The amount of wash water to be consumed in an electrodeposition coating facility and the amount of used wash water to be discharged that requires post-treatment are reduced. To achieve this object, an electrodeposition coating facility that includes a degreasing process section A, a post-degreasing rinse section B, a chemical conversion process section C, a post-chemical-conversion rinse section D, an electrodeposition coating section E, and a post-electrodeposition rinse section F is provided with a filtration process apparatus 4 and a wash water recycling line 5. The filtration process apparatus 4 performs a filtration process on wash water W after being used to wash an object to be coated 1 in the post-electrodeposition rinse section F. The wash water recycling line 5 feeds, to the post-chemical-conversion rinse section D, the wash water W after being subjected to the filtration process in the filtration process apparatus 4 as wash water W to be used to wash an object to be coated in the post-chemical-conversion rinse section D.

A conversion coating applicator includes a first liner, a hydrogel attached to the first liner, and a second liner removably attached to the hydrogel. The hydrogel includes a trivalent chromium conversion coating solution including a trivalent chromium compound, a zirconate compound, and a dye compound. The conversion coating solution is an aqueous solution.

A conversion coating applicator includes a first liner, a hydrogel attached to the first liner, and a second liner removably attached to the hydrogel. The hydrogel includes a trivalent chromium conversion coating solution including a trivalent chromium compound, a zirconate compound, and a dye compound. The conversion coating solution is an aqueous solution.

There are provided a ferrite stainless steel for a polymer fuel cell separator having excellent corrosion resistance and interfacial contact resistance under an operating environment of a polymer fuel cell, and a preparation method of the stainless steel. A stainless steel includes C: 0.02 wt % or less, N: 0.02 wt % or less, Si: 0.4 wt % or less, Mn: 0.2 wt % or less, P: 0.04 wt % or less, S: 0.02 wt % or less, Cr: 25.0 to 32.0 wt %, Cu: 0 to 2.0 wt %, Ni: 0.8 wt % or less, Ti: 0.5 wt % or less, Nb: 0.5 wt % or less, waste Fe and inevitably contained elements. A preparation method of the stainless steel having a second passive film formed on a surface thereof includes forming a first passive film on the surface of the stainless steel by bright-annealing or annealing-pickling the stainless steel; removing the first passive film by pickling the stainless steel in a 10 to 20 wt % sulfuric acid solution at a temperature of 50 to 75° C. for a predetermined time; water-washing the stainless steel; and forming the second passive film by performing a passivation treatment on the stainless steel in the mixture of a 10 to 20 wt % nitric acid and a 1 to 10 wt % fluorine acid at a temperature of 40 to 60° C. for the predetermined time. Accordingly, it is possible to prepare a stainless steel having reduced elution resistance and excellent corrosion resistance and to produce a stainless steel for a polymer fuel cell separator, which has low interfacial contact resistance and excellent long-term performance even under a fuel cell operating condition of 60 to 150° C. and various surface roughness conditions.

There are provided a ferrite stainless steel for a polymer fuel cell separator having excellent corrosion resistance and interfacial contact resistance under an operating environment of a polymer fuel cell, and a preparation method of the stainless steel. A stainless steel includes C: 0.02 wt % or less, N: 0.02 wt % or less, Si: 0.4 wt % or less, Mn: 0.2 wt % or less, P: 0.04 wt % or less, S: 0.02 wt % or less, Cr: 25.0 to 32.0 wt %, Cu: 0 to 2.0 wt %, Ni: 0.8 wt % or less, Ti: 0.5 wt % or less, Nb: 0.5 wt % or less, waste Fe and inevitably contained elements. A preparation method of the stainless steel having a second passive film formed on a surface thereof includes forming a first passive film on the surface of the stainless steel by bright-annealing or annealing-pickling the stainless steel; removing the first passive film by pickling the stainless steel in a 10 to 20 wt % sulfuric acid solution at a temperature of 50 to 75° C. for a predetermined time; water-washing the stainless steel; and forming the second passive film by performing a passivation treatment on the stainless steel in the mixture of a 10 to 20 wt % nitric acid and a 1 to 10 wt % fluorine acid at a temperature of 40 to 60° C. for the predetermined time. Accordingly, it is possible to prepare a stainless steel having reduced elution resistance and excellent corrosion resistance and to produce a stainless steel for a polymer fuel cell separator, which has low interfacial contact resistance and excellent long-term performance even under a fuel cell operating condition of 60 to 150° C. and various surface roughness conditions.

Provided is a magnesium-containing metal material that includes coatings having excellent corrosion resistance on a surface. Specifically, provided is a magnesium-containing metal material with coating, which is characterized by including: a magnesium hydroxide-containing first coating on a surface of a magnesium-containing metal material composed of magnesium or a magnesium alloy; a hydroxyapatite and/or hydroxyapatite carbonate-containing third coating over the first coating; and a dibasic calcium phosphate-containing second coating between the first coating and the third coating.

To provide a sanitary facility member having excellent ease of contamination removal and excellent persistence of ease of contamination removal. A sanitary facility member including: a base material, at least the surface of which includes a metal element; a metal oxide layer formed on the surface of the base material; and an organic layer provided on the metal oxide layer; wherein the metal element is at least one element selected from the group consisting of Cr, Zr, and Ti, the metal oxide layer includes at least the metal element and an oxygen element, and the organic layer is bonded to the metal oxide layer by bonding (M-O—P bonding) of the metal element (M) and a phosphorus atom (P) of at least one group (X) selected from a phosphonic acid group, a phosphoric acid group, and a phosphinic acid group via an oxygen atom (O), the group X being bonded to a group R (where R is a hydrocarbon or a group having an atom other than carbon in 1 or 2 locations in a hydrocarbon group).

To provide a sanitary facility member having excellent ease of contamination removal and excellent persistence of ease of contamination removal. A sanitary facility member including: a base material, at least the surface of which includes a metal element; a metal oxide layer formed on the surface of the base material; and an organic layer provided on the metal oxide layer; wherein the metal element is at least one element selected from the group consisting of Cr, Zr, and Ti, the metal oxide layer includes at least the metal element and an oxygen element, and the organic layer is bonded to the metal oxide layer by bonding (M-O—P bonding) of the metal element (M) and a phosphorus atom (P) of at least one group (X) selected from a phosphonic acid group, a phosphoric acid group, and a phosphinic acid group via an oxygen atom (O), the group X being bonded to a group R (where R is a hydrocarbon or a group having an atom other than carbon in 1 or 2 locations in a hydrocarbon group).

A production method for a treatment solution for forming an insulating coating. The method includes mixing a solution A containing, on a PO.sub.4.sup.3− basis, 0.20 mol/L or more and 10 mol/L or less of at least one of (i) phosphoric acid and (ii) a phosphate salt, and containing, on a metal basis, less than 0.50 mol/L of one or more particulate metal compounds, and a solution B containing, on a metal basis, 0.50 mol/L or more and 20.0 mol/L or less of the one or more particulate metal compounds, and containing, on a PO.sub.4.sup.3− basis, less than 0.20 mol/L of at least one of (i) phosphoric acid and (ii) a phosphate salt, and stirring with a turbine stator-type high-speed stirrer such that a peripheral speed of a turbine reaches 10 m/s or more within 60 seconds after starting the mixing of the solution A and the solution B.

Described are metal bodies made of magnesium-containing metal and having a magnesium fluoride surface passivation region formed at a surface of the body, as well as methods of forming a magnesium fluoride surface passivation region at a surface of a metal body, and uses for the bodies.