Disclosed is a combined treatment method for improving corrosion resistance of metal component in chlorine-containing solution. First, the metal component is placed in the chlorine-containing solution. Large-area overlapping laser shock peening without an absorbing layer is used, when laser pulses are irradiated on the target metal component, the metal matrix surface absorbs the laser energy, vaporizes and expands to form a high-temperature and high-pressure plasma, a chlorine-containing passivation film is formed, to improve the surface corrosion resistance of the metal component. After that, the surface layer of the metal component is subjected to surface polishing, followed by large-area overlapping laser shock peening with an absorbing layer at room temperature, to further improve the corrosion resistance of the metal component. The combined treatment method of the present invention can be applied to improve the corrosion resistance of metal components in highly corrosive chlorine-containing environments of seawater and the like.

Disclosed is a combined treatment method for improving corrosion resistance of metal component in chlorine-containing solution. First, the metal component is placed in the chlorine-containing solution. Large-area overlapping laser shock peening without an absorbing layer is used, when laser pulses are irradiated on the target metal component, the metal matrix surface absorbs the laser energy, vaporizes and expands to form a high-temperature and high-pressure plasma, a chlorine-containing passivation film is formed, to improve the surface corrosion resistance of the metal component. After that, the surface layer of the metal component is subjected to surface polishing, followed by large-area overlapping laser shock peening with an absorbing layer at room temperature, to further improve the corrosion resistance of the metal component. The combined treatment method of the present invention can be applied to improve the corrosion resistance of metal components in highly corrosive chlorine-containing environments of seawater and the like.

Provided are an austenitic heat resistant alloy capable of exhibiting sufficient molten-salt corrosion resistance even when exposed to a molten salt of 600° C. and a production method thereof, and an austenitic heat-resistant alloy material. An austenitic heat resistant alloy includes a base metal, and a Ni—Fe oxide having a spinel structure on or above the surface of the base metal. The base metal has a chemical composition consisting of, in mass %, C: 0.030 to 0.120%, Si: 0.02 to 1.00%, Mn: 0.10 to 2.00%, Cr: 20.0% or more to less than 28.0%, Ni: more than 35.0% to 50.0% or less, W: 4.0 to 10.0%, Ti: 0.01 to 0.30%, Nb: 0.01 to 1.00%, sol. Al: 0.0005 to 0.0400%, B: 0.0005 to 0.0100%, Mo: less than 0.5%, Co: 0 to 0.80%, and Cu: 0 to 0.50%, with the balance being Fe and impurities.

Provided are an austenitic heat resistant alloy capable of exhibiting sufficient molten-salt corrosion resistance even when exposed to a molten salt of 600° C. and a production method thereof, and an austenitic heat-resistant alloy material. An austenitic heat resistant alloy includes a base metal, and a Ni—Fe oxide having a spinel structure on or above the surface of the base metal. The base metal has a chemical composition consisting of, in mass %, C: 0.030 to 0.120%, Si: 0.02 to 1.00%, Mn: 0.10 to 2.00%, Cr: 20.0% or more to less than 28.0%, Ni: more than 35.0% to 50.0% or less, W: 4.0 to 10.0%, Ti: 0.01 to 0.30%, Nb: 0.01 to 1.00%, sol. Al: 0.0005 to 0.0400%, B: 0.0005 to 0.0100%, Mo: less than 0.5%, Co: 0 to 0.80%, and Cu: 0 to 0.50%, with the balance being Fe and impurities.

There is provided a method for manufacturing a galvanized steel sheet that has low sliding resistance in press forming and good degreasing property even under severe alkaline degreasing treatment conditions due to low temperature and short process line length. An oxide layer formed on the surface of a galvanized steel sheet is subjected to neutralization treatment using an alkaline aqueous solution containing 0.01 g/L or more of P ions and 0.01 g/L or more of colloid dispersed particles, wherein the alkaline aqueous solution preferably contains at least one phosphorus compound selected from phosphates, pyrophosphates, and triphosphates and at least one type of colloid dispersed particles selected from Ti, silica, Pt, Pd, Zr, Ag, Cu, Au, and Mg.

There is provided a method for manufacturing a galvanized steel sheet that has low sliding resistance in press forming and good degreasing property even under severe alkaline degreasing treatment conditions due to low temperature and short process line length. An oxide layer formed on the surface of a galvanized steel sheet is subjected to neutralization treatment using an alkaline aqueous solution containing 0.01 g/L or more of P ions and 0.01 g/L or more of colloid dispersed particles, wherein the alkaline aqueous solution preferably contains at least one phosphorus compound selected from phosphates, pyrophosphates, and triphosphates and at least one type of colloid dispersed particles selected from Ti, silica, Pt, Pd, Zr, Ag, Cu, Au, and Mg.

A method of producing a hot-dip Zn alloy-plated steel sheet includes: dipping a base steel sheet in a hot-dip Zn alloy plating bath to form a hot-dip Zn alloy plating layer on a surface of the base steel sheet; and contacting an aqueous solution containing a water-soluble corrosion inhibitor with a surface of the hot-dip Zn alloy plating layer to cool the base steel sheet and the hot-dip Zn alloy plating layer having a raised temperature through formation of the hot-dip Zn alloy plating layer. A temperature of the surface of the hot-dip Zn alloy plating layer when the aqueous solution is to be contacted with the surface of the hot-dip Zn alloy plating layer is equal to or more than 100° C. and equal to or less than a solidifying point of the plating layer. The aqueous solution containing the water-soluble corrosion inhibitor satisfies the Equation [{(Z.sub.0−Z.sub.1)/Z.sub.0}100≧201.

A method for continuously annealing aluminium alloy sheet at final thickness by continuously moving heat-treatable AlMgSi aluminium alloy sheet through a continuous annealing furnace arranged to heat the moving aluminium sheet to a set soaking temperature (T.sub.SET) in the temperature range of 500° C. to 590° C., the continuous annealing furnace has an entry section and an exit section, the moving aluminium sheet moves substantially horizontally through the continuous annealing furnace, wherein the moving aluminium sheet is rapidly cooled on leaving the exit section, wherein before or near the entry section of the continuous annealing furnace the moving aluminium sheet is pre-heated to a temperature of 5° C. to 100° C. below the T.sub.SET using an average heat-up rate as function of sheet thickness of at least Y=−31.Math.ln(X)+50, wherein Y is the heat-up rate in ° C./sec and X is the sheet thickness in mm.

A method for continuously annealing aluminium alloy sheet at final thickness by continuously moving heat-treatable AlMgSi aluminium alloy sheet through a continuous annealing furnace arranged to heat the moving aluminium sheet to a set soaking temperature (T.sub.SET) in the temperature range of 500° C. to 590° C., the continuous annealing furnace has an entry section and an exit section, the moving aluminium sheet moves substantially horizontally through the continuous annealing furnace, wherein the moving aluminium sheet is rapidly cooled on leaving the exit section, wherein before or near the entry section of the continuous annealing furnace the moving aluminium sheet is pre-heated to a temperature of 5° C. to 100° C. below the T.sub.SET using an average heat-up rate as function of sheet thickness of at least Y=−31.Math.ln(X)+50, wherein Y is the heat-up rate in ° C./sec and X is the sheet thickness in mm.

An object of the invention is to provide a fishhook for fishing or the like, the fishhook being easily stuck to a fish or the like and being also excellent in durability. The surface of a fishhook is treated with a compound selected from the group consisting of a metallic surfactant having at least one or more hydroxyl groups or hydrolyzable groups, a fluorine-based surface treating agent, a thiol compound and a disulfide compound.