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.

The present invention provides a chemical conversion liquid for zinc or zinc alloy bases, which contains 2-200 mmol/L of trivalent chromium ions, 1-300 mmol/L of zirconium ions and at least one component selected from among fluorine ions, a water-soluble carboxylic acid and a salt thereof, and which does not contain Co ions and hexavalent chromium ions.

The present invention provides a chemical conversion liquid for zinc or zinc alloy bases, which contains 2-200 mmol/L of trivalent chromium ions, 1-300 mmol/L of zirconium ions and at least one component selected from among fluorine ions, a water-soluble carboxylic acid and a salt thereof, and which does not contain Co ions and hexavalent chromium ions.

Provided are a treatment liquid for a black trivalent chromium conversion coating, and a trivalent chromium-containing water-soluble liquid for finishing treatment, 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. The treatment liquid for a black trivalent chromium conversion coating on the surface of a metal substrate contains a trivalent chromium compound, two or more organic acids or organic acid salts, or one or more organic sulfur compounds, and nitrate ions, and contains no cobalt compound.

Provided are a treatment liquid for a black trivalent chromium conversion coating, and a trivalent chromium-containing water-soluble liquid for finishing treatment, 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. The treatment liquid for a black trivalent chromium conversion coating on the surface of a metal substrate contains a trivalent chromium compound, two or more organic acids or organic acid salts, or one or more organic sulfur compounds, and nitrate ions, and contains no cobalt compound.

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.

Provided is a zinc-based plated steel sheet having a post-treated coating filmed thereon including: a steel sheet; a zinc plated layer formed on the steel sheet; and a post-treated coating formed on the plated layer, wherein the atomic ratio (O/M) of oxygen (O) to metals (M) contained in the post-treated coating is greater than 2 and less than 20, and a method for post-treating a zinc-based plated steel sheet. According to this, the zinc-based plated steel sheet having the post-treated coating formed thereon has the effects excellent in lubricity, weldability, adhesiveness, film-removing property and paintability. As the method of post-treating a zinc-based plated steel sheet of the present invention employs a simple coating method irrespective of the kind of plating layer, the process is simple and economical and the process operation cost is low.

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 method for producing a chemically treated alloy material is provided that suppresses a decrease in chemical treatability even in a case where chemical treatment is repeatedly performed. The method for producing a chemically treated alloy material of the present disclosure includes a chemical treatment step and a treatment solution regeneration step. In the chemical treatment step, an alloy material (6) is immersed in an oxalate treatment solution (4) containing oxalate ions and fluorine ions to perform a chemical treatment. In the treatment solution regeneration step, light is radiated to the oxalate treatment solution (4) during the chemical treatment and/or the oxalate treatment solution (4) after the chemical treatment.