DIN EN ISO 4628-6:2011-12

ISO 4628-6 defines the system for designating the quantity and size of degradation of coatings and the intensity of uniform changes in appearance of coatings and outlines the general principles of the system. This system is intended to be used, in particular, for defects caused by ageing and weathering, and for uniform changes such as colour changes, for example yellowing. The other parts of ISO 4628 provide pictorial standards or other means for evaluating particular types of defect. As far as possible, the information is based on already existing specifications. This part of ISO 4628 provides pictorial standards and a method by which the degree of chalking can be rated. In using this method, it is essential to distinguish between degradation products of the coating and adhering dirt, particularly when chalking is slight. The tape method using a colourless, transparent tape is suitable for both white and coloured coatings. It must be noted that "chalking" is not to be confused with "efflorescence", in which dissolved pigment crystallizes on the surface of the coating without the binder being destroyed. The method given in this draft standard is not intended to cover efflorescence. Where dirt adheres to the surface of coatings exposed to natural weathering, the appearance of the tape may seem to indicate chalking when in fact it is only the layer of dirt that has been lifted off the coating surface. By careful examination of the tape it is relatively easy to distinguish between dirt and chalking pigment. The Committee responsible for this draft standard is NA 002-00-07 AA "Allgemeine Prüfverfahren für Beschichtungsstoffe und Beschichtungen" ("General test methods for coating materials and coatings") at DIN.