ISO 28199-2:2021 pdf free download – Paints and varnishes一Evaluation of properties of coating systems related to the spray application process一 Part 2: Colour stability, process hiding power, re-dissolving, overspray absorption, wetting, surface texture and mottling.
In many areas (e.g. car manufacture, industrial coatings, coatings for plastics) the coating materials used are adapted to the specific application equipment and technologies of the particular user. A coating material is, therefore, to be understood as a semi-manufactured product that only receives its final form in combination with the specific application conditions. The adaptation to the application conditions is therefore decisive for the quality of the coated product.
The test methods specified in the Iso 28199 series are based on studies by a Working Group of the European Council for Automotive R&D (EUCAR).
They may be used for evaluation of coating materials in research, development and production with regard to their suitability and safety for industrial processes, and error analysis. The properties of coating materials and coatings to be evaluated depend on the film thickness, so a coating system of increasing thickness is applied to a test panel under defined conditions.
The following characteristics are measured (see ISO 28199-1):
— film thickness in accordance with ISO 2808;
— surface texture;
— colour in accordance with ISO 183 14-1;
— mottling;
— gloss in accordance with ISO 2813.
In combination with visual assessment, the following properties are determined:
— colour stability, process hiding power, re-dissolving, overspray absorption, wetting, surface texture and mottling (this document);
— tendency to sagging, formation of bubbles, pinholing and hiding power (see ISO 28 199-3).
6 Re-dissolving
6.1 General
Re-dissolving is determined by evaluation of the values measured for the constant-thickness base coat and applied wedge-shaped clear coat, obtained in accordance with ISO 28 199-1:2021, 9.4.
For a given drying/application process it is possible that, above a certain film thickness, insufficient solvent escapes. The top layer of the base coat will interact with the solvents of the clear coating material, which is applied later. This could lead to another arrangement of, for example, effect pigments, which can result in greater local differences of the colour space values at the same film thickness.
7 Overspray absorption
7.1 General
Overspray absorption is determined by evaluation of the values measured for the wedge-shaped base coat that was applied (twice) and for the constant-thickness clear coat, obtained in accordance with
ISO 28199-1:202 1, 9.4.
7.2 Evaluation
Using the values measured for the applied wedge-shaped base coat and constant-thickness clear coat, obtained in accordance with ISO 28199-1:2021, 9.4, plot the lightness value L*25 (see ISO 18314-1) against the film thickness of the base coat. Figure 5 shows an example of lightness (L*) plotted against film thickness.
Good overspray absorption occurs when the first and second spraying stages merge with each other.
This results in a steady transition from the plateau of the colour stability to the re-dissolving range (see
Figure 5).
Insufficient overspray absorption is characterized by a large number of measured points occurring in at least two areas.