GB/T 1766-2008Paints and Varnishes – Rating Schemes of Degradation of Coats (English PDF)

3.1 Classification

This Standard uses figures 0 to 5 to rate the damage degree and quantity. “0” shows no damage, and “5” shows serious damage. Determination of four grades by figures 1, 2, 3 and 4 shall make the whole grading range to obtain the best partition zone. If necessary, half grade in the middle can be applied to record more detailed damage phenomenon observed. 3.2.1 Rate visible uniform damage on the coating surface, and rate with damage change degree, as shown in Table 1. 3.2. […]

3.3 Expression method

The expression method shall include the following content: Damage type: grade of damage degree or damage quantity. If it is necessary to indicate damage size grade, it shall be shown in the bracket and add letter “S” before the grade. […]

4.2 Rating of colour changing degree

4.2.1 Instrument determination method

Total colour difference value (∆E*) among sample plates shall be determined and calculated in accordance with GB/T 11186.2 and GB/T 11186.3 before and after aging; see Table 5 for the grade based on colour difference.

4.2.2 Visual colorimetric method

When instrument method is not applicable for determination because the film surface is uneven OR there are 2 or more types of colors on the film surface, then it should use the visual colorimetric method.

Colorimetry shall be conducted BETWEEN the sample plate after aging AND the sample plate without aging (standard plate) in accordance with provisions of GB/T 9761; rating shall be carried out according to colour change degree before and after aging, with reference to GB 250 Gray Scale for Assessing Change in Colour, as shown in Table 6.

4.3 Rating of pulverization grade

4.3.1 Rating of pulverization grade by swan flannelette method is conducted according to ISO 4628-7; see Table 7 for pulverization degree and grade.

1 Very slightly, a trace amount of pigment particles noticeable on the testing cloth.

2 Slightly, a few amount of pigment particles stained on the testing cloth.

3 Obviously, more pigment particles stained on the testing cloth.

4 Rather seriously, a plenty of pigment particles stained on the testing cloth.

5 Seriously, full of pigment particles on the testing cloth, or sample plate exposed the base.

4.3.2 Rating of adhesive tape paper method for pulverization grade shall be carried out according to ISO 4628-6.

Note: rating of ISO 4628-6 adhesive tape paper method for pulverization grade is more applicable for final rating.

4.5 Rating of blister grade

4.5.1 Blister grade of film is expressed by film blister density (see Table 10) and blister size (see Table 11).

4.5.2 Rating expression method of blister grade: blister density grade and blister size grade (with bracket).

For example: blister 2(S3), indicates that blister density is grade 2, and blister size is grade S3.

4.10 Rating of bronzing grade

Grade of coating bronzing is expressed by bronzing degree (see Table 20).

6.2 Record each type of damage phenomenon.

6.3 Record and describe if the film has other abnormal phenomenon except for the above 11 items.

6.4 If the film has several damages phenomenon, it shall be rated according to the most serious item when conducting the comprehensive grade rating.