The present invention relates to a four-function steel surface treatment liquid and a preparation method thereof, the components of raw materials of the four-function steel surface treatment liquid per liter include: phytic acid of 15 g-18 g, hydroxyethylidene-1, 1-diphosphonic acid of 50 g-65 g, phosphoric acid solution of 280 g-320 g, manganous dihydrogen phosphate of 280 g-360 g, thiourea of 5 g-8 g, surfactant of 3 g-6 g, polyethylene glycol of 1 g-2 g, sodium molybdate of 5 g-8 g, and the remaining of water. The four-function steel surface treatment liquid provided by the present invention has the advantages of a good anti-corrosion property and a safe cleaning process, is simple, high efficiency, environmental protection, no hydrogen embrittlement on a metal substrate, no intergranular corrosion, no harm to human skin, no burning, no explosion, and non-toxic, and can be used repeatedly at a normal temperature.

An improved method for preventing corrosion of magnesium is provided. The method includes providing a magnesium substrate including a native surface layer of nanoporous MgO and Mg(OH).sub.2. The method includes generating a CO.sub.2 plasma at atmospheric pressure, flowing the CO.sub.2 plasma from a nozzle exit as a plasma plume, and exposing the surface film to the plasma plume. The method further includes reacting activated CO.sub.2 gas molecules with the native surface layer by performing an atmospheric CO.sub.2 plasma treatment at room temperature to convert at least a portion of the native surface layer of nanoporous MgO and Mg(OH).sub.2 into a nano-structured to micro-structured MgO/MgCO.sub.3 coating.

An improved method for preventing corrosion of magnesium is provided. The method includes providing a magnesium substrate including a native surface layer of nanoporous MgO and Mg(OH).sub.2. The method includes generating a CO.sub.2 plasma at atmospheric pressure, flowing the CO.sub.2 plasma from a nozzle exit as a plasma plume, and exposing the surface film to the plasma plume. The method further includes reacting activated CO.sub.2 gas molecules with the native surface layer by performing an atmospheric CO.sub.2 plasma treatment at room temperature to convert at least a portion of the native surface layer of nanoporous MgO and Mg(OH).sub.2 into a nano-structured to micro-structured MgO/MgCO.sub.3 coating.

A method for the production of metal sheet including a substrate having two faces, at least one of which is coated with a metal coating including between 0.1 and 10% by weight of Mg and optionally between 0.1 and 20% by weight of Al, the remainder of the metal coating being Zn. The method includes at least the steps of providing a steel substrate having two faces, depositing a metal coating on at least one face hot dipping of the substrate, solidifying the metal coating, applying onto the outer surfaces of the metal coating an aqueous solution having a pH of 7 to 13 and including a magnesium ion complexing agent, for which the dissociation constant pKd of the complexing reaction of the agent with the magnesium is greater than or equal to 2, and to the metal sheet obtainable with this method.

A method for the production of metal sheet including a substrate having two faces, at least one of which is coated with a metal coating including between 0.1 and 10% by weight of Mg and optionally between 0.1 and 20% by weight of Al, the remainder of the metal coating being Zn. The method includes at least the steps of providing a steel substrate having two faces, depositing a metal coating on at least one face hot dipping of the substrate, solidifying the metal coating, applying onto the outer surfaces of the metal coating an aqueous solution having a pH of 7 to 13 and including a magnesium ion complexing agent, for which the dissociation constant pKd of the complexing reaction of the agent with the magnesium is greater than or equal to 2, and to the metal sheet obtainable with this method.

Provided is a film forming method of a corrosion resistant film having a corrosion resistance under acidic atmosphere and a corrosion resistant member on which the corrosion resistant film is coated. The film forming method of the corrosion resistant film includes: bringing a substrate made of aluminum into contact with an aqueous solution containing sulfate ions and fluoride ions; and heating the substrate to boil the aqueous solution on a surface of the substrate and forming a corrosion resistant film containing at least oxygen, fluorine, and sulfur in the aluminum derived from the substrate on the surface of the substrate.

A method for post-treatment of a chromium finish surface to improve corrosion resistance comprising a) providing a substrate having a chromium finish surface, and at least one intermediate layer between the chromium finish surface and the substrate, selected from the group consisting of nickel, nickel alloys, copper and copper alloys, wherein the chromium finish surface is a surface of a trivalent chromium plated layer, obtained by electroplating the substrate, having the at least one intermediate layer, in a plating bath, the plating bath comprising chromium (III) ions; b) contacting the chromium finish surface with an aqueous solution, comprising a permanganate, at least one compound which is selected from a phosphorus-oxygen compound, a hydroxide, a nitrate, a borate, boric acid, a silicate, or a mixture of two or more of these compounds; c) forming a transparent corrosion protection layer onto the chromium finish surface during step b.

Provided is a method for producing an electrode for an electrolytic capacitor, the method comprising: a hydration step in which an aluminum electrode is immersed in a hydration treatment solution having a temperature of 80° C. or higher; and a chemical conversion step in which the aluminum electrode is subjected to chemical conversion treatment up to a formation voltage of at least 400 V. The hydration treatment solution contains a hydration inhibitor. The thickness of a hydrated film formed in the hydration step satisfies the following condition, 0.6≤t2/t1≤1, wherein t1 is the average thickness of the hydrated film formed in a depth range of up to 100 μm from the surface of the aluminum electrode, and t2 is the average thickness s of the hydrated film formed in a deep portion at least 100 μm from the surface of the aluminum electrode.

The present invention addresses the problem of providing, a metal surface treatment agent capable of exhibiting excellent corrosion resistance and excellent coating adhesion in painted metal materials; and a metal surface treatment method using the metal surface treatment agent. The problem is solved by a pretreatment agent that is used in a pretreatment of a chemical conversion treatment performed for forming a chemical conversion coating on/over a surface of a metal material, the pretreatment agent containing: a metal alkoxide (A) containing at least one metal element selected from zirconium, titanium, vanadium, and aluminum; and at least one sulfonic acid (B) selected from methanesulfonic acid, ethanesulfonic acid, hydroxymethanesulfonic acid, and hydroxyethanesulfonic acid. The problem is also solved by a chemical conversion treatment agent that contains a zirconium alkoxide (a) and a zirconium-containing ion supply source (b), and has a pH of 1.5 to 6.5.

A case includes a main body made of a magnesium alloy, and configured to house oil therein. An inner wall surface of the main body is coated with a black film.