Passivation method for high-resistance electroplated tin plate

Abstract

The invention discloses a passivation method for a high-resistance electroplated tin plate. The passivation method adopts a production process combining chemical passivation and electrochemical passivation. The electroplated tin plate before passivation is put into a passivation tank A for chemical passivation. After the chemical passivation is completed, the chemically passivated electroplated tin plate is continuously put into a passivation tank B for electrochemical passivation, and the high-resistance electroplated tin plate is obtained. The passivation tank A and the passivation tank B are both filled with a passivation solution which is sodium dichromate with the concentration of 19-26 g / L. In the process of the electrochemical passivation, the passivation power density ranges from 200 C / dm<2> to 400 C / dm<2>. According to the passivation method, the thickness of a passivation film ranges from 4.0 mg / m<2> to 8.0 mg / m<2>, and the mass content of Cr(OH)3 in a passivation film organizational structure ranges from 55% to 65 %, so that the coating quality of the electroplated tin plate is greatly improved, the requirement on product resistance after subsequent coating is improved,and the value of the product coated with the film is effectively increased.

Description

technical field [0001] The invention belongs to the technical field of steel deep processing, and in particular relates to a passivation method for a high-resistance electro-tin plate. Background technique [0002] Electroplated tin plate is an environmentally friendly and safe packaging material, widely used in food cans, beverage cans, aerosol cans, chemical barrels, and various packaging miscellaneous cans. In particular, food cans and luncheon meat have higher requirements for the resistance of the inner coating in the iron printing process, while braised pork cans have higher requirements for the resistance of the inner coating. [0003] At present, none of the electroplated tinplates available in the market can solve the resistance problem of the internal coating of luncheon meat and braised pork, and cannot continuously and stably meet the resistance and adhesion requirements of iron printing, can making, and filling the contents. . The factors affecting the iron re...

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Problems solved by technology

[0003] At present, none of the electroplated tinplates available in the market can solve the resistance problem of the internal coating of luncheon meat and braised pork, and cannot continuously and stably meet the resistance and adhesion requirements of iron printing, can making, and filling the contents.

The factors affecting the iron resistance of coatings include the thickness and structure of the passivation film of the tinplate, the variety and quality of the coating, the baking temperature and curing time, and the thickness of the coating film. The main reason for the unqualified resistance is tin plating. The plate passivation film is not dense enough, and the chromium oxide deposited on the surface of the tinplate has pores, which cannot play a complete isolation role, resulting in the reaction of tin or iron with sulfur atoms in the tinplate to form tin sulfide or iron sulfide , so that sulfur spots appear in the tank

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