ISO 4628-6:2011 pdf free download

07-01-2021 comment

ISO 4628-6:2011 pdf free download.Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 6: Assessment of degree of chalking by tape method.
ISO 4628-1 defines the system for designating the Quantity and size of defects and the intensity of uniform changes of coatings and outlines the general principles of the system. This system is intended to be used, in particular, for defects caused by ageing arid weathering, and for Laliform changes such as coloLK changes, for example ylowing.
The other parts ci ISO 4628 provide pictorial standards or other means for evalualing particuLar types ci defect. As far as possible, already existing evaluation schemes have ben used as the basis.
The chalking scale used in the fIrst (1990) edition and in this third edition ci ISO 4628-6 consists ci photographic pictures of adhesive tapes with different amounts of pigment particles adhering to them. The piiient particles are not evenly distributed over each tape. The lower ratings in particLiar (i.e. I to 3) give the impression of cloudiness All live ratings In the scale used In the fIrst (1990) edition and In this edition are sufficiently different for visual-assessment purposes, however.
The scale used in the second (2007) edItion was computer-generated. Thus the white dots representing the piiient particles were distributed very evenly over the tape, with the result that not all the ratings differed sufficiently well from each other for visual assessment to be carfled out. While ratIngs 0,5 10 3.0 on the black background on the 2007 scale could be differentiated sufficiently wel from each other. It was hardly possible to differentiate visually between ratings above 3,0. especially ratings 4 and 5. On the white background, the difference between ratings 0,5, 1,0 and 1,5 was not easy to discern. The differences between ratings 1,5 to 5.0 were more evident, however
Comparing the 1990 scale with the 2007 scale, it woLid appear that rating I on the 1990 scale corresponded to 0,5 on the 2007 scale, and rating 2 on the 1990 scale corresponded to 1 on the 2007 scale,
It was therefore decided that the 2007 scale was unsuitable for use in the visual assessment of the degree of challung of paints over the whole rating scale from 0,5 to 5,0.
This part of ISO 4628 provides pictorial reference standards for designating the degree of dialking of peril coatings. It also describes a method by wNch the degree of chalking Is rated. In using this method. Ills essential that care be taken to distinguish between true degradation products and adhenng dirt. particularly when chalking Is slight.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
appearance of a loosely adherent fine powder on the surface of a paint coating, arising from the degradation of one or more of its constituents
3 PrincIple
The d’ialking is removed train the coating under test using an adhesive tape. The chalking adhering to the tape examined against a contrasting background (either black or white, whichever gives the greater contrast) and the deee of chalking is assessed with reference to a rating scale.
4 Materials
4.1 Salf.adhslve transparent tap., of width at least 15 mm.
Commeraaly avaiIle flexible tapes, transparent and without perceptible colour, have been found to be satisfactory. However, the quality of the tape aftects the rating obtained. The type of tape shal therefore be agreed on between the interested parties and shall be stated in the test report
4.2 Background, black or Mute, with malt finish, for example card or velvet having a short pile without a tendency to be aushed.
5 Procedure
5.1 Allow the surface to dry at room temperature before carrying out the test.
Place a piece of the adhesive tape (4.1) on the dry coang by applying firm pressure and rubbing with a finger.
The length of the tape should be at least 40 mm.
Remove the tape perpendicularly to the surface and lay it on a background (4.2) of the appropriate colour to give the greater contrast with the adhesive in contact with the background. Assess tight-coloured coatings on the black background and dark-coloured coatings on the white background.
Under consistent il)unwiation. immediately assess (see 5.5) the degree of chalking by comparing the amount of chalk on the tape with the pictorial reference standards in Figure 1. The more background that is visible, the lower the rating. Report the dluminatlon in the test report
52 The degree of chalking may also be determined quantitatively using a suitable photoelectric instrument to compare the transmittance of the chalked tape with that of unused tape. In this procedure, the adhesive tape shall not be placed on a background (4.2) but on a dean glass slide or open support, wtiidl Is placed in the optical beam of the instrument(21.PL A transmittance of less than 70% of that of the unused tape indicates chaadng,
This instrumental method shall only be used if the pattern of chalUng residues on the tape is homogeneous.
5.3 The degree of chalking can vary over a given area. On large areas with a uniform surface (no texture), the determination should preferably be made at several locations and the mean and range reported
Apply the tape to an area of the panel that has not been used for previous measurements to avoid false readings.
5.4 Ratings obtained with coatings exposed to natural weathering shal be treated with caution as dirt deposited on the surface from the atmosphere can give false values of chalking.
5.5 After removing the chalting from the coating under test, the assessment of each piece of adhesive tape shal be carried out without delay because the appearance of the chalking residues on the adhesive tape and the transmittance of the tape might change with time.
5.6 When testing low-gloss paint coatings, a certain amount of loosely adherent material might be observed, even with unweathered panels. A blank test, carried out on an unweathered panel, is therefore recommended for such coatings.
6 Rating
Rate the degree of chalking by reference to the pictorial standards shown in Figure 1.
NOTE The numencal values given asreepond to those in ISO 4628-1
For textured surfaces, the rating shall be based on the observations of the most intensively chalked parts of the tape.
7 Test report
The test report shall contaan at least the followwig information:
a) all information necessary for the identification of the sample tested:
b) areferencelothis partof 1304628 (13046284:2011);
c) details of the method used, induding:
1) the type of weathering (artificial or natural) ol the coating,
2) all details necessary for the identification of the adhesive tape used, including the manufacturer and the name of the tape.
3) all detads necessary for the identification of the substrate used as the background for the adhesive tape (see 42),
4) the ilkjmioalion used for the assessment
d) the results of the test. mciudng:
1) the numerical rating of the degree of chalking.
2) whether the evaluation was carried out visualty or using an instrument (see 52):
e) any deviations from the procedure specified:
f) any unusual features (anomalies) observed during the test:
g) the data of the test.

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