What is ISO 4628-7 – standard on degradation of coating - chalking about?
Paints and coatings of all types are widely used to provide colour and pleasing aesthetics, and to prevent deterioration of the underlying substrate when exposed to various environments. Besides protection and beauty, however, coatings provide light reflectivity, camouflage surfaces, reflect and absorb heat, and provide a variety of other functions. With exposure to environmental parameters, coating degrades over time. This leads to crack initiation, propagation & delamination. If the coating is overheated, it can lead to loss of mass or decomposition and ingress of aqueous media can lead to change in the chemical composition of the coating as well.
ISO 4628-7 is part of the ISO 4628 series on the assessment and analysis of paint and varnish degradation due to weathering and age. ISO 4628-7 specifies a method suitable, in particular, for rating the degree of chalking on white or coloured exterior coatings and coating systems on rough surfaces (i.e., those having a roughness greater than segment 4 of the reference comparator G as described in ISO 8503-1).
The test method is applicable to coatings and coating systems on mineral substrates, e.g., fibre cement, brick, concrete, and renderings, independent of the structure of the surface. The method can be used quite effectively by experienced operators and is recommended for laboratory use as well as for onsite evaluation.
Note: When a reference to this test method is included in specifications, the test conditions (i.e., weathering method and substrate) must be agreed between the interested parties.
Who is ISO 4628-7 - standard on degradation of coating - chalking for?
ISO 4628-7, the standard on degradation of coating - chalking is useful for:
- Manufacturers of paints and varnishes
- Concerned maintenance teams
- Product development teams
- Quality control teams
Why should you use ISO 4628-7 - standard on degradation of coating - chalking?
Most protective coatings perform well until an old age, at which time natural deterioration and degradation occur. Energy acting on a coating can degrade a material by breaking or interfering with the chemical bonds holding the resin together and to a substrate.
ISO 4628-7 the normative references and terms and definitions along with assessment techniques are discussed in thorough details. Using ISO 4628-7 guidelines, you can evaluate the degradation of coatings and designate the quantity and size of defects, in terms of the intensity of uniform changes in appearance, and the degree of chalking. This helps you to design better products and mitigate weathering challenges for coatings, so that your customers can enjoy long lasting products.
What’s changed since the last update?
BS EN ISO 4628-7:2016 supersedes BS EN ISO 4628-7:2003. BS EN ISO 4628-7:2016 includes some technical changes with respect to BS EN ISO 4628-7:2003. These include:
- The pictorial reference standard for numerical chalking ratings 1 to 5 have been copied from ISO 4628-6:2011
- A normative reference to ISO 13076 for illumination for the assessment has been added
