GB/T 41899-2022General quality requirements for coated tinplate and ECCS used in food container (English PDF)

3.1 Intro-plate coating thickness deviation

Intro-plate coating thickness deviation refers to the extreme difference in the coating thickness of the entire coated tin-plated (or chromium) steel sheet.

3.2 Tin melting

Tin melting refers to the difference in tin metal color and luster that occurs after the tin layer of a steel sheet is melted.

3.3 Burnt

Burnt refers to the burning of the coating film caused by excessively high temperatures.

3.4 Wax incorporation

Wax incorporation refers to a phenomenon of wax precipitation on the surface of the coating film.

3.5 Spot

Spot refers to a phenomenon of uneven coating and spots.

3.6 Flaking

Flaking refers to a phenomenon where the coating film is cracked or peeled off and separated from the substrate.

3.7 Sticky plate

Sticky plate refers to a phenomenon of bonding together during the process of coating and printing.

3.8 Dirt

Dirt refers to a substance other than paint adhered to the coating film.

3.9 Dust contaminated

Dust contaminated refers to a phenomenon of dust contamination of coated tin-plated or chromium-plated steel sheet.

3.10 Edge effect

Edge effect refers to a phenomenon of paint accumulation on the coating film on the upper edge of the plate.

3.11 Curtain; runs; sags

Curtain; runs; sags refer to a phenomenon of paint accumulation on the coating film on the vertical plate.

3.12 Missing coat

Missing coat refers to a phenomenon of incomplete coating film on the steel plate.

3.13 Poor level ling

Poor levelling refers to a phenomenon of uneven coating film or surface roughening on the coated tin-plated or chromium-plated steel sheet.

3.14 Dipping

Dipping refers to the phenomenon of dipping paint on the steel plate during the process of coating and printing.

3.15 Contaminated mark

Contaminated mark refers to stains that appear when the coated tin-plated or chromium-plated steel sheet is contaminated.

3.16 Mark caused by damaged coating roller

Mark caused by damaged coating roller refers to traces of defects on the coating film due to the damage of the coating roller during the process of coating and printing.

4.1 Raw Materials and Accessories

4.1.1 Tin-plated or chromium-plated steel sheet

Tin-plated steel sheet shall comply with the stipulations of GB/T 2520 and the requirements of relevant standards; chromium-plated steel sheet shall comply with the stipulations of GB/T 24180 and the requirements of relevant standards.

4.1.2 Coating

The used coating, for example, enamel or varnish, shall comply with the stipulations of relevant standards.

4.1.3 Other accessories

Other accessories shall comply with the stipulations of relevant standards.

4.2 Technical Requirements

4.2.1 Appearance

4.2.1.1 The coating film shall be smooth and flat, with consistent color and luster, and without S---the area of the sample piece, expressed in (mm2).

5.5.2 Method 2: instrument method

5.5.2.1 Equipment requirements

Electronic thickness gauge, with an accuracy of 0.1 g/m².

5.5.2.2 Test procedures

5.5.2.2.1 Select a large flat coated and printed metal sheet with a uniform and complete coating film; use the electronic thickness gauge to conduct the measurement. During the measurement, find two measurement points M1 and M2 with the same reading on the iron sheet; cut out two marked coated and printed metal sheets: adopt the method of electrolytic film removal on M1 to measure its dry film thickness; mark the coating film thickness of M1 sample plate as the standard value of the coating film of M2 sample plate.

5.5.2.2.2 Before beach measurement of the sample, based on the value of the standard plate, perform the calibration.

5.5.2.2.3 In order to ensure the validity of the standard plate, the replacement cycle of the standard plate is 1 month. When the standard plate is worn or affects the measurement accuracy, it shall be replaced in time.

5.5.2.2.4 Use the calibrated electronic thickness gauge to carry out the test on the entire coated and printed metal sheet to obtain the maximum and minimum values.

5.5.2.3 Result calculation

The result directly read by the electronic thickness gauge is the thickness of the coating film.

The intro-plate coating thickness deviation of the coating film thickness is the difference between the maximum value and the minimum value of the coating film thickness on the entire coated and printed metal sheet.

5.6 Adhesion

5.6.1 Requirements for tape

Adhesive tape with an adhesive force of (47 ± 3) N/100 mm.

5.6.2 Requirements for equipment

A paint film circle-drawing tester that complies with the requirements of 4.1 in GB/T 1720-2020. The screw pitch of the test bench is 1.5 mm; the load is 500 g; the standard turning radius of the rotating needle is 5.25 mm.

5.6.3 Test procedures

Refer to the position marked 2 in Figure 1 to cut a 100 mm x 50 mm printed specimen; at a 1---sample plate; 2---flat mold; 3---weight; 4---steel ball; F---tensile force.

5.6.6.2 Test procedures

Refer to the position marked 13 in Figure 1 to take three specimens of 210 mm x 110 mm, with the test surface facing upward; test its dynamic friction coefficient.

5.6.7 Hardness of coating film

In accordance with the instrument and method specified in GB/T 6739, conduct the test.

5.6.8 Curing properties of internal and external coating films

5.6.8.1 Repeatedly fold the sample pieces into cubes with a spacing of 3 mm; immerse two sample pieces in an inert container filled with distilled water; place the other two sample pieces in an inert container without adding water.

5.6.8.2 Place the test container in a sterilization pot; select the test conditions in accordance with 5.3. After natural depressurization and cooling, take out the sample pieces. Observe the condition of the coating film.

5.6.9 Anti-acid

5.6.9.1 Preparation of citric acid solution (20 g/L)

Weigh-take 20.0 g of citric acid, use water to dissolve it and reach a constant volume of 1,000 mL, and shake it well; reserve it for later use.

5.6.9.2 Preparation of acetic acid solution (30 mL/L)

Measure-take 30 mL of glacial acetic acid, dilute to a constant volume of 1,000 mL, and shake it well; reserve it for later use.

5.6.9.3 Test procedures

5.6.9.3.1 Repeatedly fold the coated tin-plated (chromium) steel sheet into cubes with a spacing of 3 mm, and immerse them in an inert container filled with the test solution of 5.6.9.1; seal it with a cover. The distance between the test solution and the inner surface of the cover of the container shall be 5 mm ~ 7 mm.

5.6.9.3.2 Repeatedly fold the coated tin-plated (chromium) steel sheet into cubes with a spacing of 3 mm and immerse them in an inert container filled with the test solution of 5.6.9.2; seal it with a cover; there shall be no leakage of the test solution. The test solution shall be 5 mm ~ 7 mm away from the inner surface of the cover of the container (this test item is only used when the content of the final product contains acetic acid).

5.6.9.3.3 Put the test container in a pressure cooker; in accordance with 5.3, select the test conditions. After natural depressurization and cooling, take out the sample pieces; wash and dry them. Observe the condition of the coating film.

5.6.10 Sulfur resistance

5.6.10.1 Preparation of mixed solution of L-cysteine hydrochloride (0.5 g/L), potassium dihydrogen phosphate (3.6 g/L) and disodium hydrogen phosphate (7.2 g/L)

Weigh-take 0.50 g of L-cysteine hydrochloride (C3H8NO2SCl) or 0.56 g of L-cysteine hydrochloride (C3H8NO2SCl - H2O), 3.60 g of potassium dihydrogen phosphate and 18.0 g of disodium hydrogen phosphate (Na2HPO4 - 12H2O); respectively use water to dissolve them, then, mix them and dilute to 1,000 mL. The mixed solution shall be used within 4 h after preparation.

5.6.10.2 Test procedures

5.6.10.2.1 Repeatedly fold the sample piece into cubes with a spacing of 3 mm and immerse them in an inert container filled with the test solution of 5.6.10.1; seal it with a cover; there shall be no leakage of the test solution. The test solution shall be 5 mm ~ 7 mm away from the inner surface of the cover of the container.

5.6.10.2.2 Put the test container in a pressure cooker; in accordance with 5.3, select the test conditions. After natural depressurization and cooling, take out the sample pieces; wash and dry them. Observe the condition of the coating film.

5.6.11 Salt resistance

5.6.11.1 Preparation of sodium chloride solution (with a mass fraction of 3%)

Weigh-take 30 g of sodium chloride, add 970 g of water, dissolve and shake it well; reserve it for later use.

5.6.11.2 Test procedures

Repeatedly fold the sample piece into cubes with a spacing of 3 mm, add the test solution in 5.6.11.1 and seal it. In accordance with 5.3, select the test conditions. After natural depressurization and cooling, take out the sample pieces; wash and dry them. Observe the condition of the coating film.

5.6.12 Alkaline resistance

5.6.12.1 Preparation of sodium bicarbonate solution (20 g/L)

Audio universal bridge, with a test accuracy of 0.1%.

5.6.15.3 Test procedures

5.6.15.3.1 Cut five sample pieces (or circular test pieces with an area of 25 cm²) of 50 mm x 50 mm with intact surface and no trace of damage; install them on the fixture for the corrosion resistance test.

5.6.15.3.2 Inject the test solution of 5.6.15.1 into the test fixture, make the tested surface of the test piece fully contact with the solution, and keep it full for 24 h.

5.6.15.3.3 Turn on the audio universal bridge, select (CP - D) test item; set the test parameters as frequency 1,000 Hz, voltage 100 mV. It is advisable to read the value of the audio bridge after it stabilizes for 1 min.

5.6.15.3.4 Scrape the coating film on the edge of the test piece, and connect it to one electrode of the digital bridge. Connect the other electrode of the digital bridge to the electrode on the test fixture opposite to the test piece.

5.6.15.3.5 After the reading displayed on the instrument is stable, read the capacitance CP and dielectric loss tangent D; discard the maximum and minimum values from the results, and take the arithmetic mean of the remaining three test pieces to represent the capacitance value CP and dielectric loss of the sample; the test pieces of other sizes are converted in accordance with 25 cm², and the capacitance value is directly proportional to the area.

6.1 Batch

The inspection shall be carried out in accordance with the batch or group of products. The products of the same specification and delivered at one time shall be a batch. Through negotiation between both parties, the same batch of products can be divided into several groups, which shall be packages of integer multiples.

6.2 Classification of Inspection

Each batch of products shall be inspected by the inspection department of the manufacturer, and can only exit the factory after passing the inspection of 4.2.1 ~ 4.2.14. In addition, a product quality certificate shall be issued.

6.3 Inspection Items

The products shall be subject to the acceptance inspection in groups.

6.4 Sampling Schemes

6.4.1 Every 20 products in the same batch are determined as a group, and the remainder of less than 20 products is also considered as a group.

6.4.2 From each group, randomly take one piece as a test piece. When there are less than 20 products in a group, take two pieces as test pieces.

6.4.3 Randomly take 21 samples from the test piece. One of them is used for performance requirements inspection, and the remaining 20 are used for visual inspection.

6.5 Determination Rules

6.5.1 If the number of disqualified samples in one item (or more than one items) is greater than or equal to 4, double the sampling size from the same group and conduct a re-inspection. If the re-inspection results still show that the number of disqualified samples in one item is greater than 4, then, the group shall be determined as disqualified in appearance.

6.5.2 If the inspection results show that one (or more than one) indicator is disqualified, double the sampling size from the same test piece to conduct a re-inspection. If there is still one disqualified item in the re-inspection results, then, the group shall be determined as disqualified in physical and chemical indicators.

6.5.3 When the appearance and physical and chemical indicators are all qualified, then, the group shall be determined as qualified.

6.5.4 The possible defects of the tin-plated (or chromium) steel sheet, such as: tin spots, pocking marks, white spots, water spots, and surface chromium content that do not comply with this document, shall not be considered as printing and coating quality problems.

7.1 Marking

The outer packaging of the product shall have a product inspection certificate and a packing list, and the content shall include: the mark and name of the manufacturer, product name, product specifications, production No., production date and quantity.

7.2 Packaging

7.2.1 The packaging shall satisfy the integrated packaging and transportation requirements, and the packaging materials shall be clean, and free from peculiar smell and contamination, etc.

7.2.2 The packaging shall comply with the stipulations of relevant standards.

7.2.3 Each product shall be firmly bundled from the outside, and for easy transportation, the original packaging should be adopted.

7.2.4 In wet seasons, when necessary, raw and auxiliary materials and products that are easily affected by moisture shall take moisture-proof measures or packaging, so as to prevent moisture […]