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 coating agent for forming a grain-oriented electrical steel sheet coating able to form an aluminum borate coating high in adhesion and large in tension and a method for manufacturing the grain-oriented electrical steel sheet are provided. The coating agent for forming a grain-oriented electrical steel sheet coating of the present invention comprises an aluminum source containing aluminum oxide and/or an aluminum oxide precursor compound, a boron source containing a borate of an alkali metal, and silicon oxide and/or a silicon oxide precursor in an amount, converted to silicon oxide, of 5 mass % or more and 10 mass % or less with respect to a total solids concentration of the aluminum source and boron source, the aluminum source and the boron source contained so that, by molar ratio, Al/B: 0.5 to 2.0, a solids concentration of a total of the aluminum source and the boron source being 20 mass % or more and 38 mass % or less, and pH being 2.0 or more and 6.0 or less.

A coating agent for forming a grain-oriented electrical steel sheet coating able to form an aluminum borate coating high in adhesion and large in tension and a method for manufacturing the grain-oriented electrical steel sheet are provided. The coating agent for forming a grain-oriented electrical steel sheet coating of the present invention comprises an aluminum source containing aluminum oxide and/or an aluminum oxide precursor compound, a boron source containing a borate of an alkali metal, and silicon oxide and/or a silicon oxide precursor in an amount, converted to silicon oxide, of 5 mass % or more and 10 mass % or less with respect to a total solids concentration of the aluminum source and boron source, the aluminum source and the boron source contained so that, by molar ratio, Al/B: 0.5 to 2.0, a solids concentration of a total of the aluminum source and the boron source being 20 mass % or more and 38 mass % or less, and pH being 2.0 or more and 6.0 or less.

Described herein is a simplified process for a pretreatment of metallic substrates for cold forming. Also described herein are a corresponding reactive lubricant, a metallic substrate which has been pretreated by the process, and a method of using the pretreated metallic substrate.

The invention relates to a method for producing a silane-modified silicate. In order to obtain optimal corrosion protection properties, a silane compound according to the invention is at least partially hydrolyzed and/or condensed in the presence of a silicate compound at a pH value greater than or equal to 8 and then a pH value less than or equal to 7 is set by adding acid. The invention further relates to an aqueous acidic passivation composition for metal substrate coated with the passivation composition.

The invention relates to a method for producing a silane-modified silicate. In order to obtain optimal corrosion protection properties, a silane compound according to the invention is at least partially hydrolyzed and/or condensed in the presence of a silicate compound at a pH value greater than or equal to 8 and then a pH value less than or equal to 7 is set by adding acid. The invention further relates to an aqueous acidic passivation composition for metal substrate coated with the passivation composition.

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.

Process for treating metal such as aluminum and its alloys to prevent corrosion which comprises coating the metal with a chromium-free conversion composition containing effective amounts of metal fluorozirconates and carboxylic metal salts.

A method for producing a heat exchanger having at least one cooling line with a lightweight metal base through which a water-based coolant can flow may include passivating a surface of the at least one cooling line, which is in contact with the coolant, before the at least one cooling line is filled with the coolant.