This is normally evaluated using a wedge bend or T-bend test, with reference to ASTM test methods D3281-84 or D4145-83. A sample of applied and cured coating is bent through 180°, and evaluated for fracture using acidic copper sulphate, which shows a colour change where reaction with the metal has occurred. The sample can be further evaluated through a second, third and fourth 180° bend. This corresponds to bending the substrate and hence the coating over 1, 2 and 3 thicknesses of substrate (i. e. IT, 2T, 3T).

(iv) Pack Test

The applied cans are packed with product, e. g. beer, cola, diet drinks, product simulants, etc. A series of cans are coated, cured, packed with product, sealed and stored for 6 months (12 months in the USA ). Representative samples of the cans on test are opened every month and tested for substrate contamination via the cured film, mainly iron or aluminium pick-up. Generally, this is the only specific evaluation accepted by two piece can manufacturers as conclusive proof of coating integrity.

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