for those criteria.
The acceptance criteria misunderstanding, and why it keeps happening
Section V is a methods document. Every article in it describes how to perform an examination, and none of them says what passes. Acceptance lives in the construction or inspection code that invoked the examination — Section VIII Division 1 for most pressure vessels, the applicable B31 book for piping, Section IX for procedure and performance qualification, API 510 or 570 in service.
The reason the error is so persistent is that Article 6 does contain evaluation language. It describes how to classify indications as linear or rounded and how to distinguish relevant from non-relevant. That is interpretation, not acceptance, and a procedure that carries those definitions and then states a rejection threshold without citing the code that set it has quietly invented an acceptance standard.
The practical test on a procedure review is simple: for every numerical acceptance limit in the document, ask which clause of which code it came from. If the answer is not immediately available, the procedure is not ready.
Temperature, dwell and the two most common technique errors
The standard technique assumes a surface temperature in the region of 40 to 125 degrees Fahrenheit. Below that, penetrant viscosity rises and it will not enter fine discontinuities in the stated dwell; above it, the penetrant dries in place and the developer cannot draw it back out. Both failures are silent — the examination looks like it was performed correctly and finds nothing.
Field work outside the window is legitimate and common, but it has to be qualified. The article provides for demonstration against a comparison block containing known discontinuities, run at the intended temperature and compared to the standard technique. That qualification record belongs with the procedure, and its absence is the most frequent nonconformance found on hot or cold weather penetrant work.
The second recurring error is developing time. Interpretation performed immediately after developer application misses fine indications that have not yet bled out, while interpretation left far too late allows bleed-out to spread until a fine linear indication reads as a broad rounded one. The article bounds the window at both ends for exactly this reason.
Contaminant control on stainless, duplex and nickel alloys
For austenitic and duplex stainless steels and for titanium, residual halogens left on the surface can contribute to stress corrosion cracking in service. For nickel-base alloys, residual sulfur can cause embrittlement at temperature. Article 6 therefore requires the penetrant materials used on those alloys to be certified against contaminant limits.
The evidence is a certification from the materials supplier covering the specific batch numbers used, retained with the examination record. Sites that buy consumables locally under time pressure frequently cannot produce it afterwards, and the examination is then not demonstrably compliant even though it was performed correctly in every other respect.
The control that works is procedural rather than technical: name the acceptable products in the written procedure and require batch certificates to be filed with the report at the time of the examination, not retrieved later.
Does ASME Section V Article 6 state penetrant acceptance criteria?
No. Article 6 governs how the examination is performed and how indications are interpreted, but acceptance is always set by the referencing code — Section VIII Division 1 for most pressure vessels, the applicable B31 piping book, or the in-service code such as API 510 or 570. A procedure quoting limits without citing that source has no basis for them.
What is the standard temperature range for liquid penetrant examination?
Approximately 40 to 125 degrees Fahrenheit, or 5 to 52 degrees Celsius, measured at the examination surface. Work outside that range is permitted only after qualification against a comparison block at the intended temperature, and that qualification record has to accompany the procedure.
How long must penetrant dwell on the surface?
The article's dwell table sets minimum penetration time by material and by the type of discontinuity being sought, with ten minutes a common minimum for weld and casting work. Developer dwell has its own minimum before interpretation and an upper bound after it, because indications continue to bleed out and eventually lose definition.
Why do stainless and nickel alloys need contaminant certification?
Residual halogens on austenitic and duplex stainless and on titanium can contribute to stress corrosion cracking in service, and residual sulfur on nickel-base alloys can cause embrittlement at temperature. Article 6 therefore requires certified penetrant materials for those alloys, evidenced by batch certificates retained with the examination record.
Which penetrant removal method should a procedure specify?
Whichever the surface condition and access support: water-washable for high volume on reasonably smooth surfaces, solvent-removable for local field work and touch-up, post-emulsifiable where maximum sensitivity on fine discontinuities is needed and rinse control is achievable. The method is a required variable, so changing it in the field means the procedure no longer covers the work.
Who is qualified to interpret an Article 6 examination?
Personnel certified under the employer's written practice, prepared to ASNT SNT-TC-1A or ANSI/ASNT CP-189, at the level the practice assigns to interpretation for that method. Section V references personnel qualification rather than defining it, so the written practice is the controlling document and a Level III approves the procedure itself.
Frequently asked
Can a penetrant examination be performed on a coated surface?
No. Coating bridges discontinuities and prevents penetrant entry, so the surface must be cleaned to bare metal over the examination area, and the cleaning method itself must not smear metal across the openings. Blasting and heavy wire brushing can close fine discontinuities and are restricted for that reason.
Is fluorescent penetrant always more sensitive than visible dye?
Generally yes, given adequate darkness and the required ultraviolet irradiance at the surface, because the eye detects a small fluorescent indication against a dark field more readily than a red indication against white developer. That advantage disappears entirely if ambient light control and lamp intensity are not verified.