Tag Weld inspection

When ultrasound is mentioned, the immediate association is usually with the medical field.
In industry, however, ultrasound testing (UT) is one of the most strategic methods for controlling structural integrity.

In critical welds, pressure vessels, piping, aeronautical components, and thickness measurements, relevant operational decisions are made based on the ultrasonic response.

And there is a variable that is often underestimated in this process:
the quality of the coupling.

Physics is non-negotiable: acoustic impedance and transmission

Industrial ultrasound relies on the efficient transmission of sonic energy from the transducer to the material.

Air, due to its extremely low acoustic impedance compared to metals and composites, acts as an almost total barrier to sound transmission. The couplant exists to reduce this impedance difference between the media and allow acoustic propagation.

Without proper coupling, there is no reliability. Therefore, the coupling agent must be treated as an integral part of the system, not as a secondary item.

A/US 2000 – Rheological control and operational adaptability

OA/US 2000 is a powdered couplant that allows for controlled dilution. This feature offers an important technical advantage: viscosity adjustment according to the application.

This is relevant when:

• There are variations in position (horizontal, vertical);
• The surface has irregularities;
• The rehearsal is prolonged;
• The procedure requires specific controls.

The possibility of adjustment allows adapting the behavior of the couplant to the dynamics of the inspection.

Furthermore:

• It is removable with water;
• It operates between 5 °C and 60 °C;
• It meets the main industrial specifications applicable to the method.

For operations that value control and flexibility, this profile offers an operational advantage.

A/US 3000 – Standardization and immediate stability

OA/US 3000 is supplied in ready-to-use gel form.
Its main feature is the reduction of operational variables.

On the field, this means:

• direct application;
• stabilized viscosity;
• less need for preparation;
• Greater standardization among teams.

Its low volatility allows for extended inspections, while good adhesion contributes to layer uniformity and signal stability.

For routine inspections, thickness measurements, and field applications, standardization reduces the risk of operational variation.

It’s not about “which is better,” it’s about process variables

The choice between the A/US 2000 and A/US 3000 should not be based on personal preference.

She should consider:

• nature of the inspection;
• surface condition;
• work environment;
• application time;
• requirements of the qualified technical procedure.

Both fulfill the essential function of eliminating the air interface and allowing efficient transmission of ultrasonic energy.

The difference lies in the operational behavior and how each one integrates into the process.

Industrial strategy: reduce variables, increase reliability

Mature companies understand that reliability doesn’t depend solely on state-of-the-art equipment.

It depends on the sum of:

• parameters correctly defined;
• Proper calibration;
• Control of operational variables;
• Standardization of inputs.

The couplant is one of those variables.

When the interface is stable, the signal is stable.
When the signal is stable, the interpretation is more reliable.
And when the interpretation is reliable, the technical decision gains consistency.

In industrial ultrasound, the quality of information begins at the interface between the transducer and the material

The coupling agent is not a detail.
It’s part of the system.

Whether in powder form (A/US 2000) or ready-to-use gel (A/US 3000), the choice should be aligned with the established technical procedure and the actual inspection conditions.

Industrial ultrasound goes far beyond the hospital setting.
It protects assets, preserves structural integrity, and supports critical technical decisions.

And it all starts with the interface.

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, guaranteeing quality, safety and technical compliance in every inspection.

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

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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

Non-Destructive Testing (END) plays a fundamental role in industry. Far beyond a technical inspection step, END is a strategic tool that directly contributes to product quality , operational safety , cost reduction , and the preservation of life .

In an increasingly demanding industrial environment, where failures can result in accidents, unscheduled downtime, and significant financial losses, END (Non-Destructive Testing) acts preventively, allowing the identification of discontinuities before they evolve into critical failures. This control impacts the entire organization, from the purchasing department to senior management, strengthening the industry as a whole.

Non-Destructive Testing: More than inspection, an industrial strategy

Non-destructive testing comprises a set of inspection methods used to assess the integrity of materials, components, and structures without compromising their future use.

Methods such as Liquid Penetrant Testing (LP) , Magnetic Particle Testing (MP) , and Leak Detection are widely applied in manufacturing, maintenance, and operational inspections. They allow for the early identification of discontinuities, defects, or inadequate conditions, ensuring greater reliability in industrial processes. When correctly specified and executed, END ceases to be merely a regulatory requirement and becomes an instrument for quality and risk management .

Strengthening industry and preserving life

One of the main pillars of Non-Destructive Testing is safety. The integrity of equipment, structures, and components is directly related to the protection of people, the environment, and industrial assets.

Undetected defects can result in serious accidents, leaks, structural collapses, and operational interruptions. END (Non-Destructive Testing) acts preventively, significantly reducing these risks by identifying discontinuities in their early stages.

By investing in reliable inspections and appropriate END products, industry strengthens its operations, increases the reliability of its assets, and plays an essential role in preserving life .

Cost reduction and impact on the company’s financial health

Although often viewed merely as an operational cost, Non-Destructive Testing, in practice, represents an investment with a measurable return.

Early fault detection prevents:

• unscheduled stops;
• rework and scrapping;
• catastrophic failures;
• Accidents with human, environmental, and financial impact.

When compared to the cost of an operational failure, the investment in END (Non-Destructive Testing) and quality products becomes small. Companies that adopt routine inspections and structured END programs show greater cost predictability and better financial health over time.

END as a quality inspection and routine tool

Non-destructive testing is widely used as a quality control tool, both in production processes and in maintenance programs.

They act at different times:

• Raw material inspection;
• welding process control;
• verification of manufactured components;
• periodic maintenance inspections.

Routine END inspection demonstrates industrial maturity, enabling traceability, standardization, and compliance with technical standards and contractual requirements. In this way, END directly contributes to the final quality of the product delivered to the customer.

How a quality product in END impacts the entire company

Choosing the right products for Non-Destructive Testing goes far beyond the technical aspects. A low-quality END product can generate hidden costs and compromise the entire inspection system.

The impact is reflected in various sectors of the company:

Purchases and acquisitions

Reliable products reduce rework, internal complaints, and performance variations, facilitating standardization and supplier management.

Maintenance

Consistent results allow for more accurate diagnoses, avoiding unnecessary interventions or recurring errors.

Quality

Reliable testing reduces nonconformities, unwarranted rejections, and increases the credibility of inspection results.

Facilities and operation

The reliability of END (Non-Destructive Testing) ensures operational continuity, safety, and a longer lifespan for assets.

Board of Directors and Management

Risk reduction, cost predictability, and preserving the company’s image directly impact strategic decisions.

Financial health: Fewer failures, fewer accidents, and fewer stoppages result in greater operational efficiency and business sustainability.

Non-Destructive Testing Solutions as a Reliability Factor

For END (Non-Destructive Testing) to fulfill its strategic role, the correct combination of the following is fundamental:

• appropriate test method;
• qualified and approved technical procedure;
• qualified professionals;
• Products developed in accordance with applicable technical standards.

Reliable END solutions contribute to consistent results, operational safety, and regulatory compliance, strengthening the entire industrial chain.

Final considerations

Non-destructive testing is an invisible pillar of modern industry. It protects people, ensures the integrity of assets, reduces costs, and sustains the quality of products and processes.

Companies that view END (Non-Destructive Testing) merely as an obligation miss the opportunity to use it as a strategic tool for management, safety, and sustainability . Conversely, those that invest in reliable inspections, quality products, and technical expertise strengthen their operations and build a legacy of industrial excellence.

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 the quality, safety and reliability of industrial inspections.

👉 Access our blog and check out various technical content about END
👉 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.

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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.

In Fluorescent Penetrant (LP) and Fluorescent Magnetic Particle (FM) tests, UV-A light is not just an accessory—it is a critical detection tool. The quality of illumination used by the inspector defines what is seen… and what can go unnoticed.

To ensure that the UV-A source truly offers stability, safety, and adequate performance, the industry has adopted ASTM E3022-25, now considered the most rigorous technical standard in the world for UV-A LED luminaires used in END (Non-Destructive Testing).

Why was ASTM E3022-25 created?

ASTM E3022-25 was created precisely to establish minimum and verifiable requirements that define when a UV-A LED light fixture is truly suitable for industrial inspections, especially in critical applications such as:

• Aerospace
• Automotive
• Oil & Gas
• Industrial maintenance
• Welding and structural integrity

In this way, the standard ensures that the luminaire operates within the necessary parameters, guaranteeing that the fluorescence of the penetrants and particles is visible and reliable.

What does ASTM E3022-25 require in practice?

The standard dictates that the luminaire must be tested as a complete unit, not by individual components. This eliminates the possibility of partial tests that do not represent actual performance.

Main requirements that a UV-A luminaire must meet:

* If applicable

This eliminates variations between units and ensures repeatability in the field.

Why is this standard important for safety and for the outcome of the inspection?

A non-compliant light fixture can:

• Reduce the useful inspection area;
• Change the intensity without the operator noticing;
• To utilize a wavelength and have a broad spectrum and reduce fluorescence;
• Increase the risk of undetected failures;
• Generating non-conformities in technical audits (NADCAP, etc.).

For industries that work with critical components — such as structural welds, shafts, bearings, rotors, aeronautical components, and automotive parts — this difference is crucial.

Relationship of ASTM E3022-25 with other END standards

The standard is cited and used as a reference in several technical documents, such as:

• ASTM E1417, ASTM E165 (Liquid Penetrant)
• ASTM E1444, ASTM E709, ASTM E3024 (Magnetic Particles)
• ISO 3059 (Lighting requirements for END)

This reinforces the importance of E3022-25 as a quality base for any UV-A lamp used professionally in END (Non-Destructive Testing).

Final message for inspectors, engineers, and quality managers.

ASTM E3022-25 is not merely a regulatory formality.

It represents a commitment to:

Reliability of the indications

• Operational safety
• Standardization of inspection
• Reproducibility of results
• Compliance with audits

Thus, by using UV-A lamps certified according to this standard, the professional reduces risks, in addition to increasing precision and strengthening the entire quality chain of Non-Destructive Testing.

Stay tuned for updates!

We will soon be presenting important news related to our line of lighting fixtures for END (Non-Destructive Testing).
Follow our blog and social media channels to stay updated on upcoming releases.
Contact our technical consultants .

Excellence in products for those seeking reliable results.

Metal-Chek offers complete solutions for Non-Destructive Testing, developed according to the main technical standards of the sector.
Count on our line of consumables, accessories, and equipment designed to guarantee safety, precision, and compliance in every inspection.

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.

The reliability of results in Non-Destructive Testing (END) depends directly on the chemical compatibility between the products used. Mixing penetrant liquids, removers, and developers from different manufacturers can compromise sensitivity, generate reading errors, and even invalidate the test.

To ensure consistent performance, traceability, and chemical stability at all stages, it is essential to use complete systems from a single manufacturer—such as the Metal-Chek line—always strictly following the manufacturer’s technical guidelines and applicable procedures.

The Importance of Chemical Compatibility in Non-Destructive Testing

In Non-Destructive Testing (END) , product compatibility is one of the most critical factors in ensuring accurate results.
In methods such as Liquid Penetrant Testing (LP) , each step— pre-cleaning, penetration, removal, and development —depends on a specific and controlled chemical formulation.

Mixing products from different manufacturers, even within the same category, can directly impact the sensitivity of the assay.

All materials used in an assay must be chemically compatible and, preferably, from the same manufacturer.
This standardization ensures the traceability, repeatability, and reliability of the results, as well as guaranteeing that the assembly was developed and tested to operate in chemical equilibrium under controlled conditions.

Risks of Mixing Different Products in Non-Destructive Testing

The use of penetrating fluids, removers, and developers of different brands or chemical compositions compromises the integrity of the process.
Among the main risks are:

• Loss of contrast between the background and the indications;
• Improper removal of the penetrant during cleaning;
• Unexpected chemical reactions between solvents, pigments, and additives;
• Forming false indications in reading;

These factors can lead to false results, rework, and delays, as well as jeopardize the reliability of the inspection and operational safety.

Metal-Chek Line for Liquid Penetrant Testing (LP)

The Metal-Chek line was developed to ensure complete chemical compatibility between all stages of the assay — pre-cleaning, penetration, removal, and development — guaranteeing stable performance, adequate sensitivity, and reproducible results in any industrial application.

Technical Compliance

Metal-Chek products are developed in accordance with applicable national and international standards and must be used in a compatible system by properly trained and qualified personnel.
The combined use of Metal-Chek products ensures uniformity of performance, traceability, and technical compliance, eliminating the risk of incompatibility between stages and guaranteeing accurate and reliable results.

Chemical compatibility is the key factor in ensuring the reliability of liquid penetrant testing.

Mixing products from different manufacturers compromises the chemical balance of the process and can lead to incorrect results, rework, and even inspection failures.

To ensure sensitivity, traceability, and performance in accordance with international standards, it is essential to use all products from the same system and manufacturer, strictly following the manufacturer’s guidelines and applicable procedures.

Compatibility equals reliability — use the complete Metal-Chek system and ensure accurate results.

Continue Learning with Metal-Chek

Explore other technical articles on our blog .Discover our complete line of LP and PM products, developed according to ASTM, ISO, ASME, NM and PETROBRAS standards.Talk to our technical consultants and find the ideal solution for your inspection process.Follow our Instagram page: @metalchek