Abstract: Copper can be directly chemically converted by the disclosed method and a novel copper-based metallic member is proposed. The chemical conversion film formed on the copper-based metallic member comprises phosphate and copper halide. The chemical conversion bath contains metal ions, phosphoric acid ions, halogen ions, and oxidizer.

Abstract: A conventional zinc phosphate chemical conversion film formed on an iron article comprises zinc phosphate hydrates, i.e., Zn.sub.3 (PO.sub.4).sub.2.4H.sub.2 O and Zn.sub.2 Fe(PO.sub.4).sub.2.4H.sub.2 O. A novel chemical conversion film is mainly composed of Zn.sub.3 (PO.sub.4).sub.2.2H.sub.2.4H.sub.2 O. The ratio of ##EQU1## is from 0.3 to less than 1. The problems of conventional chemical conversion film arise due to 4 moles of water of crystallization of the zinc phosphates which desiccates at a baking temperature of the paint. The small amount of water of crystallization of Zn.sub.3 (PO.sub.4).sub.2.2H.sub.2 O provides an improved chemical conversion film with respect to the corrosion resistance and the like.

Abstract: A method of forming a chemical phosphate coating on the surface of steel with a treatment bath made without directly adding any oxidizing agent such as nitrite ions or hydrogen peroxide, and maintaining its temperature in a range not exceeding 40.degree. C., its pH in the range of 2.5 to 4.5 and its oxidation-reduction potential (ORP in terms of the normal hydrogen electrode potential) in the range of 150 to 550 mV. The bath is formed from an aqueous solution of the two components, i.e. the first component, an acidic solution consisting mainly of oxo acid ions, such as, NO.sub.3.sup.-, phosphoric ions (H.sub.3 PO.sub.4 or H.sub.2 PO.sub.4.sup.-), and metal ions, such as Zn.sup.2+, and the second component, an alkaline solution containing hydroxide ions (OH.sup.-). Preferably, the bath has a temperature of 20.degree. C. to 30.degree. C., a pH value of 3.0 to 4.0 and an ORP of 350 to 450 mV.

Abstract: The present invention proposes a method for forming a chemical conversion phosphate film on the surface of steel, characterized in that the temperature of the conversion bath is from 0.degree. C. to 40.degree. C., the hydrogen-ion concentration (pH) of the conversion bath is in the range of from pH 2.2 to pH 3.5, and the oxidation reduction potential of the conversion bath is from 0 mV to 700 mV (normal hydrogen electrode potential).According to the present invention, normal-temperature phosphating and automatic bath control are attained.