Penetrant testing
(PT)
A welding crack, fatigue crack or other manufacturing defect can remain hidden from the naked eye — until it causes serious damage. Liquid penetrant testing (PT) reveals defects that extend to the surface
quickly, without radiation and on all non-porous materials, including austenitic stainless steel and aluminium.
- SFS-EN ISO 9712 certified
- From pre-processing to audit-ready inspection report
- Rapid reporting, even in under 24 hours
METHOD
PRINCIPLE
Dye penetrant inspection is based on capillary action: the penetrant, which has a low surface tension, is drawn into cracks and other discontinuities open to the surface of a clean and dry component being inspected. The penetrant is allowed to dwell for a sufficient penetration time
— usually 5–30 minutes depending on the type of defect and the material. Excess penetrant is removed in a controlled manner, after which a developer is applied to the surface.
The developer sucks up the remaining liquid from surface discontinuities of the penetration and makes the indications visible to the naked eye or under UV light. The fluorescent wet method achieves the highest sensitivity even for micrometer-scale cracking defects.
Note
PT is suitable for all non-porous materials regardless
about their magnetic properties.
It is the primary surface method for austenitic
for stainless steel and aluminium, for which MT is not suitable.
SUITABILITY
SUITABLE MATERIALS AND STRUCTURES
- Carbon steel and alloy steels
- Austenitic and ferritic stainless steel
- Aluminium and aluminium alloys
- Titanium, nickel and other non-ferromagnetic metal alloys
- Plastics and composites (non-porous)
- Ceramics and glass materials
- Castings, forgings and welded joints
FASTEST REPORTING IN THE INDUSTRY
Our AI-assisted reporting system enables a completed inspection report in even less than
in 24 hours — even for rush orders.
FLEXIBLE IMPLEMENTATION
Inspections are carried out at night and at weekends if necessary. On-site at short notice
— when the production schedule cannot be stretched.
Broadest material coverage
PT is the only surface testing method that is equally suitable for ferromagnetic and non-
for ferromagnetic materials — one method covers the entire production line.
AUDIT PROCESS STEP BY STEP
The surface to be inspected shall be cleaned of oil, grease, paint and loose matter in accordance with standard EN ISO 3452-2. Every surface-breaking discontinuity must be free from contamination prior to the application of the penetrant.
The penetrant is applied to the surface to be inspected by spraying, brushing, or dipping. The penetration time is usually 5–30 minutes. The method to be used—visible colour or fluorescent—is selected according to the object and requirements.
Excess penetrant is removed from the surface in a controlled manner either by water washing, solvent removal or after emulsification. Removal is always done in one direction, and the solvent must not be sprayed directly onto the surface.
The developer is applied evenly over the entire inspection area. The developer draws the remaining penetrant from the discontinuities to the surface, forming a visible indication. The development time is 10 to 30 minutes.
A Level II or III certified inspector assesses indications in visible light or UV light. Our AI-assisted reporting system delivers the completed inspection report in under 24 hours — ready to be attached to the QA/QC documentation.
TYPICAL APPLICATIONS
Welds in piping and prefabricated piping — in particular austenitic stainless steel and aluminium prior to installation
02
Pressure equipment welds and tank structures where non-ferromagnetic material prevents the use of MT (PED 2014/68/EU)
03
Structures in the shipyard and shipbuilding industries: aluminium hulls, titanium components and stainless steel
04
Components for the aircraft industry and other high-safety-class parts
05
Quality assurance of surface defects in castings and forgings prior to machining or commissioning
06
In-service inspections: identification of fatigue cracks and corrosion damage in equipment in service
ALONGSIDE PT AND MUIDEN NDT METHODS
The following comparison helps to select the most suitable method or combination of methods for the situation:
| Feature | PT | MT | DRT | UT / PAUT |
|---|---|---|---|---|
| Pintaviat | ✓ Excellent | ✓ Excellent | Limited | Limited |
| Subsurface defects (≤3 mm) | ✗ Not suitable | ✓ Good | Limited | ✓ Excellent |
| Internal volumetric defects | ✗ Not suitable | ✗ Not suitable | ✓ Excellent | ✓ Excellent |
| Non-ferromagnetic materials | ✓ Suitable | ✗ Not suitable | ✓ Suitable | ✓ Suitable |
| Freedom from radiation | ✓ Yes | ✓ Yes | ✗ It requires radiation protection | ✓ Yes |
| Pace on the pitch | ✓ Fast | ✓ Fast | ✓ Fast | Moderate |
| Material coverage | ✓ All non-porous | Only ferromagnetic | ✓ All metals | ✓ All metals |
| Hardware investment | ✓ Matala | ✓ Matala | High | Moderate |
Turku University Neuropsychological Rehabilitation Test
Magnetic particle testing
DRT — Digital X-ray
UT / PAUT — Ultrasonic Testing
Customer benefits
Widest material coverage
PT is suitable for all non-porous materials — metals, plastics, ceramics. It is particularly valuable for austenitic stainless steel and aluminium, for which MT is not suitable.
Speed and flexibility
A field-deployable method without heavy equipment or radiation-shielded areas.
Reporting in even less than 24 hours. Inspector on-site at short notice.
Safety and compliance
Detect surface-breaking cracks prior to commissioning. Reporting complies with
EN ISO 3452-1, SFS-EN ISO 9712 and project-specific requirements.
Cost-effectiveness
Low hardware cost and quick field deployment. Prevents
identifying faults through repair welding, warranty claims and production downtime
in the preparation phase.
HSE — safe to execute
CT does not contain ionising radiation and does not require protected areas or evacuation.
Suitable to be carried out alongside production without significant HSE arrangements.
Lifecycle management
Regular PT inspection identifies fatigue cracks and corrosion damage
at an early stage. Supports predictive maintenance throughout the lifecycle
Agent.
QUALIFICATION
STANDARDS AND CERTIFICATION
NDT Aura Oy's inspectors operate in accordance with the standards listed below — a technically competent and legally acceptable inspection result.
NDT programme
TOWARDS A COMPREHENSIVE NDT PROGRAMME
PT detects surface flaws in all non-porous materials, but comprehensive quality assurance often requires a combination of methods. NDT Aura Oy consults on creating the most suitable inspection programme based on the target's risk level and standard requirements:
FREQUENTLY ASKED QUESTIONS (FAQ)
Both detect surface defects, but the material coverage differs significantly. MT requires
ferromagnetic material — it is not suitable for austenitic stainless steel,
for aluminium, titanium or plastic. PT is suitable for all non-porous materials
regardless of magnetic properties. In ferromagnetic materials, magnetic particle testing (MT) provides
usually even higher sensitivity than PT also to subsurface defects.
No. PT is exclusively a surface method: it only detects flaws that reach or open to the surface. For detecting internal volumetric flaws, you need ultrasonic testing (UT/PAUT) or radiographic testing (dRT or RT). For comprehensive quality assurance, a combination of PT and dRT is recommended for critical structures.
Our AI-assisted reporting system enables a completed inspection report even
within 24 hours of carrying out the inspection. In urgent situations, we are often able to deliver
I will report either on the same day or the following morning.
Yes — PT is precisely the primary surface method for these materials. Unlike MT,
magnetic particle inspection does not require a ferromagnetic material, so it is suitable
excellently also for austenitic stainless steel, aluminium, titanium and
for other non-ferromagnetic materials.
PT is a radiation-free field-deployable method that requires neither a radiation-controlled area nor
evacuation of personnel. Inspections are carried out at night or at other quiet times if necessary
during production. An inspector can be arranged at 24 hours' notice.
A rough description of the object is sufficient: material, welding method or manufacturing method,
area or weld volume to be inspected, applicable standard or project requirement, and the desired
schedule. Drawings and isometric views speed up the preparation of the quotation.
Request for quotation
Request a quote for liquid penetrant testing
— fast response, audit-ready documentation
Tell us about the inspection object, material, applicable standard and schedule — we will respond to the request for quotation quickly. In urgent situations, call directly.
