A high-strength galvanized steel sheet is excellent in the external appearance of plating and the hydrogen brittleness resistance, and has a high yield ratio, and a method for manufacturing the same. The high-strength galvanized steel sheet including a steel sheet having a specific component composition and a specific steel structure, the amount of diffusible hydrogen in the steel sheet being 0.20 mass ppm or less; and a galvanizing layer provided on a surface of the steel sheet, the galvanizing layer having a content amount of Fe of 8 to 15% in mass %, and an attachment amount of plating per one surface of 20 to 120 g/m.sup.2, wherein the amount of Mn oxides contained in the galvanizing layer is 0.050 g/m.sup.2 or less; and the high-strength galvanized steel sheet has a yield strength of 700 MPa or more and a yield strength ratio of 65% or more and less than 85%.

A high-strength galvanized steel sheet is excellent in the external appearance of plating and the hydrogen brittleness resistance, and has a high yield ratio, and a method for manufacturing the same. The high-strength galvanized steel sheet including a steel sheet having a specific component composition and a specific steel structure, the amount of diffusible hydrogen in the steel sheet being 0.20 mass ppm or less; and a galvanizing layer provided on a surface of the steel sheet, the galvanizing layer having a content amount of Fe of 8 to 15% in mass %, and an attachment amount of plating per one surface of 20 to 120 g/m.sup.2, wherein the amount of Mn oxides contained in the galvanizing layer is 0.050 g/m.sup.2 or less; and the high-strength galvanized steel sheet has a yield strength of 700 MPa or more and a yield strength ratio of 65% or more and less than 85%.

A method is used for cleaning heat exchanger systems. The method is performed at a computer system having one or more processors and memory storing one or more programs configured for execution by the one or more processors. The method determines component percentages of a cleaning solution based, at least in part, on operational parameters of a heat exchanger system. The operational parameters include chemical composition of fluids passing through the heat exchanger system and operating temperatures of the fluids passing through the heat exchanger system. The component percentages of the cleaning solution include: (1) hydrogen peroxide, 2-90 wt. %; (2) a complexing agent, 3-30 wt. %; (3) water-soluble calixarene, 0.01-10 wt. %; and (4) water. The complexing agent includes a polybasic organic acid or a sodium salt thereof, or a derivative of phosphorous acid.

Disclosed is a high-strength steel sheet having a tensile strength (TS) of 780 MPa or more and excellent in ductility, fatigue properties, stretch flangeability, surface characteristics, and sheet passage ability that can be obtained by providing a predetermined chemical composition and a steel microstructure that contains, by area, 20-50% of ferrite, 5-25% of bainitic ferrite, 1-10% of martensite, and 5-15% of tempered martensite, and that contains, by volume, 10% or more of retained austenite, in which the retained austenite has a mean grain size of 2 μm or less, a mean Mn content in the retained austenite in mass % is at least 1.2 times the Mn content in the steel sheet in mass %, the retained austenite has a mean free path of 1.2 μm or less, and the tempered martensite has a mean free path of 1.2 μm or less.

Disclosed is a high-strength steel sheet having a tensile strength (TS) of 780 MPa or more and excellent in ductility, fatigue properties, stretch flangeability, surface characteristics, and sheet passage ability that can be obtained by providing a predetermined chemical composition and a steel microstructure that contains, by area, 20-50% of ferrite, 5-25% of bainitic ferrite, 1-10% of martensite, and 5-15% of tempered martensite, and that contains, by volume, 10% or more of retained austenite, in which the retained austenite has a mean grain size of 2 μm or less, a mean Mn content in the retained austenite in mass % is at least 1.2 times the Mn content in the steel sheet in mass %, the retained austenite has a mean free path of 1.2 μm or less, and the tempered martensite has a mean free path of 1.2 μm or less.

Disclosed is a method comprising: preparing a steel slab with a predetermined chemical composition; subjecting the steel slab to hot rolling by heating it to a temperature of 1100-1300° C., hot rolling it with a finisher delivery temperature of 800-1000° C. to form a hot-rolled steel sheet, and coiling the steel sheet at a mean coiling temperature of 200-500° C.; subjecting the steel sheet to pickling treatment; and subjecting the steel sheet to annealing by retaining the steel sheet at a temperature of 740-840° C. for 10-900 s, then cooling the steel sheet at a mean cooling rate of 5-50° C./s to a cooling stop temperature of higher than 350° C. and 550° C. or lower, and retaining the steel sheet in a temperature range of higher than 350° C. to 550° C. for 10 s or more.

Disclosed is a method comprising: preparing a steel slab with a predetermined chemical composition; subjecting the steel slab to hot rolling by heating it to a temperature of 1100-1300° C., hot rolling it with a finisher delivery temperature of 800-1000° C. to form a hot-rolled steel sheet, and coiling the steel sheet at a mean coiling temperature of 200-500° C.; subjecting the steel sheet to pickling treatment; and subjecting the steel sheet to annealing by retaining the steel sheet at a temperature of 740-840° C. for 10-900 s, then cooling the steel sheet at a mean cooling rate of 5-50° C./s to a cooling stop temperature of higher than 350° C. and 550° C. or lower, and retaining the steel sheet in a temperature range of higher than 350° C. to 550° C. for 10 s or more.

A method for manufacturing a high-strength galvanized steel sheet having excellent strength-elongation balance, coating adhesiveness, and surface appearance. The method includes: (i) a first heating process of heating a steel sheet having a predetermined chemical composition, (ii) a first pickling process of pickling the steel sheet which was subjected to the first heating process in an oxidizing acidic aqueous solution, (iii) a second pickling process of pickling the steel sheet which was subjected to the first pickling process in a non-oxidizing acidic aqueous solution, (iv) a second heating process of holding the steel sheet, which was subjected to the second pickling process, at a temperature range of 700° C. or higher and 900° C. or lower in a hydrogen-containing atmosphere for 20 seconds or more and 300 seconds or less, and (v) performing a galvanizing treatment on the steel sheet which was subjected to the second heating process.

A method of forming a cured film on an aluminum substrate includes depositing a film formed from a sol-gel coating composition onto the aluminum substrate without disposing a conversion coating composition onto the aluminum substrate. The method also includes, after depositing, curing the film. A coating system includes an aluminum substrate having a surface and a cured film disposed on and in contact with the surface. The cured film is formed from a sol-gel coating composition. The coating system is free from a layer formed from a conversion coating composition.

Methods and compositions are disclosed for inhibiting corrosion on metal surfaces of gas turbine air compressors. The methods comprise contacting the metal surfaces with a corrosion inhibiting composition comprising at least one filming amine.