introduction
ISO (International Organization for Standardization) is a global alliance of national standards bodies (ISO member bodies). The development of international standards is usually carried out through ISO technical committees. Each member institution interested in a subject on which a technical committee has been established has the right to be represented on that committee. International governmental and non-governmental organizations liaising with ISO are also involved in this work. ISO works closely with the International Electrotechnical Commission (IEC) on all matters of electrical standardization.

International standards are drafted in accordance with the rules given in Part 2 of the ISO/IEC Directive.

The main task of the technical committee is to develop international standards. The draft international standard adopted by the Technical Committee will be circulated to the member bodies for voting. Publication as an international standard requires approval by at least 75% of member institutions.

ISO 4628-6-2011 Assessment of the number and size of defects and the intensity of uniform changes in appearance in paints and varnishes coatings for ageing – Part 6: Assessment of the degree of chalking by the tape method

Please note that certain elements of this document may be subject to patent rights. ISO is not responsible for identifying any or all such patents.

ISO 4628-6 was developed by Technical Committee ISO/TC 35, Paints and varnishes, Sub-Committee SC 9, General Test Methods for paints and varnishes.

The third edition cancels and replaces the technically revised second edition (ISO 4628-6:2007). The main changes are as follows:

a) The graphic standard (photographic picture) used in the first edition (ISO 4628-6:1990) has been reinserted because the computer-generated chalk scale used in the second edition (ISO 4628-6:2007) does not always give the same rating as the scale used in the first edition (see introduction for more details);

b) Increased the limit of tape transmission, below which powdering is considered to have occurred (see 5.2).

ISO 4628 consists of the following parts under the general heading: Paints and varnishes – Assessment of coating degradation – Designation of the number and size of defects, and the intensity of uniform changes in appearance:

ISO 4628-6-2011 Assessment of the number and size of defects and the intensity of uniform changes in appearance in paints and varnishes coatings for ageing – Part 6: Assessment of the degree of chalking by the tape method

– Part 1: General introduction and specification of the system

– Part 2: Assessment of the degree of foaming

– Part 3: Assessment of the degree of rust

– Part 4: Evaluation of degree of cracking

– Part 5: Assessment of the degree of spalling

– Part 6: Evaluation of pulverization by tape method

– Part 7: Evaluation of pulverization by velvet method

– Part 8: Assessment of the degree of delamination and corrosion around lines or other artificial defects

– Part 10: Assessment of the degree of filamentous corrosion

introduce
ISO 4628-1 defines a system for specifying the number and size of defects and the intensity of uniform variation of coatings, and Outlines the general principles for this system. The system is particularly suitable for defects caused by aging and weathering, as well as uniform changes, such as color changes, such as yellowing.

Other parts of ISO 4628 provide graphical standards or other methods for assessing specific types of defects. Build on existing evaluation plans wherever possible.

The chalk scale used in the first (1990) and third editions of ISO 4628-6 consists of a photographic picture of tape adhering to different numbers of pigment particles. The pigment particles are unevenly distributed on each piece of tape. In particular, lower ratings (i.e., 1 to 3) give the impression of being cloudy. However, all five levels in the scale used in the first edition (1990) and this edition differ enough to allow for visual assessment.

ISO 4628-6-2011 Assessment of the number and size of defects and the intensity of uniform changes in appearance in paints and varnishes coatings for ageing – Part 6: Assessment of the degree of chalking by the tape method

The scale used in the second edition (2007) was computer generated. As a result, white dots representing pigment particles are distributed very evenly across the tape, and the results are not all ratings different enough from each other for visual evaluation. While ratings 0,5 to 3 on the black background of the 2007 grade can be well distinguished from each other, it is almost impossible to visually distinguish ratings above 3, 0, especially ratings 4 and 5. On a white background, the difference between ratings 0,5, 1,0, and 1,5 is not easy to discern. However, the difference between ratings 1,5 and 5,0, is more pronounced.

Comparing the 1990 grade with the 2007 grade, a grade 1 in the 1990 grade appears to correspond to a grade 0.5 in 2007, and a grade 2 in the 1990 grade corresponds to a grade 1 in 2007.

Therefore, it was decided that the 2007 Scale was not suitable for visually assessing the degree of paint powdering across the entire grade scale from 0,5 to 5,0.

Important – In order to assess the degree of pulverization by tape method, it is necessary to use the graphic reference standard included in this part of ISO 4628. Since electronic copies of these standards may change when viewed on screen or printed, it is recommended to use only the graphic standards included in printed copies of this part of ISO 4628 purchased from ISO member bodies or their distributors when comparing test results.

ISO 4628-6-2011 Assessment of the number and size of defects and the intensity of uniform changes in appearance in paints and varnishes coatings for ageing – Part 6: Assessment of the degree of chalking by the tape method

1 Range
This part of ISO 4628 provides a graphical reference standard for specifying the degree of powderization of paint coatings. It also describes a method to assess the degree of pulverization. When using this method, care needs to be taken to distinguish between true degradation products and adhered dirt, especially in the case of slight powderization.

2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

2.1 Pulverization

The surface of the paint coating appears to be loosely adhered to fine powder, which is caused by the degradation of one or more components

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