Provided herein is a method for specifically adjusting the electrical conductivity of a conversion coating, wherein a metallic surface or a conversion-coated metallic surface is treated with an aqueous composition which comprises at least one kind of metal ions selected from the group consisting of the ions of molybdenum, copper, silver, gold, palladium, tin, and antimony and/or at least one electrically conductive polymer selected from the group consisting of the polymer classes of the polyamines, polyanilines, polyimines, polythiophenes, and polypryrols.

There is provided a technique to strongly integrate a galvanized steel sheet and a resin molded article. A hot-dip galvanized steel sheet is immersed in an aqueous solution for aluminum degreasing to form a specific roughness on the surface. The surface is covered with convex protrusions having a diameter of about 100 nm, and a chromate treatment layer appears in the surface. A resin composition comprising 70 to 97 wt % of polyphenylene sulfide and 3 to 30 wt % of a polyolefin resin is injected onto the surface. The resin composition penetrates into ultra-fine irregularities and is cured in that state, and thereby a composite in which the galvanized steel sheet and the resin molded article are strongly integrated can be obtained. The shear rupture strength of the composite is extremely high.

A multistage method for treatment of composite metal structures containing metallic surfaces of aluminum, zinc and optionally iron, is provide wherein in a first step, selective zinc phosphating of zinc and ferrous surfaces proceeds using a phosphating solution containing a quantity of water-soluble inorganic silicon compounds sufficient to suppress white spot formation on zinc, but less than the quantity where zinc phosphating loses selectivity. In a following second step, aluminum surfaces are passivated with an acidic treatment solution. Also provided is a zinc phosphating solution suitable for said method containing at least 0.025 g/l, but less than 1 g/l of silicon as water-soluble inorganic compounds calculated as SiF.sub.6, wherein the product (Si/mM).Math.(F/mM) of the concentration of silicon [Si in mM] in the form of water-soluble inorganic compounds and the concentration of free fluoride [F in mM] divided by the free acid point number is no greater than 5.

Processes for the anti-corrosion pre-treatment of a plurality of components in series, in which each component in the series at least partly has surfaces of zinc and/or iron and at least parts of these surfaces are firstly activated in a targeted manner for subsequent zinc phosphating are provided with targeted activation achieved by means of controlled dispensing of an aqueous dispersion to wet zinc and/or iron surfaces, thus ensuring resource-saving activation; the aqueous dispersion for activation wetting contains a particulate constituent dispersed in water, which is at least partially composed of hopeite, phosphophyllite, scholzite and/or hureaulite and provided as a dispersion of these crystalline solids, stabilized by at least one polymeric organic compound; followed by a zinc phosphating bath comprising a quantity of an aqueous dispersion, in particular the same aqueous dispersion that is used for activation wetting.

The present invention belongs to the technical field of surface treatment for metal materials, and particularly relates to an environment-friendly water-based treatment agent for improving the phosphatability of high-strength steel. The water-based treatment agent is prepared by dissolving or dispersing a composition in an aqueous medium. The water-based treatment agent specifically consists of: A. a fluoride ion-containing compound; B. a compound selected from metal ion compounds containing Cu, Zn, Mn, Ni or Fe; C. a compound selected from organic acids; and D. a compound selected from surfactant. The water-based treatment agent can be diluted in water at a ratio of 1:0-20 for subsequent use. The treatment agent can enable the surface of a high-strength steel plate to have excellent phosphatability and is mainly applied to high-strength steel surface modification treatment.