This invention relates to an aqueous solution and a method for preparing an organic protective coating on a Cr(lll) conversion layer which is localized on (anodized) aluminium (alloy) to enhance corrosion protection. The composition is an aqueous solution which contains water, an organic film forming agent and a corrosion inhibitor, wherein the corrosion inhibitor comprises or consists of at least one 2-arylriazole. According to the method of the present invention, the composition is used for post-treating of a Cr(lll) conversion layer on (anodized) aluminium (alloy). The invention further provides a modified Cr(III) conversion coating on (anodized) aluminium (alloy), which is producible or produced with the inventive method. The modified Cr(III) conversion coating according to the invention shows excellent corrosion protection, paint adhesion and electrical resistivity.

An aqueous conversion coating solution comprises a trivalent chromium compound, a zirconate compound, and a dye compound. The trivalent chromium compound can comprise trivalent chromium compounds such as trivalent chromium sulfate. The dye compound can comprise an azo dye, a chromium complex dye, an anthraquinoid dye, and/or a methine dye. The zirconate compound can comprise alkali metal hexafluorozirconate compounds. The conversion coating solution can comprise a phosphorous compound such as an organic amino-phosphonic acid compound. The conversion coating solution can be formed by mixing a dye additive containing the dye with a trivalent chromium conversion coating solution that does not contain a dye. The conversion coating solution can be used to treat metal substrates comprising aluminum, magnesium, and/or zinc.

An apparatus for the implementation of a process for the continuous manufacturing of steel strips for packaging coated with a passivation layer is provided. An apparatus contains a transfer roller; a coating roller contacting the transfer roller, a surface of the coating roller having a plurality of hexagonally shaped cells with a line count being from 50 to 200 lines per centimeter and a volume being from 5.Math.10.sup.?6 to 10.Math.10.sup.?6 m.sup.3 per square meter of the coating roller surface; and a tank containing an aqueous passivation solution, the tank providing the aqueous passivation solution to the coating roller.

An apparatus for the implementation of a process for the continuous manufacturing of steel strips for packaging coated with a passivation layer is provided. An apparatus contains a transfer roller; a coating roller contacting the transfer roller, a surface of the coating roller having a plurality of hexagonally shaped cells with a line count being from 50 to 200 lines per centimeter and a volume being from 5.Math.10.sup.?6 to 10.Math.10.sup.?6 m.sup.3 per square meter of the coating roller surface; and a tank containing an aqueous passivation solution, the tank providing the aqueous passivation solution to the coating roller.

The present invention relates to a method for adjusting a passivation composition by determining the redox potential of a passivation composition as well as to a method for passivating metallic substrates by treatment with a passivation composition.

An object is to provide a trivalent chromium chemical conversion treatment liquid for a zinc or zinc alloy base capable of forming an environmentally-friendly chemical conversion coating with high corrosion resistance. The present invention provides a hexavalent chromium-free trivalent chromium chemical conversion treatment liquid for zinc or zinc alloy, the liquid comprising trivalent chromium ions, zirconium ions, nitrate ions, and chain colloidal silica, in which the pH of the treatment liquid is 2.5 to 5.0.

A process for continuous manufacturing of steel strips for packaging coated with a passivation layer is provided. The layer is an aqueous passivation solution, the thickness of which is less than 3 ?m and the viscosity of which is less than 1.5.Math.10.sup.?3 Pa.Math.s at 20? C., and is deposited on one of the faces of the strip. This depositing is carried out by a transfer roller in contact with the strip and with a second coating roller, the surface of which has a plurality of hexagonally shaped cells, the line count of which is between 50 and 200 lines per centimeter, and the total volume of which is between 5.Math.10.sup.?6 and 10.Math.10.sup.?6 m.sup.3 per square meter of roller surface. The coating roller is fed with aqueous passivation solution by dipping in a tank equipped with wiping means and the strip runs at a speed greater than or equal to 400 m/m. An apparatus for implementation of the process is also provided.

A process for continuous manufacturing of steel strips for packaging coated with a passivation layer is provided. The layer is an aqueous passivation solution, the thickness of which is less than 3 ?m and the viscosity of which is less than 1.5.Math.10.sup.?3 Pa.Math.s at 20? C., and is deposited on one of the faces of the strip. This depositing is carried out by a transfer roller in contact with the strip and with a second coating roller, the surface of which has a plurality of hexagonally shaped cells, the line count of which is between 50 and 200 lines per centimeter, and the total volume of which is between 5.Math.10.sup.?6 and 10.Math.10.sup.?6 m.sup.3 per square meter of roller surface. The coating roller is fed with aqueous passivation solution by dipping in a tank equipped with wiping means and the strip runs at a speed greater than or equal to 400 m/m. An apparatus for implementation of the process is also provided.

A hearth roll for heat treatment furnaces has excellent build-up resistance, has a hexavalent-chromium-free thermal spray coating film formed on the roll surface thereof and is safe for the environment. A method for manufacturing a hearth roll for continuous annealing furnaces includes a first step of applying an aqueous solution containing chromium phosphate onto a thermal spray coating film formed on the roll surface of a hearth roll or impregnating the thermal spray coating film with the aqueous solution; and a second step of burning the hearth roll.

A hearth roll for heat treatment furnaces has excellent build-up resistance, has a hexavalent-chromium-free thermal spray coating film formed on the roll surface thereof and is safe for the environment. A method for manufacturing a hearth roll for continuous annealing furnaces includes a first step of applying an aqueous solution containing chromium phosphate onto a thermal spray coating film formed on the roll surface of a hearth roll or impregnating the thermal spray coating film with the aqueous solution; and a second step of burning the hearth roll.