Tag END Inspector

Every day, thousands of industrial structures, equipment, and components operate under severe conditions of pressure, temperature, and mechanical stress.

During manufacturing or throughout the lifespan of these materials, discontinuities can arise and, if not identified in time, can evolve into critical failures, directly impacting safety, operation, and industrial costs.

It is in this scenario that the Non-Destructive Testing (END) Inspector assumes an essential role.

Celebrated on March 27th, Non-Destructive Testing Inspector Day recognizes the importance of this professional who works on the front lines of failure prevention and industrial reliability.

What are Non-Destructive Tests (END)?

Non-Destructive Testing (END) methods are inspection methods used to evaluate materials, components, and structures without causing damage to the parts being analyzed.

These techniques allow for the identification of surface and subsurface discontinuities that can compromise structural integrity, directly contributing to the operational safety and reliability of industrial processes.

They are widely used in activities such as:

• Manufacturing of industrial components
• Weld inspection
• Preventive and predictive maintenance
• Quality control
• Structural integrity assessment

By enabling the early detection of discontinuities, END prevents unexpected failures, reduces operating costs, and increases the safety of operations.

The role of the END Inspector in industrial reliability

The END inspector is the professional responsible for performing, evaluating, and recording the results of inspections carried out using these methods.

Their role requires technical knowledge, mastery of applicable standards, and an understanding of inspection procedures.

Among their main responsibilities are:

• Evaluate the condition of materials and components
• Identify relevant discontinuities
• Interpret indications obtained during inspection
• Record results with technical accuracy
• Ensure compliance with standards and specifications

More than just performing tests, the inspector is responsible for ensuring the reliability of the results, a crucial factor for industrial safety.

Main Non-Destructive Testing methods used in industry

Several methods comprise Non-Destructive Testing. Among the most widely used are Liquid Penetrant Testing (LP) and Magnetic Particle Testing (MP).

Penetrant Testing (PT)

Liquid penetrant testing is used to identify surface discontinuities in non-porous materials.

The method consists of applying a highly penetrating liquid to the surface of the part. After an appropriate interval, the excess is removed and a developer is applied, allowing the indications to be visualized.

It is widely used in the inspection of:

• welding
• machined parts
• cast components
• metallic and non-metallic surfaces

Magnetic Particle Testing (MPT)

Magnetic particle testing is applied to ferromagnetic materials and allows the identification of surface or near-surface discontinuities.

During the test, the part is magnetized and particles are applied. In the presence of discontinuities, magnetic flux leakage occurs, forming visible indications.

It is used in the inspection of:

• welds
• shafts
• gears
• structural components
• parts subjected to mechanical stress

A fast, efficient method that is widely used in the industry.

Qualification and technical responsibility in END testing

Non-destructive testing (END) is not limited to the execution of the method; it also involves the correct interpretation of the observed indications.

Therefore, inspections must follow specific technical standards and procedures defined for each application.

The acceptance criteria, parameters, and procedures are established according to applicable standards and internal procedures of each company, under the responsibility of professionals qualified in the method.

The reliability of the results depends directly on three factors:

• Qualification of professionals
• Correct application of methods
• Proper use of materials and equipment

The role of Non-Destructive Testing in industrial maintenance

Non-destructive testing plays a strategic role in preventive and predictive maintenance, allowing the monitoring of component condition throughout their service life.

With this, it is possible to:

• Plan interventions in advance
• Avoid unexpected failures
• Reduce operating costs
• Increase equipment reliability

Applications of Non-Destructive Testing in major industrial sectors

Non-destructive testing is fundamental in various industrial sectors, especially where structural integrity is critical.

Among the main sectors are:

• Oil and gas industry
• Aeronautical sector
• Automotive industry
• Power generation
• Metal construction
• Industrial maintenance

In these environments, inspection directly contributes to ensuring the integrity of equipment, structures, and operational systems.

The importance of Non-Destructive Testing for industrial safety

Non-destructive testing is an essential part of modern industry, contributing to process reliability and operational safety.

By identifying discontinuities before they develop into critical failures, these methods ensure greater control over the integrity of equipment and structures.

On this Non-Destructive Testing Inspector Day, we reinforce the importance of the professionals who work on the front lines of inspection, ensuring that technical standards and quality criteria are met in every evaluation performed.

Excellence in products for those seeking reliable results

Metal-Chek provides complete solutions for Non-Destructive Testing: penetrant liquids, removers, developers, lighting fixtures and accessories, developed according to the main ASTM, ISO, ASME, NM and PETROBRAS standards, guaranteeing quality, safety and technical compliance in every inspection.

Speak with our  technical consultants  and find the ideal solution for your process.

Visit our  blog  and check out other technical content.

Discover our complete product line.

Follow Metal-Chek on Instagram, Facebook , and LinkedIn.

Aviation is one of the most stringent industrial sectors when it comes to operational safety. Aircraft are designed to operate under severe conditions of load, vibration, pressure variations, and continuous cycles of structural fatigue over thousands of flight hours.

To ensure that all components maintain their structural integrity over time, the aeronautical industry relies heavily on Non-Destructive Testing (END) .

More than just a verification step, ENDs (Non-Destructive Tests) are part of aviation safety culture. From the manufacturing of structures and components to maintenance programs throughout the aircraft’s lifespan, thousands of inspections are carried out to identify potential discontinuities before they evolve into critical failures.

Every safe flight depends on a series of technical inspections that ensure the structural reliability of the aircraft.

Non-Destructive Testing in the Aeronautical Industry

Non-destructive testing methods are used to evaluate the integrity of materials and components without compromising their future use.

In the aeronautical industry, different methods are applied as required by the aircraft manufacturer’s manual. Among the methods used are:
ultrasound
, radiography
, eddy currents
, liquid penetrant testing
, and magnetic particles.

Each method has a specific function within the inspection programs applied in the manufacturing and maintenance of aircraft.

Among these methods, fluorescent penetrant testing and fluorescent magnetic particle testing are widely used for the detection of discontinuities.

Technical rigor and materials control in aviation

The aeronautical sector adopts extremely rigorous criteria for the products used in inspection processes.

For example, the penetrating materials used in these processes must be qualified in the QPL — Qualified Products List.

Only listed materials may be used in certain aircraft inspection processes, ensuring standardization, traceability, and reliability in the results obtained.

Fluorescent penetrant liquid in aircraft inspection

Fluorescent liquid penetrant testing is widely used in the aeronautical industry to identify extremely fine surface discontinuities.

The method is based on the phenomenon of capillarity, allowing the penetrant to penetrate cracks or discontinuities open to the surface. After removing the excess and applying the developer, the retained penetrant returns to the surface, forming indications observed under ultraviolet illumination.

For aeronautical applications, the penetrants, removers, emulsifiers, and developers used must be properly qualified according to the applicable QPL list.

Metal-Chek offers the Sherwin Dubl-Chek line in Brazil, consisting of penetrant testing systems developed to meet the technical requirements of the aeronautical sector.

Fluorescent magnetic particles in ferromagnetic components

Magnetic particle testing is used to inspect components made from ferromagnetic materials.

The method involves magnetizing the component. When there is a surface discontinuity or a discontinuity near the surface, a distortion occurs in the magnetic field, forming a leakage field that attracts the magnetic particles applied to the part.

In the aeronautical industry, the test is typically performed using fluorescent magnetic particles in an oil-based liquid suspension, which provides greater sensitivity in the formation of indications.

In the context of the Metal-Chek line, fluorescent magnetic particles can be used in the aeronautical sector when applied in oil-based suspension, using the Supermagna OMC 10 MMS vehicle .

This combination allows for the proper formation of the suspension for application of the method, in accordance with the technical requirements adopted in aeronautical inspections.

Inspections throughout the aircraft’s lifespan

Non-destructive testing inspections are not limited to aircraft manufacturing.
These methods are part of ongoing maintenance and structural monitoring programs. Throughout the aircraft’s lifespan, components are periodically inspected to identify potential discontinuities caused by:
• structural fatigue
• repetitive load cycles
• vibration
• thermal variations
• severe operating conditions

This continuous monitoring allows for the identification of potentially critical conditions before they evolve into structural failures.

Air safety built into every inspection

Modern aviation safety is the result of a combination of advanced engineering, rigorous procedures, and reliable inspections.

Non-destructive testing is an essential part of this system, allowing the structural integrity of components to be evaluated without compromising their use.

Each inspection performed represents another level of assurance in the integrity of the aircraft, directly contributing to the safety of passengers, crews, and air operations worldwide.

Excellence in products for those seeking reliable results

Metal-Chek provides complete solutions for Non-Destructive Testing, with products developed according to the main ASTM, ISO, ASME, NM and PETROBRAS standards.

Among its solutions are systems for liquid penetrant testing, magnetic particles, and various consumables used in industrial inspections, contributing to consistent results, operational safety, and technical reliability.

Speak with our  technical consultants  and find the ideal solution for your process.

Visit our  blog  and check out other technical content.

Discover our complete product line.

Follow Metal-Chek on Instagram, Facebook , and LinkedIn.

In an industrial setting, Quality Control is responsible for ensuring that products and processes meet established technical, regulatory, and contractual requirements.

Non-Destructive Testing (END) is an integral part of this Quality Control system. It consists of technical tools used to verify the integrity of materials and components without compromising their future use.

However, in many industrial environments, there is a disconnect between operations and the Quality or END departments.

On one side, those who execute.
On the other, those who inspect.

When this relationship is misunderstood, the perception arises that inspection exists only to point out flaws or interrupt the process. This view generates internal noise and weakens the quality culture.

Operation and END are not competitors. They operate at different stages of the same objective: ensuring the technical conformity and reliability of the final product .

The role of the operation in process integrity

Execution is the foundation of any industrial result.

It is the operational team that applies procedures, controls parameters, performs welding, assembly, and adjustments that determine the component’s performance.

Quality begins in the production process. When execution is consistent and aligned with technical requirements, inspection tends to confirm this conformity.

The operation, therefore, is not merely an executor; it is an active part of the quality control system.

The role of END in technical verification

Non-destructive testing serves to verify whether a product meets integrity criteria.

END does not create discontinuities.
It evaluates what is already present in the material or what is inherent to the manufacturing process.

When a relevant indication is identified, the objective is technical: to prevent an unsuitable condition from progressing in the process or reaching the customer.

Internal inspection reduces major risks, avoids external impacts, and preserves the integrity of the production system.

When conflict arises

Disagreements between operation and quality often arise when inspection is perceived as an obstacle to the pace of production.

However, a nonconformity identified internally represents an opportunity for controlled correction. Conversely, a failure detected externally can compromise contracts, schedules, reputation, and operational safety.

END acts as a validation step within the production flow, not as a barrier, but as a mechanism for technical verification.

When operations and END work as partners

Mature industrial environments exhibit clear characteristics:

• The operational team understands the acceptance criteria applicable to the process;
• The inspector understands the variables and limitations of the production process;
• There is objective technical communication;
• Adjustments are treated as process improvements, not as personal conflicts.

When integration exists:

✔ Rework decreases
✔ Process predictability increases
✔ Approval rate improves
✔ Trust between departments is strengthened

Inspection is now recognized as part of the quality workflow, and not as an impediment.

Quality culture: shared responsibility

Quality is not exclusive to the END sector.

It involves planning, execution, verification, and continuous improvement. When everyone understands their role within the system, the environment becomes more collaborative and technically consistent.

A strong quality culture reduces costs and improves performance indicators in a sustainable way.

Procedures and products as elements of stability

The partnership between operations and END also depends on a solid technical foundation:

• clear and well-defined procedures;
• objective acceptance criteria;
• Standardization of inspection methods;
• Reliable and consistent inspection products.

When parameters are clearly defined and the products used deliver consistent, specification-compliant performance, the process becomes more stable and technically reliable. Consistency in results strengthens trust between departments.

Operation and Non-Destructive Testing operate at different stages of the process, but share the same purpose: to ensure that the delivered product conforms to integrity requirements.

Overcoming the idea that the quality sector is merely a “pointer of errors” is essential to consolidating more mature, cooperative, and efficient industrial environments.

When execution and verification work in an integrated way, the result is a more stable, safe, and reliable production system.

Excellence in products for those seeking reliable results.

Metal-Chek provides complete solutions for Non-Destructive Testing, with products developed according to the main ASTM, ISO, ASME, NM and PETROBRAS standards, contributing to consistent and technically reliable inspections.

– Read more technical content about END on our blog
– Follow Metal-Chek on Instagram: @metalchek and on LinkedIn

In Liquid Penetrant (LP) testing, each step directly influences the effectiveness of the test. After proper surface preparation and adherence to the correct penetration time, the removal of excess penetrant liquid plays a critical role in the inspection process.

Improper removal can mask relevant discontinuities, generate false indications, or hinder the correct interpretation of results. Therefore, this step must be performed with the same technical rigor as the other phases of the test, always in accordance with the qualified and approved technical procedure.

This article discusses the importance of removing excess penetrant fluid, the main errors associated with this step, and its direct impact on the reliability of the liquid penetrant test.

The role of excess removal in the LP assay

The principle of the Liquid Penetrant test is based on capillarity, which allows the penetrant to penetrate discontinuities open to the surface.

After the penetration time, the excess liquid present on the surface must be removed, leaving only the penetrant retained within the discontinuities. This condition is essential for the developer to act correctly, promoting the reverse capillary effect of the penetrant and the formation of visible or fluorescent indications.

Improper removal compromises this balance and directly affects the formation and clarity of the indications.

What characterizes proper removal of excess?

Proper removal of excess penetrant fluid must meet the following criteria:

• to remove the penetrant from the surface without removing it from inside the discontinuities;
• to preserve the sensitivity of the method;
• to enable reliable visual interpretation.

These criteria are not universal and depend on factors such as:

applicable technical procedure.

type of penetrant (visible or fluorescent);

specified removal method;

surface condition;

Methods for removing excess penetrant fluid

Methods for removing excess penetrant may vary depending on the type of penetrant and the application.

Among the most commonly used methods are:

• removal with solvent  (remover);
• removal with water (spray jet);

The choice of method should take into account its compatibility with the penetrant used.

Main mistakes in removing excess penetrant

Excess removal is one of the steps where the most frequent errors occur in the liquid penetrant testing method. Among the main errors are:

Excessive removal

Excessive application of solvent or mechanical action from an intense water jet can remove the penetrant retained in the discontinuities, resulting in:

• loss of relevant indicators;
• reduction in assay sensitivity;

Insufficient removal

Incomplete removal of excess residue leaves it on the surface, promoting:

• difficulty of interpretation;
• emergence of false or irrelevant indications.

Impact of improper removal on the interpretation of indications

The visual interpretation of the indications depends directly on the quality of the excess removal.

When this step is not performed correctly, the following may occur:

• blurred or fuzzy indications;
• difficulty in distinguishing relevant from irrelevant indications;
• Increased risk of improper rejections or undetected failures.

These effects directly impact the reliability of the inspection and technical decision-making.

Metal-Chek solutions for removing excess penetrant

Metal-Chek offers a complete line of removers developed specifically for Penetrant Testing, ensuring efficient and controlled removal of excess product.

These solutions are designed for:

• to preserve the penetrant retained in the discontinuities;
• Avoid blotchy or fluorescent backgrounds;
• ensure compatibility with different LP methods;
• to meet the requirements of the main applicable technical standards.

The choice of the appropriate remover should always take into account the technical procedure and inspection conditions.

Final considerations

Removing excess penetrant fluid is not a secondary step in the test—it is a determining factor in its effectiveness.

When performed correctly, according to a qualified and approved technical procedure, this step ensures:

• proper training of the indications;
• reliable visual interpretation;
• Reducing errors and rework;
• Greater safety during inspection.

In liquid penetrant testing, precision and control at each stage are fundamental to ensuring consistent and technically reliable results.

Excellence in products for those seeking reliable results

Metal-Chek provides complete solutions for Non-Destructive Testing: penetrant liquids, removers, developers and accessories, developed according to the main ASTM, ISO, ASME, NM and PETROBRAS standards, guaranteeing quality, safety and technical compliance in every inspection.

• Read more technical content on our blog.
• Follow Metal-Chek on Instagram: @metalchek
• Speak with the  Metal-Chek team  and learn about our solutions for non-destructive testing.

In Liquid Penetrant (LP) testing, the reliability of the result does not begin with the application of the penetrant, but rather with the preparation of the surface.

Even when appropriate products are used and all test steps are correctly performed, a poorly prepared surface compromises the sensitivity of the method, hinders the interpretation of the readings, and can lead to unreliable results. For this reason, surface preparation is considered one of the most critical steps in liquid penetrant testing.

This article addresses, in a technical and objective manner, the importance of surface preparation in Liquid Penetrant testing, its direct impacts on inspection, and the necessary precautions to ensure consistent results, always in accordance with the qualified and approved procedure.

The importance of surface preparation in liquid penetrant testing

The Liquid Penetrant test is based on the phenomenon of capillarity, which allows the penetrant to penetrate discontinuities open to the surface.

For this phenomenon to occur efficiently, it is essential that the surface is:
• clean;
• free of contaminants and dirt;
• in a suitable condition to allow direct contact of the penetrant with the discontinuities.

The presence of contaminants or surface residues increases surface tension, interfering with the action of the penetrant.

What characterizes a suitable surface for the test?

In general, the surface should:

• be free of oils, greases, moisture and chemical contaminants;
• not have loose scale, adherent oxidation or residues from previous processes;
• not have coatings or paints;
• not have spatter or welding residue;

These contaminants can prevent the penetrant from working properly and make it difficult to remove excess product.

Surface cleaning and preparation methods

Surface preparation methods must be defined according to the applicable technical procedure and vary depending on the material, the geometry of the part, and the stage of the industrial process.
Among the methods employed, the following stand out:
• solvent cleaning;
• chemical cleaning, applied in specific situations;
• ultrasonic cleaning
; • mechanical cleaning (brushing, sanding, grinding, tumbling);
• degreasing vapor.

The choice of method should consider not only the efficiency of the cleaning, but also the preservation of the surface integrity.

Care related to surface preparation

Even when cleaning is performed properly, surface preparation must consider factors that directly impact the reliability of the Penetrant Testing method.

Among the main precautions are:

• Ensure the surface is completely dry after pre-cleaning;
• Avoid solvent or cleaning product residue;
• Ensure the preparation method does not obstruct, deform the surface, or mask open surface discontinuities;

Metal-Chek solutions for surface preparation in LP

Metal-Chek provides complete solutions for surface cleaning and preparation in Liquid Penetrant Testing, including removers developed specifically for LP applications, compatible with different materials, test conditions and regulatory requirements.

These solutions contribute to:

• Efficient removal of contaminants;
• Compatibility with liquid penetrant testing methods;
• Operational safety;
• Greater reliability in inspection results.

Final considerations

Surface preparation is a determining factor for the success of the Penetrant Testing method. When performed correctly, according to a qualified and approved technical procedure, it ensures greater sensitivity of the method, reliable interpretation of the readings, and reduced rework.
More than a simple step, surface preparation should be treated as a fundamental part of the test, directly contributing to obtaining satisfactory results.

Excellence in products for those seeking reliable results

Metal-Chek provides complete solutions for Non-Destructive Testing: penetrant liquids, removers, developers and accessories, developed according to the main ASTM, ISO, ASME, NM and PETROBRAS standards, guaranteeing quality, safety and technical compliance in every inspection.

Read more technical content on our blog.
Follow Metal-Chek on Instagram: @metalchek.
Contact our technical consultants.

In Liquid Penetrant (LP) testing, the choice between visible penetrants (Type II) and fluorescent penetrants (Type I) is a technical decision that directly impacts the sensitivity of the inspection, the way indications are evaluated, and the reliability of the final result.

Although both types of penetrant are based on the same physical principle, their operational characteristics, inspection conditions, and sensitivity levels differ. This article presents an educational and technical approach, clarifying the main differences between visible and fluorescent liquid penetrants, their applications and limitations, always conditioned by the approved technical procedure.

What is liquid penetrant testing?

Liquid penetrant testing is a non-destructive testing method used to detect surface discontinuities open to the surface in metallic and non-metallic materials, provided the material is not porous.

The method is widely used in industrial inspection due to its versatility and ability to reveal fine discontinuities, provided it is performed in accordance with a specific technical procedure.

Common principle for visible and fluorescent penetrants

Both visible and fluorescent penetrants are based on the physical principle of capillarity, which allows the liquid to penetrate discontinuities open to the surface, even when these discontinuities are extremely small.

After the penetrant is applied and the excess surface product is removed, the product retained in the discontinuities is brought back to the surface by means of the developer, forming indications that will be evaluated during visual inspection.

The difference between the two types of penetrant testing lies not in the operating principle, but in how the indications are visualized during inspection.

Visible Penetrant Testing (Type II): general characteristics

Visible penetrant liquids utilize color contrast, typically red on a white background, to allow for visualization of the indications under adequate white illumination.

General characteristics:

• Inspection performed under visible light;
• indications observed with the naked eye;
• applicable in different industrial environments;
• Widely used in manufacturing inspections.

The reliability of the test depends directly on the intensity of the white light, the uniformity of the developer layer, and the correct execution of the test, respecting the procedure.

Fluorescent Penetrant Testing (Type I): general characteristics

Fluorescent penetrating liquids contain pigments that emit visible light when excited by ultraviolet (UV-A) radiation, allowing indications to be visualized in environments with controlled lighting.

General characteristics:

• Inspection performed under ultraviolet light;
• Indications observed by fluorescence;
• greater visual perception capacity in certain applications;
• Widely used in inspections that require a higher level of sensitivity and reliability.

In this method, the quality of the inspection is directly related to the UV-A lighting conditions, environmental control, and the correct visual adaptation of the inspector and the correct execution of the test, respecting the procedure.

Sensitivity and detection capability

Fluorescent penetrant testing (Type I) is more sensitive than visible penetrant testing (Type II). However, the most sensitive method is not always the most suitable for all applications.

The choice of penetrant type should consider factors such as the type of discontinuity to be detected, the manufacturing process, the surface condition, the industrial segment, the inspection environment, and the requirements established in the approved technical procedure.

Advantages of the Penetrant Testing Method

In general, the Liquid Penetrant test, in both the visible and fluorescent methods, offers the following advantages:

• a simple and widely used inspection method;
• relatively low operational cost when compared to other END methods;
• Ease of application, provided it is performed according to technical procedure;
• Direct visual interpretation of the instructions;
• good sensitivity for detecting surface discontinuities open to the surface , including fine and small-aperture discontinuities;
• Applicable to parts of different sizes and geometries, provided there is access to the surface to be inspected.

Limitations of the Penetrant Testing Method

Despite its advantages, the Liquid Penetrant test has technical limitations that must be considered:

• It detects exclusively open surface discontinuities and is not applicable to the detection of internal or subsurface faults;
• It is not recommended for porous materials ;
• It requires control of environmental conditions during the execution of the test, including temperature , which must be within the range specified in the technical procedure and applicable standards;
• Inadequate surface or environmental conditions can compromise the reliability of the indications.

Final considerations

The difference between visible and fluorescent penetrants goes beyond the appearance of the indication. It is a technical decision that involves physical principles, required sensitivity, inspection conditions, environment, type of discontinuity, and compliance with the approved technical procedure.

When correctly specified and applied, both methods offer reliable results and contribute to the integrity and safety of the inspected components.

Excellence in products for those seeking reliable results.
Metal-Chek provides complete solutions for Non-Destructive Testing: visible and fluorescent penetrant liquids, developers, removers, and accessories, developed according to the main ASTM, ISO, ASME, NM, and PETROBRAS standards, guaranteeing quality, safety, and technical compliance in every inspection.

Speak with the Metal-Chek team and learn about our solutions for non-destructive testing.

Access other technical articles.

– Follow Metal-Chek on Instagram: @metalchek

Liquid Penetrant Testing (LP) is one of the best-known and most widely used methods within Non-Destructive Testing (END) . Simple to perform, yet extremely meticulous in its details, it is fundamental for ensuring quality, safety, and reliability in critical components across various industrial sectors.

Despite its apparent simplicity, inconsistent results are almost always linked to flaws in the preparation, application, or control of test conditions —and not to the method itself. Therefore, understanding its principles is essential for anyone seeking reliable inspections.

What is Penetrant Testing?

The purpose of liquid penetrant testing is to detect discontinuities open to the surface of non-porous solid materials.

Among the most common discontinuities identified by the method are:

• Cracks
• Porosities
• Lack of fusion in welds

One of the great advantages of LP is its versatility. The method can be applied to both magnetic and non-magnetic materials, such as:

• Carbon steels and austenitic stainless steels
• Aluminum and magnesium
• Titanium

Furthermore, LP can also be used, under specific conditions, on ceramics, glass, and some plastics.

Physical Principle of the Liquid Penetration Test: Capillarity

The operation of the liquid penetrant test is based on the physical phenomenon of capillarity.

Capillary action allows a liquid to penetrate open discontinuities on the surface regardless of the orientation of the part, whether vertical, horizontal, or overhead, without depending on the action of gravity.

After applying the penetrant and removing the surface excess, applying the developer promotes the so-called reverse capillary effect, causing the liquid retained in the discontinuities to return to the surface, forming visible or fluorescent indications.

Steps of the Penetrant Testing Process

A reliable LP test follows six fundamental steps:

1. Surface preparation and cleaning
2. Penetrant application
3. Penetration time
4. Removal of excess penetrant.
5. Application of the developer
6. Inspection, recording and final cleaning

Each step must strictly follow the procedure qualified and approved by the Level 3 Inspector, respecting defined standards and parameters.

The Importance of Surface Preparation

The most critical step in liquid penetrant testing is undoubtedly the preparation and cleaning of the surface.

Complete removal of:

• Grease
• Oil
• Carepas
• Oxidation
• Paints and coatings

It is essential for the penetrant to act correctly through capillary action. Poorly prepared surfaces directly compromise the sensitivity of the test.

Types of Products Used in Penetrant Testing

The liquid penetrant test depends on the correct combination of three main groups of products:

1. Removers

Used for:

• Pre-cleaning of the surface
• Removal of excess penetrant, according to the method applied.

2. Penetrating

Classified according to the type of display:

• Fluorescent (Type I) – used under UV-A light.
• Visible (Type II) – observed under white light

And according to the removal method:

• Method A – water washable
• Method B – lipophilic post-emulsifiable
• Method D – hydrophilic post-emulsifiable
• Method C – solvent removable

3. Developers

Used to improve contrast and highlight indications, available in the following forms:

• Dry powder (Form a)
• Aqueous suspension (Form c)
• Aqueous solution (Form b)
• Non-aqueous suspension in solvent (Forms d | e)

Choosing the correct combination depends on the technical procedure, the type of material, and the discontinuity to be detected.

Common Questions about Liquid Penetrant Testing (LP)

Penetration Time: How Long to Let the Penetrating Agent Work?

For Metal-Chek products, the general recommendation is a minimum penetration time of 10 minutes.
In some specific applications, 5 minutes may be sufficient, provided that:

The procedure is qualified.

– Approval from Level 3 Inspector is required.

Can Penetrant Liquid Be Used on Stainless Steel?

Yes. The liquid penetrant (LP) test can be applied to austenitic stainless steel, duplex steel, and titanium, provided that the contaminant levels (Cl + F) indicated in the product’s certificate of analysis are observed.

Is Fluorescent Penetrant Always More Sensitive?

Yes. Fluorescent penetrant (Type I) exhibits greater sensitivity compared to visible penetrant (Type II).

However, greater sensitivity does not always mean better application. The choice of penetrant type should consider:

• Type of discontinuity
• Manufacturing process
• Surface condition
• Industrial segment
• Applicable procedure

Testing Conditions and Inspector Qualification

The penetrant testing process depends directly on the inspector’s visual ability and the lighting conditions.

Minimum lighting requirements:

• Visible Penetrant (Type II):
  • Visible light ≥ 1000 lux
• Fluorescent Penetrant (Type I):
  • UV-A light ≥ 1000 µW/cm²
  • Visible light < 20 lux

It is necessary for the inspector to periodically undergo visual acuity and color differentiation tests, such as:

• Visual acuity (Jaeger)
• Color differentiation (Ishihara)

Advantages and Limitations of the LP Test

Advantages:

• Simple and low-cost method
• Easy application and interpretation.
• High sensitivity to surface discontinuities
• Applicable to parts of any size and geometry.

Limitations:

• It only detects discontinuities open to the surface.
• Not applicable to porous materials.
• It requires strict temperature control.
  • Typical temperature range: 10 °C to 52 °C

Safety and Applicable Standards

The test should be carried out in well-ventilated environments, with the proper use of Personal Protective Equipment (PPE).

In fluorescent testing, the use of protective eyewear against UV-A light is mandatory.

Main standards applicable to liquid penetrant testing:

• ASME Section V – Article 6
• ASTM E1417
• ASTM E165
• ISO 3452
• NM 334
• PETROBRAS N-1596
• PETROBRAS N-2370

Conclusion

Liquid penetrant testing remains one of the most efficient tools for detecting surface discontinuities, provided it is performed with technical discipline, reliable products, and well-defined procedures.

Excellence in lead generation lies not in shortcuts, but in the rigorous control of each step of the process.

Excellence in products for those seeking reliable results.

Metal-Chek provides complete solutions for Non-Destructive Testing : penetrant liquids, removers and developers, developed according to the main ASTM, ISO, ASME, NM and PETROBRAS standards, guaranteeing quality, safety and technical compliance in every inspection.

Get in touch and follow the profile @metalchek for more technical content about END.

Industrial maintenance is undergoing a silent transformation—and one that is extremely relevant for those working in Non-Destructive Testing (END). UV lamps, essential for Liquid Penetrant (LP) and Magnetic Particle (MP) inspections, have evolved significantly in recent decades, driven mainly by the consolidation of UV LED technology. This change directly impacts the efficiency, quality, and reliability of inspections. More than that, it redefines the role of the inspector, who now has lighter, more durable, and more precise tools to perform critical analyses.

From vapor lamps to UV LEDs: the new era of lighting for END

For many years, mercury vapor-based UV lamps dominated the scene. Although functional, they had clear limitations: intense heating, fragility, high energy consumption, and unstable light.

With the arrival of UV LED lighting, the landscape changed.

Why does UV LED represent a technological leap?

• Stable and instant lighting , with no warm-up time.
• Much longer lifespan , reducing replacements and maintenance.
• Superior energy efficiency , with lower consumption and greater range in battery-powered versions.
• Increased mechanical strength , reducing field failures.
• The absence of toxic materials makes the equipment safer and more sustainable.

For those who inspect welds, critical parts, and structural components, this stability and precision are fundamental.

Portability: real productivity for those who work in the field

The inspector rarely works in comfortable spaces. Most inspections take place in hard-to-reach areas, elevated structures, confined spaces, or extensive pipelines.

The advancement of LEDs has allowed UV lamps to become:

• lighter ,​
• more compact ,
• more ergonomic ,
• more resistant ,
• and with greater operational autonomy .

Direct impacts on the inspector’s routine.

• Less fatigue during long shifts.
• Greater agility in accessing critical points.
• Less reliance on cables or external power sources.
• Greater precision in illuminating the inspected area.
• Reliability even in harsh environments.

Portability is no longer a “plus” but a strategic component of operational efficiency.

Durability and energy efficiency: savings that translate into performance

While traditional light bulbs frequently burned out, high-performance LEDs brought consistency and cost reduction.

Main benefits:

• Less maintenance and less downtime.
• Extended autonomy with long-lasting batteries.
• Reduced overall costs thanks to a longer lifespan.
• Stable UV intensity , ensuring adequate sensitivity in both low-level and mid-life modes.

For ongoing inspections and critical operations, this combination is indispensable.

Regulatory compliance: the importance of ASTM E3022

In END (Non-Destructive Testing), technology alone is not enough: it is necessary to meet the correct standards. ASTM E3022 is the international reference that establishes the minimum requirements for UV LED luminaires used in:

• Magnetic Particle (MP) Testing
• Penetrant Testing (PT)

The standard requires rigorous criteria, such as:

• minimum UV intensity suitable for the method;
• Uniformity of lighting in the inspection area;
• Visible radiation control;
• thermal stability;
• Mechanical strength suitable for industrial use.

Why is this fundamental?

Because lighting failures mean detection failures.
Without compliance with ASTM E3022, there are real risks:

• indications that do not appear;
• Unnecessary rework;
• inconsistent results;
• Problems in audits and certifications;
• security commitments.

The standard ensures that the inspector works with adequate lighting to detect even the most subtle indications.

The practical impact of these advances on the quality of inspections

The evolution of UV LED lighting directly influences:

• The accuracy of discontinuity detection;
• the pace at which inspections are carried out;
• The ergonomics of fieldwork;
• The safety and traceability of the process;
• The reliability of the results delivered.

In sectors such as oil and gas, automotive, aerospace, and metalworking, this translates to lower operational risk and greater control over asset integrity.

UV LED lighting as a protagonist in the new era of END

The combination of portability, energy efficiency, durability, and regulatory compliance has transformed UV LED luminaires into essential tools for modern inspections.

Technology not only makes the inspector’s job easier — it raises the quality of the entire industrial maintenance chain.

Stay tuned for updates!

We will soon be presenting important news related to our line of lighting fixtures for END (Non-Destructive Testing).
Follow the blog and our social media to stay updated on the launch.
Technical lighting, precision, and innovation for those who demand reliable results.

In industrial settings, consumables for Non-Destructive Testing (END) are true allies of reliability. Penetrant liquids, magnetic particles, and developers are formulated to deliver sensitivity , contrast, and stability —three pillars that support the precision of inspections.

One critical point that cannot be overlooked: storage. When done improperly, it accelerates product degradation and directly compromises the test results.

And in industrial inspection, a mistake never comes alone — it translates into rework, costs, and risks.

Therefore, taking care of expiration dates and storage conditions is not just a good practice:  it is fundamental to maintaining the performance and technical compliance required in industrial inspections.

Why proper storage is essential

END consumables undergo rigorous formulations, developed to maintain their properties throughout use. However, factors such as humidity, temperature, and expiration date can compromise them.

• sensitivity in detecting discontinuities,
• contrast of the indications,
• chemical stability
• Repeatability of results .

When exposed to unsuitable conditions, they may:

• to crowd together,
• evaporate,
• change color, odor or viscosity,
• lose sensitivity,
• to generate false indications or mask real flaws.

A degraded product can alter the test results.

Effects of moisture on END consumables

Moisture is one of the main factors that affect the quality of consumables.
When present in excess, it can cause clumping of powdered consumables, changes in product characteristics,  affecting performance and sensitivity.

To avoid these effects, it is important to store the products in dry, well-ventilated places, protected from condensation and sudden temperature changes. In addition, it is recommended to keep the packaging tightly closed, especially in environments with high relative humidity.

Temperature and chemical stability

Temperature has a direct impact on the chemical stability of END consumables. Excessive heat
can alter pigments, cause the evaporation of volatile components, and compromise the performance of penetrants, developers, and magnetic suspensions.
Extreme cold, on the other hand, can cause the crystallization of components , rendering the product unusable.

To ensure optimal stability and sensitivity, it is recommended to store consumables as follows:

• In cool environments , with controlled temperatures between 5°C and 40°C;
• Keep away from heat sources, direct sunlight, and open flames;
• Avoid prolonged exposure to temperature variations.

Validity and usage control

Each consumable has an expiration date defined by the manufacturer, which must be strictly respected.
After this period, there is no guarantee of stability or performance — the product may show changes in color, odor, viscosity, or the formation of residues, indicating degradation of the active components.

In addition to the expiration date, it’s important to check:

• Storage conditions ;
• Label integrity and batch identification .

Good practice includes using the FIFO (first in, first out) principle, ensuring that older products are consumed before new ones.

Good storage practices

1. Store upright to prevent leaks or deformation of the packaging.
2. Avoid stacking cans or aerosols to prevent pressure damage.
3. Keep the products sealed until the moment of use.
4. Do not mix products from different manufacturers — chemical compatibility is not guaranteed.
5. Visually inspect the product before use: changes in appearance indicate loss of stability.
6. Use appropriate storage methods , keeping them away from electrical sources and intense heat.

These measures help preserve the original characteristics of END consumables and ensure testing with maximum repeatability and reliability.

Why follow these guidelines?

Following good storage and expiration date control practices reduces costs, avoids rework, and ensures the integrity of inspection results .
Proper preservation of END consumables is an essential part of quality management in industrial inspections , ensuring that each application maintains the expected performance standard from the first to the last use.

Properly storing and controlling END consumables is an investment in reliability, safety, and durability .
By maintaining ideal temperature, humidity, and shelf-life conditions, inspection ensures consistent results that comply with industry technical requirements.

The inspection begins long before the test is performed — it begins in the warehouse.

Metal-Chek provides complete solutions for Non-Destructive Testing: penetrant liquids, magnetic particles, developers and accessories, developed with cutting-edge technology to offer safety, precision and reliable results in every inspection.

○ Need technical support? Our Metal-Chek consultants are ready to help.

○ Keep learning: explore more technical articles about END on our blog .

○ Join the community of END inspectors and professionals — follow @metalchek .

In Liquid Penetrant Testing (LP), the developer plays an essential role: it is what makes the indications of discontinuities visible. Its function is to form a thin, uniform layer on the clean, dry surface, acting by reverse capillary action —promoting the return of the penetrant retained in the discontinuities to the surface, where the visible indication is formed for evaluation under white/visible light (for visible penetrants) or ultraviolet UV-A light (for fluorescent penetrants), allowing for a clear and reliable assessment.

More than just a product, the developer is a crucial factor in the sensitivity and reliability of the test. Therefore, understanding its variations and applications is fundamental for efficient inspection that complies with technical standards.

Types of Developer and Their Differences

Developers are classified according to their form, and the correct choice depends on the type of penetrant and the inspection environment.

The main categories are listed below:

1. Dry Developer

Dry developer consists of fine powder and forms a light, absorbent film. It is applied to the dry surface after the penetrant has been removed.

• Application: by immersion, dust chamber, electrostatic spray or spraying.
• Advantages: high sensitivity and solvent-free; ideal for fluorescent penetrants.
• Metal-Chek product: D72 Powder Developer , ready to use, non-flammable and easy to remove.

2. Aqueous Developer

Developer prepared in aqueous solution, which forms a uniform white film after drying.

• Application: by immersion or spraying.
• Advantages: homogeneous coverage, easy dispersion, and concentration control.
• Metal-Chek product: D76 Water-Soluble Developer , diluted from 15 to 60 g/L of water, indicated for use with fluorescent penetrants.

3. Non-Aqueous Developer

It consists of fine white particles suspended in solvent, forming an opaque, high-contrast white background. It is the most common type in the field, especially in visible penetrant inspections.

• Application: Apply in a thin, uniform layer by spraying (aerosol or compressed air gun).
• Advantages: quick drying, excellent contrast, and easy removal.
• Metal-Chek product: D70 Non-Aqueous Developer , available in bulk (5L) and D70 (HI) hydrocarbon propellant aerosol versions, both suitable for fluorescent and visible penetrants.
• Operating temperature: 10 to 52 °C.

Good Application Practices (for all types)

• Apply the developer in a thin, even layer , avoiding excess that could mask indications.
• Allow to dry  before inspection.
• Use products within their expiration date and store them according to temperature and ventilation recommendations.
• Inspect under adequate lighting — white light ≥ 1076 lux for visible penetrants or UV-A ≥ 1000 µW/cm² and ambient light ≤ 21 lux for fluorescent penetrants.

Technical Notice

This content is for educational purposes only.The selection of the developer type, application parameters, and operational precautions must follow a qualified procedure approved by a Level 3 Inspector.

Choosing the right developer directly impacts the sensitivity and reliability of penetrant testing.
Each type— dry , aqueous , or non-aqueous —has specific characteristics that must be selected according to the type of penetrant, the inspection conditions, and the required level of sensitivity. The correct choice enhances the quality of the END and ensures more accurate technical decisions.

Revealing the invisible requires precision — choose Metal-Chek products.
The solution for non-destructive testing.

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