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ISO 4628-4:2016 pdf free

ISO 4628-4:2016 pdf free.Paints and varnishes – Evaluation of degradation of coatings
This part of ISO 4628 specifies a method for assessing the degree of cracking of coatings by comparison with pictorial standards.
ISO 4628-1 defines the system used for designating the quantity and size of defects and the intensity of 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,
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies
ISO 13076, Paints and varnishes一Lighting and procedure for visual assessments of coatings
3 Terms and definitions
For the purposes of this document, the fllwing terms and definitions apply.
3.1 degree of cracking
rating characterizing cracks in a coating in terms of quantity, size, and depth
4 Assessment
Assess the quantity of cracking by reference to Table 1 and using as example Figure 1 or Figure 2, depending on the type of cracking.
NOTE Figure 1 shows cracking without preferential direction and Figure 2 shows cracking in one preferential direction, which occurs with substrates such as wood (“anisotropic” substrates). Other forms of cracking occur, but the principles of assessing the quantity remain the same.
Where the test area exhibits cracks of various sizes, quote as the size rating that of the largest cracks which are numerous enough to be typical of the test area.
If possible, indicate the depth of cracking by reference to the level in the coating system to which the cracks penetrate. A distinction is made between three main types of failure by cracking:
a) surface cracks which do not fully penetrate the top coat (i.e. checking);
b) cracks which penetrate the top coat, the underlying coat(s) being substantially unaffected;
c) cracks which penetrate the whole coating system.
Carry out the assessment under good ilumination, as specified in ISO 13076.ISO 4628-4 pdf download.

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