Sampling Method

1. Products delivered simultaneously and of the same specification shall be defined as one batch.

2. The batch shall be divided into groups of 20 pieces each. Any remainder fewer than 20 pieces shall also be considered one group.

3. One piece shall be randomly selected from each group as a sample. For batches with fewer than 20 pieces, two pieces shall be selected as samples.

4. From the upper, middle, and lower parts of the sample piece, randomly select 7 sheets from each part, totaling 21 sheets. One sheet is used for physical and chemical performance testing, and the remaining 20 sheets are for appearance inspection.

5. Reinspection
a. Appearance: If the number of defective sheets in any category is greater than or equal to 4, double the sample size from the same group and conduct reinspection. If the reinspection still finds 4 or more defective sheets in any category, the group is deemed to fail the appearance inspection.

b. Physical and Chemical Indicators: If any indicator is non-conforming, double the sample size from the same piece and conduct reinspection. If the reinspection still finds any non-conforming indicator, the group is deemed to fail the physical and chemical inspection.

c. If both appearance and physical/chemical indicators meet the standards, the group is deemed qualified.

d. Defects inherent to the tin-plated (or chromium-plated) thin steel sheet itself, such as tin spots, pitting, white spots, water marks, and surface chromium content not meeting the standard, should not be regarded as printing or coating quality issues.