The present invention relates to methods and compositions for coating ferrous metal substrates. In an embodiment, the invention includes a composition for forming a magnetite coating on a ferrous metal substrate. The composition comprising an aqueous oxidizing solution. The aqueous oxidizing solution comprising an alkali metal hydroxide, an alkanolamine, and a chloride salt. In an embodiment, the invention includes a method of forming a magnetite coating on a ferrous metal substrate. The method including contacting the ferrous metal substrate with an aqueous oxidizing solution, the aqueous oxidizing solution comprising an alkali metal hydroxide, an alkanolamine, and a chloride salt. Other embodiments are also included herein.

The present invention relates to methods and compositions for coating ferrous metal substrates. In an embodiment, the invention includes a composition for forming a magnetite coating on a ferrous metal substrate. The composition comprising an aqueous oxidizing solution. The aqueous oxidizing solution comprising an alkali metal hydroxide, an alkanolamine, and a chloride salt. In an embodiment, the invention includes a method of forming a magnetite coating on a ferrous metal substrate. The method including contacting the ferrous metal substrate with an aqueous oxidizing solution, the aqueous oxidizing solution comprising an alkali metal hydroxide, an alkanolamine, and a chloride salt. Other embodiments are also included herein.

Provided is a method for preparing a metal oxide or a metal hydroxide nano thin-film material by a molten salt method, which mainly comprises the following steps: heating a low-melting-point salt to a molten state, adding a substrate into the molten salt before or after melting for reaction; adding a metal source and continuing the reaction for a period of time; removing the substrate, cooling the substrate to a room temperature, cleaning and drying the substrate to obtain the metal oxide or metal hydroxide nano thin-film material; wherein, the mass ratio of the low-melting-point salt to the metal source is 100-1.5:1. The metal oxide and metal hydroxide nano-film materials with various nano-morphologies prepared by the method of the present application have morphologies that can be regulated and controlled by the types and proportions of the low-melting-point salts and metal sources.

A method of colorizing stainless steel strip involves the continuous surface treatment of stainless steel strip with aqueous suspensions of rare earth oxide nano or micro particles or aqueous rare earth nitrate solutions of nano or micro particles. The surface treatment can be applied by roll coating, spraying or other conventional application techniques. The coated strip is then continuously annealed. The surface treatment can provide a variety of colors. It also improves corrosion resistance of the processed stainless steel strip. Steel strip treated in this manner is suitable for a variety of applications in the building systems, automotive and appliance markets.

Provided is a method for preparing a metal oxide or a metal hydroxide nano thin-film material by a molten salt method, which mainly comprises the following steps: heating a low-melting-point salt to a molten state, adding a substrate into the molten salt before or after melting for reaction; adding a metal source and continuing the reaction for a period of time; removing the substrate, cooling the substrate to a room temperature, cleaning and drying the substrate to obtain the metal oxide or metal hydroxide nano thin-film material; wherein, the mass ratio of the low-melting-point salt to the metal source is 100-1.5:1. The metal oxide and metal hydroxide nano-film materials with various nano-morphologies prepared by the method of the present application have morphologies that can be regulated and controlled by the types and proportions of the low-melting-point salts and metal sources.

A method for finely powdering tungsten powder, which includes: a process for classifying a material tungsten powder into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter; an oxidation process for forming an oxide film on the particle surface of the coarse powder; and an alkali treatment process for removing the oxide film formed in the oxidation process and a natural oxide film formed on the fine powder with an alkali aqueous solution. Also disclosed is a method for producing ultrafine tungsten powder, which includes obtaining tungsten powder having an average particle diameter of 0.04 to 0.4 μm and a BET specific surface area of 5 to 15 m.sup.2/g by the above method for finely powdering.

A method for finely powdering tungsten powder, which includes: a process for classifying a material tungsten powder into a fine powder having a relatively small average particle diameter and a coarse powder having a relatively large average particle diameter; an oxidation process for forming an oxide film on the particle surface of the coarse powder; and an alkali treatment process for removing the oxide film formed in the oxidation process and a natural oxide film formed on the fine powder with an alkali aqueous solution. Also disclosed is a method for producing ultrafine tungsten powder, which includes obtaining tungsten powder having an average particle diameter of 0.04 to 0.4 μm and a BET specific surface area of 5 to 15 m.sup.2/g by the above method for finely powdering.

This coated steel sheet comprises: a steel sheet; a primer coating film that is arranged on the steel sheet and contains a chromic acid-based rust preventive pigment and aggregate that serves as primary particles, while not containing porous particles; and a top coating film that is arranged on the primer coating film. The aggregate satisfies the following formula (1) and formula (2).

D.sub.10≧0.6T (1)

D.sub.90<2.0T (2)

(In the formulae, D.sub.10 represents the 10% particle diameter (μm) of the aggregate in the number-based cumulative particle size distribution; D.sub.90 represents the 90% particle diameter (μm) of the aggregate in the number-based cumulative particle size distribution; and T represents the film thickness (μm) of a portion of the primer coating film, in which the aggregate is not present.)

This coated steel sheet comprises: a steel sheet; a primer coating film that is arranged on the steel sheet and contains a chromic acid-based rust preventive pigment and aggregate that serves as primary particles, while not containing porous particles; and a top coating film that is arranged on the primer coating film. The aggregate satisfies the following formula (1) and formula (2).

D.sub.10≧0.6T (1)

D.sub.90<2.0T (2)

(In the formulae, D.sub.10 represents the 10% particle diameter (μm) of the aggregate in the number-based cumulative particle size distribution; D.sub.90 represents the 90% particle diameter (μm) of the aggregate in the number-based cumulative particle size distribution; and T represents the film thickness (μm) of a portion of the primer coating film, in which the aggregate is not present.)

Disclosed are new boronizing compositions consisting of boron fluoride and boron oxide, borax, or an iron boride. The compositions reduce the heating temperature and time. Further disclosed are methods of boronizing a metal substrate including these compositions, or any combination thereof.