In order to check whether the ink on the surface of the tea tin box is qualified, one of the most common and easy to master methods is the liquid tension and casting test of the paint. Just take a small amount of paint and slowly invert it on the surface of the flat tinplate. Observe the flow direction of the paint carefully. If the coating liquid spreads rapidly around, and the center point of the liquid is roughly equal to the radius of the surrounding wetting, then the tinplate will be lifting one end makes the tinplate at a 45-degree angle to the plane. If the liquid flows evenly to the other end, this means that the ink meets the printing requirements of the tea tin box. If the coating does not condense on the surface of the tinplate or spread irregularly around, it means that the ink quantity does not meet the requirements of this printing. The tinplate also needs to be baked before printing.
The second layer of the surface structure of the tea tin box is an oxide film. After the tinplate tinning process is completed, a very thin oxide film is formed on the surface of the tin. Its composition is generally divalent tin or tetravalent tin oxides and hydrates, and the structure is relatively unstable. Many people think that the thinner the oxide film, the better its adhesion, and vice versa. In fact, this argument still has some truth, because the tinplate needs to be passivated after tin plating. The purpose of the passivation treatment is to make the surface of the tinplate more stable and prevent the surface oxide film from continuing to grow. Excessive oxide film can cause the tinplate to change color during long-term storage, especially after printing and baking. Moreover, due to the structural instability, the ink layer on the oxide film is peeled off, resulting in the loss of adhesion of the ink, which leads to quality problems in the production of the finished product.
The surface of the plated tinplate is usually chemically or electrochemically passivated, and the hot-dip tinplate is not passivated during the production process. Therefore, the manufacturer must make the tea tin box according to the shape of the product. , mechanical processing characteristics, etc., choose the appropriate tinplate material.