A method for making an environmentally-safe chromium based corrosion resistant coating includes pre-treating a metal substrate, immersing the metal substrate in a trivalent chromium bath which does not contain hexavalent chromium, post-treating the coated metal substrate with an oxidizer, and curing the coated metal substrate in a controlled environment.

Provided are a treatment liquid for a trivalent chromium conversion coating, achieving excellent corrosion resistance and scratch resistance without containing a cobalt compound, with high stability and adequate consideration for environmental issues; and a method for treating a metal substrate using the same. Provided is a treatment liquid for a trivalent chromium conversion coating on the surface of a metal substrate comprising: a trivalent chromium compound; titanium lactate; one or more compounds of transition metal other than cobalt; two or more organic acids or organic acid salts, and at least one ion species selected from chloride ions, nitrate ions, and sulfate ions; but no cobalt compound.

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 production method of a member having a surface provided thereon with a chemical conversion coating includes a contacting step and a washing step. The contacting step causes a reactive-type chemical conversion treating acidic composition to contact with a base material having a metal-based surface thereby forming a chemical conversion coating on the metal-based surface of the base material. The washing step washes the base material having been subjected to the contacting step to obtain a member having a surface provided thereon with the chemical conversion coating. The reactive-type chemical conversion treating acidic composition contains a water-soluble trivalent chromium-containing substance, a water-soluble titanium-containing substance, and a carboxylic acid compound. The acidic composition is free from a water-soluble cobalt-containing substance.

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 aqueous passivation composition, having a pH of less than 3, comprising: i) a source of trivalent chromium ions; ii) at least one -hydroxycarboxylic acid having general formula (I): R.sub.1CH(OH)COOH (I); wherein: R.sub.1 represents a hydrogen atom, a C1-C4 alkyl group, a C2-C6 alkenyl group, a C1-C6 alkoxy group, a C.sub.3-C.sub.6 cycloalkyl group or a C6-C10 aryl group; iii) phosphoric acid; iv) at least one water-soluble polyphosphonic acid or a water-soluble salt thereof, said polyphosphonic acid having general formula (II): Z[PO(OH).sub.2].sub.n (II); in which: n is at least 2; and Z is a connecting organic moiety having an effective valency of n, said polyphosphonic acid including at least two phosphonic groups separated by an alkylene bridge having 1 or 2 carbon atoms (C.sub.1-C.sub.2 alkylene); and v) at least one divalent metal cation;
wherein said composition is substantially free of: nitrate and fluoride anions, and hexavalent chromium.

Provided is a surface treatment solution composition comprising: 30 to 51 wt % of a trivalent chromium compound comprising chromium phosphate (A) and chromium nitrate (B) and having a content ratio of A/(A+B) that satisfies 0.3 to 0.6; 5 to 15 wt % of silane coupling agent; 0.2 to 3 wt % of vanadium-based anti-corrosive rust inhibitor; 3 to 12 wt % of colloidal silica; 0.5 to 5 wt % of polysiloxane copolymer; and 14 to 61.3 wt % of water, a hot dip galvanized steel sheet surface-treated using same, and a manufacturing method thereof. The hot dip galvanized steel sheet treated with the surface treatment solution composition containing trivalent chromium has an excellent corrosion resistance, blackening resistance, pipe-forming oil reactivity, and alkali resistance.

Provided is a surface treatment solution composition comprising: 30 to 51 wt % of a trivalent chromium compound comprising chromium phosphate (A) and chromium nitrate (B) and having a content ratio of A/(A+B) that satisfies 0.3 to 0.6; 5 to 15 wt % of silane coupling agent; 0.2 to 3 wt % of vanadium-based anti-corrosive rust inhibitor; 3 to 12 wt % of colloidal silica; 0.5 to 5 wt % of polysiloxane copolymer; and 14 to 61.3 wt % of water, a hot dip galvanized steel sheet surface-treated using same, and a manufacturing method thereof. The hot dip galvanized steel sheet treated with the surface treatment solution composition containing trivalent chromium has an excellent corrosion resistance, blackening resistance, pipe-forming oil reactivity, and alkali resistance.

A method (400) for applying a coating to a substrate (124) includes spraying (414) an aluminum-based coating layer (120) on the substrate. The coating layer is then infiltrated (420) with an aqueous solution (610). The solution comprises: a source of chromium; and potassium hexafluorozirconate.

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.