White-powder-free erasable zinc-series phosphatizing agent and preparation method

Abstract

The invention discloses a white-powder-free erasable zinc-series phosphatizing agent. The white-powder-free erasable zinc-series phosphatizing agent comprises the following raw materials in percentage by mass: 8 to 28% of phosphoric acid with mass concentration of 85%, 6 to 14% of nitric acid with mass concentration of 65%, 5 to 15% of zinc oxide, 1 to 4% of sodium bromate, 0.1 to 1% of citric acid, 0.1 to 1% of phytic acid with mass concentration of 50%, 0.5 to 2.5% of sodium hexametaphosphate, 0.5 to 2.5% of diammonium hydrogen phosphate, 0.05 to 0.10% of hydroquinone, 0.1 to 0.5% of ferric nitrate, 1 to 1.5% of ethylene glycol monobutyl ether, 1 to 1.5% of special surface active agent for soak degreasing, and the balance of water. The preparation method comprises the following steps in sequence: adding weighed water to a stainless steel reacting kettle; slowly and sequentially adding phosphoric acid, nitric acid and zinc oxide to the reacting kettle; slowly adding citric acid, phytic acid, sodium bromate, sodium hexametaphosphate, diammonium hydrogen phosphate, hydroquinone, ferric nitrate, ethylene glycol monobutyl ether and special surface active agent for soak degreasing to the reacting kettle; and continuously stirring until the solution appears as light beige and transparent liquid.

Description

technical field [0001] The invention relates to a special phosphating agent before metal spraying and its preparation method, especially a phosphating film layer with simple operation and fast film forming speed, which can form a phosphating film layer on the metal surface that is firmly combined with the metal matrix and has uniform crystal thickness. A wiping-type zinc-based phosphating agent that does not generate white powder residue and a preparation method thereof. Background technique [0002] Before the metal is sprayed and painted, its surface must be converted to make it form a conversion film. The conversion film is porous, uniform and fine, and the coating penetrates into the pores to effectively increase the adhesion of the sprayed coating, thereby improving the corrosion resistance of the metal. The conversion film includes phosphating film, passivation film, organic film, rare earth conversion film and sol silane film, etc. The phosphating film is made by imm...

AI Technical Summary

Problems solved by technology

Most of the existing bus body shells are made of combined welding of cold-rolled steel plates with a thickness of 1.5~2 mm. Due to the large body, the phosphating treatment process before spraying and coating cannot realize the automatic line of tank immersion or spraying. Wipe-type phosphating agent

However, the existing wipe-type phosphating agent will produce a large amount of white powder residue that is difficult to remove on the surface of the cold-rolled steel plate after phosphating treatment, which seriously affects the surface quality of the sprayed coating layer.