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PAINTS & COATINGS

ANALYTICS FOR PAINTERS AND PAINT MANUFACTURERS

Complete solutions for release testing
from environmental simulation to damage analysis

We are your reliable partner for coating technology. With our extensive experience in the chemical and physical analysis of coatings, as well as our expertise in coating systems using plasma processes and vapor deposition techniques, we offer tailored solutions for your needs.

Our wide range of services includes:

  • Coating tests, which are especially required for approval processes in the automotive sector

  • Precise damage analysis for coating defects

 

Rely on our expertise and advanced methods to ensure the highest quality and precision in coating technology.

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PAINT TESTS

First article inspections according to automotive standards

Colour & Shine

Scratch test

Environment simulation
and weathering
Chemical resistance

Scratch resistance tests, or scratch tests for short, are carried out on plastics to test the quality of the adhesion of paints and coatings to plastics. To do this, a needle is moved over the surface with increasing pressure and it is tested how long the surface can withstand this load.

The cross-cut test evaluates the adhesion of paints to substrates and their resistance to damage. The painted surface is scratched in a cross shape and the adhesion is then checked using a peel test.

 

The quality of adhesion is assessed according to the standards DIN EN ISO 2409 (GT0 to GT5) or ASTM D 3359-02 (5B to 0B). These paint adhesion tests (cross-cut and grid cut tests) are carried out both before and after climatic storage.

The assessment of color and gloss is often done visually by comparing it to a reference sample or standard. Correct lighting is crucial to detect additional irregularities such as blistering or paint peeling.

 

Alternatively, color and gloss measuring devices enable the quantitative recording of color changes when changing batches or due to environmental influences. The measuring geometries used are standardized to ensure comparable results.

The cross-cut test evaluates the adhesion of paints to substrates and their resistance to damage. The painted surface is scratched in a cross shape and the adhesion is then checked using a peel test.

 

The quality of adhesion is assessed according to the standards DIN EN ISO 2409 (GT0 to GT5) or ASTM D 3359-02 (5B to 0B). These paint adhesion tests (cross-cut and grid cut tests) are carried out both before and after climatic storage.

During everyday use, paint comes into contact with a variety of chemicals. These are typically sweat, hand cream, sunscreen, various solvents, cleaning and disinfectants, and depending on the application, also cola or fuel.

 

Chemical resistance is usually tested by direct contact with the test medium. The test may be made more stringent by simultaneous friction or temperature stress. The changes in the paint are evaluated according to specific criteria.

Abrasion resistance, rub fastness or colour fastness

Mechanical contact with a painted surface can lead to a change in the surface (abrasion). The Crockmeter test is a test procedure for painted surfaces that is common in the automotive industry. This abrasion test is based on the DIN EN ISO 105-X12 standard. At the end of the test, the fabric is visually examined for possible discoloration and the painted surface for premature wear.

 

A crockmeter test is also suitable for simulating a combined effect of water or other media during mechanical resistance testing, thus significantly accelerating the aging of a surface.

Painted buttons or printed control elements, on the other hand, are preferably tested with an Abrex device. The actuation is simulated by a silicone finger with defined contact pressure and lateral displacement, whereby there is always a fresh friction fabric between the silicone finger and the surface to be tested. This fabric can also be exposed to a test medium.

Rockfall testing
Steam jet test
Salt spray testing

The resistance of vehicle paintwork to stone chips is of particular interest to the automotive industry. In a stone chip test, sharp-edged impact bodies of a defined size and shape are fired at the paint surface using compressed air to simulate stone chipping.

The type of impact body, the working pressure, the firing time and the angle of impact are specified in the relevant standards. The assessment of stone chip resistance is carried out by means of a visual comparison with images.

The steam jet test according to DIN EN ISO 16925 is used to assess the adhesive strength of paints and coatings. For the test, the paint is first scratched or milled into the substrate in the shape of a St. Andrew's cross. The edges of the St. Andrew's cross are then treated with a pressurized water jet under defined conditions. The defect pattern after the steam jet test is assessed by comparing it with image panels showing different levels of damage.

The salt spray test according to DIN EN ISO 9227 is used for painted metal parts. It simulates both the influence of salty air near the sea and the stress on a component caused by road salt.

A pH-neutral salt solution (NSS) is sprayed in a special chamber. This settles on the component and covers the surface with a corrosive salt water film. After the salt spray test, which lasts several days, the component is rinsed with distilled water to remove loose residues. It can then be checked whether the corrosion protection effect of a paint is fulfilled on all parts of a component or whether red rust is visible on the surface.

The salt spray test is well suited to compare the corrosion protection effect of different protective coatings.

DAMAGE ANALYSIS

Causes & sources of error

Blistering

Bubbles or blisters, which are pronounced as local elevations, are often caused by inclusions in the paint layer. These inclusions can, for example, come from contamination on an unpainted component or from foreign materials in the paint system.

Possible causes are unclean working conditions during painting or the inclusion of gases. For a precise analysis, the area usually has to be exposed by targeted preparation (cross-section).

Subsequently, analysis techniques such as scanning electron microscopy (SEM-EDX) or microspectroscopic methods (IR / Raman) are used to precisely analyze the composition in the area of the unevenness.

Paint craters

Paint craters represent a local depression in the paint and are often a result of wetting problems. The paint is pushed outwards in the defect area and thus reduced in the crater area. The effect can range from a slight reduction in layer thickness to paint-free areas on the component surface. If the cause of the paint crater is a particle in the crater center, similar analyses are used as for bubbles .

If no inclusions are visible, it is often still possible to analyze the paint crater. Release agents, grease or oils can often be detected on the paint surface using very surface-sensitive analysis methods. In addition, mechanical damage in the underlying paint layers (flaking) or in the unpainted component (dents or scratches) can also lead to paint craters.

Paint adhesion problems

Paint adhesion problems can be caused by contamination of the component surface, similar to wetting problems. Sometimes unsuitable paint systems are used which are not compatible with the material of the component.

Many plastics require surface activation such as flame treatment, fluorination or plasma treatment. If this is not carried out properly, paint adhesion can also be reduced. Special surface analysis or paint analysis is required for analysis in order to be able to detect the usually thin changes to the surface or the boundary layer.

Chalking

Chalking is a form of damage to paints caused by aging or external chemical influences. Pigment and filler particles are exposed in the area close to the surface due to the degradation of the paint's organic binding agent.

The increased light reflection on the rougher surface creates a brighter and more matte appearance. Chalking must be distinguished from the fading of pigment particles, which has very different causes.

Do you have questions?

Our experienced expert Rainer Ziel is on hand to offer you high-quality analytical solutions.

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