A surface treatment solution composition for forming an inorganic film, comprising: 10 to 30% by weight of a trivalent chromium compound containing chromium phosphate (A) and chromium nitrate (B) and satisfying a content ratio A/(A+B) of 0.3 to 0.6; 5 to 50% by weight of a silane compound; 0.2 to 3% by weight of a vanadium-based rust-inhibiting and corrosion-resisting agent; 0.5 to 5% by weight of a cobalt-based rust-inhibiting and corrosion-resisting agent; and 12 to 84.3% by weight of water, an alloyed hot-dip galvanized steel sheet surface-treated using the composition, and a method for manufacturing the alloyed hot-dip galvanized steel sheet, are provided, and the surface treatment solution composition containing the trivalent chromium compound has an excellent effect on corrosion resistance, blackening resistance, fuel resistance, weldability, and alkali resistance.

A surface treatment solution composition for forming an inorganic film, comprising: 10 to 30% by weight of a trivalent chromium compound containing chromium phosphate (A) and chromium nitrate (B) and satisfying a content ratio A/(A+B) of 0.3 to 0.6; 5 to 50% by weight of a silane compound; 0.2 to 3% by weight of a vanadium-based rust-inhibiting and corrosion-resisting agent; 0.5 to 5% by weight of a cobalt-based rust-inhibiting and corrosion-resisting agent; and 12 to 84.3% by weight of water, an alloyed hot-dip galvanized steel sheet surface-treated using the composition, and a method for manufacturing the alloyed hot-dip galvanized steel sheet, are provided, and the surface treatment solution composition containing the trivalent chromium compound has an excellent effect on corrosion resistance, blackening resistance, fuel resistance, weldability, and alkali resistance.

The present invention relates to a solution that is free of chromium in all its oxidising states, comprising: - at least one chemical oxidising compound, - at least one aluminium complexing agent, - at least one corrosion inhibiting compound, and -optionally, a chemical sealant compound, the solution having a pH in the range from 1 to 5. The present invention also relates to a method for treating a metal surface, comprising the application, on the surface, of a solution as defined above. The present invention additionally relates to a coating of a metal surface that can be obtained by the method for treating a metal surface as defined above, to a metal surface comprising the coating and to the use of the solution in an anti-corrosion treatment of a metal surface.

The present invention relates to a solution that is free of chromium in all its oxidising states, comprising: - at least one chemical oxidising compound, - at least one aluminium complexing agent, - at least one corrosion inhibiting compound, and -optionally, a chemical sealant compound, the solution having a pH in the range from 1 to 5. The present invention also relates to a method for treating a metal surface, comprising the application, on the surface, of a solution as defined above. The present invention additionally relates to a coating of a metal surface that can be obtained by the method for treating a metal surface as defined above, to a metal surface comprising the coating and to the use of the solution in an anti-corrosion treatment of a metal surface.

A trivalent-chromium chemical conversion coating from which substantially no hexavalent chromium is released. The trivalent-chromium chemical conversion coating is one formed on the surface of a zinc or zinc-alloy deposit. In a brine spray test, the chemical conversion coating has unsusceptibility to corrosion (time required for white-rust formation) of 96 hours or longer. The chemical conversion coating has a hexavalent-chromium concentration less than 0.01 μg/cm.sup.2 in terms of metal atom amount. The amount of hexavalent chromium released after 30-day standing in a thermo-hygrostatic chamber at a temperature of 80° C. and a humidity of 95% (amount of hexavalent chromium released when the coating is immersed in 100° C. water for 10 minutes) is smaller than 0.05 μg/cm.sup.2.

An insulating coating for an electrical steel sheet is provided that is formed on a surface of a base metal of the electrical steel sheet and that contains a polyvalent metal phosphate of one or more elements selected from Al, Zn, Mg and Ca, and has an enriched layer of a divalent metal at an interface with the surface of the base metal. An enrichment of the divalent metal contained in the enriched layer is 0.01 g/m.sup.2 or more and less than 0.2 g/m.sup.2.

An insulating coating for an electrical steel sheet is provided that is formed on a surface of a base metal of the electrical steel sheet and that contains a polyvalent metal phosphate of one or more elements selected from Al, Zn, Mg and Ca, and has an enriched layer of a divalent metal at an interface with the surface of the base metal. An enrichment of the divalent metal contained in the enriched layer is 0.01 g/m.sup.2 or more and less than 0.2 g/m.sup.2.

A trivalent-chromium chemical conversion coating from which substantially no hexavalent chromium is released. The trivalent-chromium chemical conversion coating is one formed on the surface of a zinc or zinc-alloy deposit. In a brine spray test, the chemical conversion coating has unsusceptibility to corrosion (time required for white-rust formation) of 96 hours or longer. The chemical conversion coating has a hexavalent-chromium concentration less than 0.01 μg/cm.sup.2 in terms of metal atom amount. The amount of hexavalent chromium released after 30-day standing in a thermo-hygrostatic chamber at a temperature of 80° C. and a humidity of 95% (amount of hexavalent chromium released when the coating is immersed in 100° C. water for 10 minutes) is smaller than 0.05 μg/cm.sup.2.

A trivalent-chromium chemical conversion coating from which substantially no hexavalent chromium is released. The trivalent-chromium chemical conversion coating is one formed on the surface of a zinc or zinc-alloy deposit. In a brine spray test, the chemical conversion coating has unsusceptibility to corrosion (time required for white-rust formation) of 96 hours or longer. The chemical conversion coating has a hexavalent-chromium concentration less than 0.01 μg/cm.sup.2 in terms of metal atom amount. The amount of hexavalent chromium released after 30-day standing in a thermo-hygrostatic chamber at a temperature of 80° C. and a humidity of 95% (amount of hexavalent chromium released when the coating is immersed in 100° C. water for 10 minutes) is smaller than 0.05 μg/cm.sup.2.

A surface treatment solution composition for forming an inorganic film, comprising: 10 to 30% by weight of a trivalent chromium compound containing chromium phosphate (A) and chromium nitrate (B) and satisfying a content ratio A/(A+B) of 0.3 to 0.6; 5 to 50% by weight of a silane compound; 0.2 to 3% by weight of a vanadium-based rust-inhibiting and corrosion-resisting agent; 0.5 to 5% by weight of a cobalt-based rust-inhibiting and corrosion-resisting agent; and 12 to 84.3% by weight of water, an alloyed hot-dip galvanized steel sheet surface-treated using the composition, and a method for manufacturing the alloyed hot-dip galvanized steel sheet, are provided, and the surface treatment solution composition containing the trivalent chromium compound has an excellent effect on corrosion resistance, blackening resistance, fuel resistance, weldability, and alkali resistance.