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Surface protections - Painted products
»Specifications
Chemical analysis, adhesion, hardness, thickness, gloss
»Resistance tests
Resistance to corrosion, light, impact, stress and liquids
»Colour tests
Colour determination, colour change
Chemical analysis
As for the chemical analysis of the protective surface layers, several analytic techniques can be applied depending on the kind of coating: FT-IR spectrometer, ICP spectrometer, energy dispersion sound microanalysis, etc.
Adhesion – Squaring test (UNI EN ISO 2409:1996)
Empiric test procedure to evaluate the strength of painted product films to stripping from the support. The coating adhesion is evaluated by engraving a squared grid on the film and then checking its stripping strength by applying adhesive tape.
Hardness determination – Pencil method (UNI 10782:1999)
To assess the hardness using this method, the painted surface has to be scratched by a pencil of set hardness.
Thickness determination
The thickness can be in a non-destructive way by ultrasounds or a magnetic feeler gauge, or in a destructive way by sectioning, observing and measuring the sample through an optic microscope.
Gloss determination (UNI EN ISO 2813:2001)
Determination of the specular gloss of non-metalized paint films. The test is carried out by a glossmeter.
Resistance to neutral salt spray (Uni ISO 9227)
Corrosion resistance tests in neutral salt spray (NSS), acetic acid salt spray (AASS) and copper acetic salt spray (CASS) according to standards ASTM B117 and ISO 9227 on metals and alloys, metallic coatings (anodic and cathode), conversion coatings, anodizing coatings and organic coatings of metallic materials.
Determination of resistance to humidity (UNI EN ISO 6270-1)
Method for evaluating the resistance of paints, varnishes and similar products in high humidity conditions, according to the coating requirements or the product specifications. It indicates the performance likely to be obtained in severe exposure conditions, with a continuous surface condensation. This procedure can highlight coating damages (blistering, spots, softening, wrinkling and brittleness) as well as support deterioration.
Lightfastness accelerated test by exposure to the radiation of a xenon lamp (UNI 9397-89)
Sun ray resistance test (lithtfastness) of metallic materials and relevant coatings carried out according to 3 radiation levels by means of a 1500-W Xenon lamp; automatic alternated setting of radiation cycles and moisturizing cycles; filtering of the lamp spectrum emission depending on the sample exposure during use / (sun light at high altitude, at sea level, passing through a window glass).
Cylindrical mandrel bending (UNI EN ISO 1519-98)
Empiric test method to assess the resistance of a paint or varnish film to cracks and/or to the stripping from a metallic support, when this is bent on a cylindrical mandrel under standard conditions.
Determination of the resistance to fluids (UNI EN ISO 2812-1:1996 and UNI EN ISO 2812-2:1996)
general methods to determine the resistance of a single paint layer, of a painting cycle or of similar products to fluids. Three test methods can be applied. The method to be used depends on the particular requirements of the tested material: the first method is suitable for more resistant paint products requiring longer exposure times than those tested by the second and third method. These methods allow to determine the effect of the testing fluid on the painted surface and, if applicable, the support deterioration.
This test gives a method to determine the resistance of a film - made up of a paint single layer or of a paint multi-layer obtained after varnishing cycles by means of paints or similar products - to the action of water, by dipping.
Impact test (UNI 8901:1986)
Method to assess the resistance of a paint product film to the failure due to a violent support strain. The method consists in a mechanical test in which a known mass with set shape is dropped on the painted test sample from different heights.
Colour determination
The absolute colour and/or the colour difference of metallic and polymeric samples can be determined through the parameters L*a*b* of CIELab colour space.
Colour change
the tests of accelerated aging, lightfastness or resistance to outside agents often lead to colour changes that can be measured by a spectrophotometer. In this way, the compliance of the surface protection treatment with the requirements can be checked, also in term of colour changes.
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