The Process Of Tinplate

The tinplate of tinplate mostly adopts acid plating process, and hot-dip tin plating process can also be used. The surface of the steel plate is silvery-white after electro-tinning, and the thickness of this tin plating is about 0.4~4μm, which is generally expressed by the amount of tin plating per unit area (g/m2) in technology. 

The tin plating layer after tinplate plating has many pores, and the corrosion resistance is not good. Therefore, it is necessary to carry out soft solution treatment or passivation treatment after electroplating to form a tin alloy layer and a tin oxide layer on its surface, respectively. Only by making the coating bright, and enhancing the adhesion between the coating and the steel plate and reducing the porosity, can the corrosion resistance be effectively improved. 

The surface of tinplate is electroplated, mainly because the electrode potential of tin is higher than that of iron, and the chemical properties are stable, so it can play a role in rust protection for steel plates. However, the tin plating must be kept intact, and if it is cut, or even only a tiny pore that exposes the steel base, the steel plate will be corroded quickly due to anodic corrosion. 

The main production process of tinplate is: pickling of low-carbon thin steel plates→ electro-tinning→ soft solution treatment→ passivation treatment→ oiling → inspection→ shearing→ classification → packaging. 

The tinplate plate has been analyzed by metallographic analysis, and its organizational structure has a total of five layers from the inside to the outside. 

1. Steel substrate: generally used for canning, its thickness is 0.2~0.3mm. 

2. Tin-iron alloy layer: It is a tin-iron alloy structure, and the tin content of electro-tinplate is <1g/m2, and the hot-dip tinplate is 5g/m2. 

3. Tin layer: pure tin layer, the amount of tin plating of electroplating tin plate is 5.6g/m2~22.4g/m2, and the amount of tin plating plate is 22.4g/m2~44.8g/m2. 

4. Oxide film layer: mainly stannous oxide, tin oxide, etc. 

5. Oil film layer: cottonseed oil or dioctyl sebacate.