Tag Technical Standards

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.

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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.

– 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.

In non-destructive testing using Liquid Penetrant (LP) and fluorescent Magnetic Particle (MP) methods, the reliability of the inspection depends on a precise combination of factors: quality products, appropriate accessories, UV luminaires within technical specifications, and, most importantly, the correct visualization of the indications.

Within this context, one often underestimated aspect deserves special attention: the inspector’s eye protection. The use of glasses with an appropriate UV-A radiation filter is not only an occupational safety measure, but also a factor that directly impacts the quality of the interpretation of the results.

Fluorescence Assays and UV-A Radiation

Fluorescent END methods are based on the excitation of materials that emit visible light when exposed to type A ultraviolet (UV-A) radiation , generally with a wavelength around 365 nm .

However, continuous exposure to UV-A radiation requires strict control, both from the point of view of operator safety and the reliability of the inspection.

The Human Factor in Test Reliability

Even with:

• highly sensitive penetrating fluorescent lenses,
• fluorescent magnetic particles formulated according to technical standards,
• Even with UV lamps at the minimum required intensity, the test may be compromised if the inspector is not using adequate eye protection .

Vision is the primary tool for interpretation in fluorescent END. Any factor that causes:

• eye strain,
• glare,
• loss of contrast,
• visual discomfort,

It directly impacts the ability to identify, evaluate, and classify indications.

Function of UV-A Filtering Glasses in LP and PM Tests

Safety glasses with specific UV-A filters play a fundamental technical role during fluorescent inspections. Their function goes beyond basic protection.

Key technical benefits:

• Eye protection against prolonged exposure to UV-A radiation.
  Reduces risks associated with continuous exposure during inspection shifts.
• Improved contrast of fluorescent indicators:
  The filter reduces light reflected from the surface and enhances the visualization of the fluorescent glow emitted by the penetrant or particles.
• Reduced eye strain:
  Less eye effort results in more consistent and reliable inspections, especially in repetitive tasks.
• Increased accuracy in interpretation:
  A clearer and more comfortable field of vision contributes to safer technical decisions.

In industrial environments, where residual lighting and reflections can interfere with inspection, this visual benefit is even more relevant.

Integration with Quality Products and Accessories

Metal-Chek develops solutions for fluorescent testing by considering the entire process, and not just the isolated chemical product.

For LP and PM fluorescent methods to achieve their maximum performance, integration between the following is essential:

• Fluorescent penetrants and fluorescent magnetic particles developed in accordance with technical standards;
• UV lamps with appropriate wavelength and intensity compatible with regulatory requirements;
• Appropriate accessories , including safety glasses with UV-A filters compatible with the test’s operating range.

This systemic approach reduces misinterpretations, improves the repeatability of results, and reinforces a culture of quality in inspections.

Safety, Quality and Technical Responsibility

The use of UV-A protective eyewear should be understood as an integral part of good practices in fluorescent testing , aligned with safety guidelines and END reliability requirements.

Conclusion

Reliable fluorescent testing depends not only on high-performance products and equipment, but also on the human factor , particularly the quality of visualization and the inspector’s protection.

The use of glasses with adequate UV-A filter:

• protects vision,
• improves the contrast of the indications,
• reduces fatigue,
• and contributes directly to more accurate and reliable results.

In END, having good vision is just as important as applying the method correctly.

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

Continue deepening your knowledge: explore other technical articles on the Metal-Chek blog.

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In Magnetic Particle (MP) testing, the correct contrast between the surface and the magnetic particles is what guarantees the visibility of the indications and the accuracy of the results.
More than just a product, the Supermagna Contrast 104 Metal-Chek in Magnetic Particle Testing represents the practical application of the contrast concept in visible inspections, meeting the requirements of ASTM E709, NM 342 and PETROBRAS N-1598 standards.

Function of Supermagna Contrast 104 in Magnetic Particle Testing

The Supermagna Contrast 104 in Magnetic Particle Testing functions to create a uniform white background on the surface of the part or inspection area, upon which colored magnetic particles (visible method, usually black or red) accumulate, making indications of discontinuities more visible under ambient light. The uniform white background increases the visual difference between the part and the particles accumulated over possible surface discontinuities.

Without adequate contrast, subtle indications may go unnoticed, reducing the sensitivity of the assay and compromising the reliability of the results.

In summary, the Supermagna Contrast 104:

• It forms a highly reflective white background , ideal for visible testing;
• It increases the optical contrast between the surface and magnetic particles;
• It facilitates the visual interpretation of the instructions by the inspector;
• It directly contributes to the reproducibility and standardization of PM tests.

When to use Supermagna Contrast 104

Supermagna Contrast 104 is indicated for colored magnetic particle testing (visible method), conducted under visible illumination with a minimum intensity of 1076 lux, as established by ASTM E709, NM 342 and PETROBRAS N-1598 standards.

Precautions when applying and removing

In order to guarantee optimal performance and avoid interference with the result, it is recommended:

1. Surface preparation

The area to be inspected must be dry, clean, and free of oil, grease, paint, or mill scale. Prior cleaning with E59 Metal-Chek
is recommended, ensuring a perfectly prepared surface to receive Supermagna Contrast 104.

2. Uniform application

Supermagna Contrast 104 should be applied in a thin, even layer, avoiding excess.
Very thick layers compromise the sensitivity of the assay.

3. Drying

Allow to dry completely before applying the magnetic particles.
The surface should have a uniform, matte, and non-reflective appearance.

4. Removal

After testing, Supermagna Contrast 104 can be removed with a remover such as E59 or TMC 10 Metal-Chek, ensuring thorough cleaning without damaging the surface.

Why choose the Supermagna Contrast 104 Metal-Chek?

The Supermagna Contrast 104 Metal-Chek was developed for professionals seeking precision and performance in magnetic particle testing.

Main benefits:

• High coverage and quick drying , optimizing inspection time;
• An adherent and uniform layer , respecting the thickness limits;
• Intense optical contrast that highlights even the smallest details;
• Compatible with Supermagna BW 333, RW 222, SBW 333/O, SRW 222/O and YD 404 colored magnetic particles.

Technical notice

This content is for educational purposes only. The application of the test methods and parameters must follow a qualified procedure approved by a Level 3 Inspector.

Metal-Chek Excellence

The Supermagna Contrast 104 is more than just a support product:
it is an essential technical element to guarantee quality, sensitivity, and safety in visible magnetic particle testing.

Using the Supermagna Contrast 104 Metal-Chek means investing in standard, precision and reliability, fundamental pillars for those seeking excellence in Non-Destructive Testing.

“Precision is visibility — ensure reliable results with the Supermagna Contrast 104 Metal-Chek.”

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and follow us on  @metalchek

Discover the differences between the dry and wet methods of magnetic particle testing, their practical applications, and how to ensure reliable results according to technical standards.

The importance of the correct method in Non-Destructive Testing

Magnetic particle testing (MPT) is widely used in industry to detect surface and subsurface discontinuities in ferromagnetic materials.
The method is valued for its sensitivity, speed, and low operating cost, and is applied in sectors such as oil and gas, automotive, metallurgical, and aeronautical.

However, to ensure accurate results, it is essential to understand the differences between dry and wet methods, as each has specific characteristics and applications.

Principle of the test

The magnetic particle method is based on the magnetization of a ferromagnetic material. When the magnetic field encounters a discontinuity, a leakage field
is formed, attracting the magnetic particles and creating an indication  on the surface.

These particles can be colored (visible under white light) or fluorescent (visible under UV-A light), according to ASTM E709 – Standard Guide for Magnetic Particle Testing and NM 342 – Non-destructive testing — Magnetic particles — Discontinuity detection.

Magnetic particle testing – dry method: practicality and speed in the field

The dry method uses magnetic powder particles applied directly to the part during magnetization.
These particles adhere to the leakage field areas, forming indications visible to the inspector.

Main characteristics of the dry method

• Ideal for field testing or inspections of large structures;
• It eliminates the need for liquid vehicles, making the process portable and fast ;
• Suitable for rough, uneven or complex geometric surfaces ;
• It can be applied to parts at high temperatures (up to 180 °C).

Did you know?

• Metal-Chek’s SUPERMAGNA WD-55 particle can be used up to 400 °C .
• Metal-Chek’s SUPERMAGNA CRL 265 AG/SN particle can be applied in non-darkened environments with visible light intensity up to 1000 lx .

Limitations of the dry method

• Lower sensitivity than the wet method, especially in small discontinuities;
• It can lead to uneven particle buildup if not applied properly;
• The inspector needs experience to interpret the instructions.

Magnetic particle testing – wet method: precision and sensitivity

In wet spectroscopy, magnetic particles are suspended in water or oil, forming a homogeneous suspension applied to the surface during magnetization.
This technique offers greater particle mobility, resulting in improved sensitivity in detecting discontinuities.

Main characteristics of the wet method

• Suitable for high-precision testing ;
• It allows the use of fluorescent particles , inspected under UV-A light ;
• It requires strict control of the suspension regarding concentration and contamination;
• The measurements are verified using a pear-shaped decanter tube (ASTM E709).

For fluorescent particles, the ideal concentration is between 0.1 and 0.4 mL ; for colored
particles, between 1.2 and 2.4 mL, according to ASTM E709 and NM 342.

Limitations of the wet method

• Requires additional equipment (UV flashlight) for the fluorescent technique;
• A darkened environment is required for fluorescent techniques;
• Greater process control is needed (concentration and contamination).

Important notice:This article is for educational purposes only. The definition of the test method, technique, and parameters must be carried out by a Level 3 Inspector in a qualified and approved procedure.

Metal-Chek products in compliance with regulations

Metal-Chek offers complete solutions for magnetic particle testing, developed in accordance with the main international standards:

• Colored and fluorescent magnetic particles (dry and wet methods);
• Water-based suspension conditioners ;
• High-opacity contrast inks for inspections under white light;
• Supermagna HMM6 electromagnetic yokes , robust, portable and standard compliant.

All products are formulated to meet regulatory requirements, ensuring compliance, sensitivity, and repeatability of results.

When to apply each magnetic particle testing method

The dry and wet methods of magnetic particle testing are distinct, and their application should be based on the test conditions and procedural requirements.

Regardless of the method, using reliable products with proven quality is essential to ensure consistent and reproducible results — and that’s where Metal-Chek stands out.

Excellence in products for those seeking reliable results.

Metal-Chek provides complete END solutions: magnetic particles, contrast inks, conditioners, and electromagnetic yokes, developed according to the main ASTM, ASME, NM, and PETROBRAS standards, guaranteeing safety, precision, and technical compliance in every inspection.

Discover the complete Metal-Chek product line.

Contact  our team .

Follow @metalchek