Surface treatment liquid for plated steel sheet to be hot-pressed

Abstract

The invention relates to a surface treatment liquid for a plated steel sheet to be hot-processed. The present invention is a surface treatment liquid with excellent storage stability and is able to provide a surface-treated steel sheet for which the treatment coating formed has excellent water resistance, solvent resistance, adhesion to plated steel sheets, and hot lubricity as well as chemical conversion treatability after hot-pressing, corrosion resistance after coating, and spot weldability. The surface treatment liquid for a plated steel sheet that is to be hot-pressed comprises an aqueousZnO dispersion (A) and a water-dispersible organic resin (B). The aqueous ZnO dispersion (A) comprises water and ZnO particles, the particle diameter of which is 50-300 nm. The water-dispersible organic resin (B) has an acid value of 5-45 mg KOH / g and 5-300 nm emulsion particle diameter. The mass ratio (WA / WB) of the mass (WA) of ZnO particles in the aqueous ZnO dispersion to the mass (WB) of solids of the water-dispersible organic resin is 30 / 70 to 95 / 5.

Description

technical field [0001] The present invention relates to a surface treatment liquid excellent in water resistance, solvent resistance, and adhesion to a plated steel sheet of a film. Background technique [0002] In recent years, there has been an increasing demand to suppress the consumption of chemical fuels for environmental protection and prevention of global warming, but this demand has affected various manufacturing industries. For example, automobiles, which are indispensable in everyday life and activities as a means of mobility, are required to improve fuel economy by reducing the weight of the vehicle body. However, in the case of automobiles, it is not possible to simply reduce the weight of the vehicle body in terms of product quality, and it is necessary to ensure appropriate safety. [0003] Many structures of automobiles are made of iron, especially steel plates, and reducing the mass of the steel plates is important for reducing the weight of the car body. H...

AI Technical Summary

Problems solved by technology

[0013] However, in Patent Document 1, a water-soluble resin, a silane coupling agent, etc. are used as a binder for the wurtzite type compound ZnO particles, so the water resistance and solvent resistance of the film are poor, and the adhesion to the Al-coated steel sheet is poor. Insufficient compatibility

Therefore, it is not possible to stably exhibit thermal lubricity, chemical conversion treatment properties after hot pressing, and corrosion resistance after coating with respect to the site where the ZnO film has fallen off.

Moreover, since the stability of the ZnO particles in the treatment liquid is insufficient, the ZnO particles are easily aggregated and precipitated, and the productivity is reduced.

Images