A method of treating the surface of a metallic workpiece comprising the steps of: a) providing a surface of at least one metal, of at least one alloy or of a mixture of them, whereby at least one of the metals and alloys is anodizable that is used as an electrode; b) contacting said metallic surface with an anodizing solution; c) providing at least one other electrode in contact with said anodizing solution; and d) passing an electric current between said metallic surface and said other electrode through said anodizing solution, whereby micro-plasma arcs are provided as controlled micro-sparking regime, whereby the micro-plasma arcs do not provide significant break-downs in the anodizing coating and whereby the current density is ≤ 10 A per dm 2 of metallic surface to be coated; and e) wherein said anodizing solution is an aqueous solution having a pH greater than 7 and comprising: i. phosphorus and oxygen containing anions; ii. at least one water-soluble inorganic hydroxide; iii. at least one surfactant; and iv. at least one alcohol showing at least one alkaline radical group, which alcohol is selected from the group consisting of alkaline compounds showing at least one amido group, at least one amino group, at least one imino group, at least one imido group, at least one ureido group or any mixture of them, or at least one alkaline hydrolyzed silane or a mixture of them. a) providing a surface of at least one metal, of at least one alloy or of a mixture of them, whereby at least one of the metals and alloys is anodizable that is used as an electrode; b) contacting said metallic surface with an anodizing solution; c) providing at least one other electrode in contact with said anodizing solution; and d) passing an electric current between said metallic surface and said other electrode through said anodizing solution, whereby micro-plasma arcs are provided as controlled micro-sparking regime, whereby the micro-plasma arcs do not provide significant break-downs in the anodizing coating and whereby the current density is ≤ 10 A per dm 2 of metallic surface to be coated; and e) wherein said anodizing solution is an aqueous solution having a pH greater than 7 and comprising: i. phosphorus and oxygen containing anions; ii. at least one water-soluble inorganic hydroxide; iii. at least one surfactant; and iv. at least one alcohol showing at least one alkaline radical group, which alcohol is selected from the group consisting of alkaline compounds showing at least one amido group, at least one amino group, at least one imino group, at least one imido group, at least one ureido group or any mixture of them, or at least one alkaline hydrolyzed silane or a mixture of them. i. phosphorus and oxygen containing anions; ii. at least one water-soluble inorganic hydroxide; iii. at least one surfactant; and iv. at least one alcohol showing at least one alkaline radical group, which alcohol is selected from the group consisting of alkaline compounds showing at least one amido group, at least one amino group, at least one imino group, at least one imido group, at least one ureido group or any mixture of them, or at least one alkaline hydrolyzed silane or a mixture of them.