A structural member may include a primary metal member having a metal surface containing iron, the metal surface susceptible to corrosion, and a protective outer coating formed on the metal surface to resist corrosion. The coating may include a polyaspartic top coat layer and a passivation layer. The coating may be formed of a first part including an inorganic acid phosphate mixture and a second part including an inorganic alkaline metal oxide or hydroxide mixture. The first part may include an inorganic acid phosphate mixture having acidic phosphate component, filler, water as solvent, suspension agent, and nonionic surfactant. The second part may include an inorganic alkaline metal oxide or hydroxide mixture having metal oxide or hydroxide, filler, water as solvent, suspension agent, and surfactant.

A structural member may include a primary metal member having a metal surface containing iron, the metal surface susceptible to corrosion, and a protective outer coating formed on the metal surface to resist corrosion. The coating may include a polyaspartic top coat layer and a passivation layer. The coating may be formed of a first part including an inorganic acid phosphate mixture and a second part including an inorganic alkaline metal oxide or hydroxide mixture. The first part may include an inorganic acid phosphate mixture having acidic phosphate component, filler, water as solvent, suspension agent, and nonionic surfactant. The second part may include an inorganic alkaline metal oxide or hydroxide mixture having metal oxide or hydroxide, filler, water as solvent, suspension agent, and surfactant.

A grain-oriented magnetic steel sheet with chromium-free insulating tension coating includes a grain-oriented magnetic steel sheet and an insulating tension coating containing a phosphate salt and silica on a surface of the grain-oriented magnetic steel sheet, the coating further including a crystalline compound represented by the general formula (1): M.sup.II.sub.3M.sup.III.sub.4(X.sup.VO.sub.4).sub.6 . . . (1). A method for producing a grain-oriented magnetic steel sheet with chromium-free insulating tension coating includes applying an insulating tension coating liquid to a surface of a finish annealed grain-oriented magnetic steel sheet, the coating liquid including colloidal silica, a phosphate salt and a metal element M-containing compound in a specific ratio, and heat treating the steel sheet at least one time at a temperature of not less than 900° C. in an atmosphere including a non-oxidizing gas and having a dew point of not more than 0° C.

A grain-oriented magnetic steel sheet with chromium-free insulating tension coating includes a grain-oriented magnetic steel sheet and an insulating tension coating containing a phosphate salt and silica on a surface of the grain-oriented magnetic steel sheet, the coating further including a crystalline compound represented by the general formula (1): M.sup.II.sub.3M.sup.III.sub.4(X.sup.VO.sub.4).sub.6 . . . (1). A method for producing a grain-oriented magnetic steel sheet with chromium-free insulating tension coating includes applying an insulating tension coating liquid to a surface of a finish annealed grain-oriented magnetic steel sheet, the coating liquid including colloidal silica, a phosphate salt and a metal element M-containing compound in a specific ratio, and heat treating the steel sheet at least one time at a temperature of not less than 900° C. in an atmosphere including a non-oxidizing gas and having a dew point of not more than 0° C.

A grain-oriented electrical steel sheet according to the present invention includes a silicon steel sheet as a base steel sheet, and when an average value of amplitudes in a wavelength range of 20 to 100 μm among wavelength components obtained by performing Fourier analysis on a measured cross-sectional curve parallel to a sheet width direction of the silicon steel sheet is set as ave-AMP.sub.C100, ave-AMP.sub.C100 is 0.0001 to 0.050 μm.

A solution for forming an insulation coating of grain-oriented electrical steel sheet includes an aqueous solution prepared by mixing a phosphate solution and colloidal silica. Chromium is not added to the aqueous solution. The colloidal silica includes silica particles surface-modified by an aluminate or is prepared by adding an aluminate to colloidal silica such as conventional colloidal silica.

A solution for forming an insulation coating of grain-oriented electrical steel sheet includes an aqueous solution prepared by mixing a phosphate solution and colloidal silica. Chromium is not added to the aqueous solution. The colloidal silica includes silica particles surface-modified by an aluminate or is prepared by adding an aluminate to colloidal silica such as conventional colloidal silica.

A method for phosphating metal surfaces in a layer-forming manner using a colloidal aqueous solution as an activation stage containing a dispersed particulate constituent, the particulate constituent containing dispersed inorganic compounds of phosphates of polyvalent metal cations; plus polymeric organic compounds as dispersing agents, which are composed at least partially of styrene and/or an α-olefin having no more than 5 carbon atoms and are composed at least partially of maleic acid, its anhydride and/or its imide, the polymeric organic compounds additionally comprising polyoxyalkylene units. In the activation stage of the method according to the invention, the addition of condensed phosphates can be dispensed with such that the content of dissolved condensed phosphates in the colloidal aqueous solution is less than 0.25, based on the phosphate content in the particulate constituent thereof, in each case based on the element P.

A method for phosphating metal surfaces in a layer-forming manner using a colloidal aqueous solution as an activation stage containing a dispersed particulate constituent, the particulate constituent containing dispersed inorganic compounds of phosphates of polyvalent metal cations; plus polymeric organic compounds as dispersing agents, which are composed at least partially of styrene and/or an α-olefin having no more than 5 carbon atoms and are composed at least partially of maleic acid, its anhydride and/or its imide, the polymeric organic compounds additionally comprising polyoxyalkylene units. In the activation stage of the method according to the invention, the addition of condensed phosphates can be dispensed with such that the content of dissolved condensed phosphates in the colloidal aqueous solution is less than 0.25, based on the phosphate content in the particulate constituent thereof, in each case based on the element P.

Provided is a non-oriented electrical steel sheet having excellent adhesion with an insulating coating even if the thickness of the insulating coating is reduced. The non-oriented electrical steel sheet of the present disclosure has an insulating coating on at least one surface of the steel sheet, where the insulating coating has a P-concentrated layer on both a surface side and an interface side with a steel substrate, and a P concentration of the P-concentrated layer is higher than a P concentration in the steel substrate.