Multistage process for coating components having steel surfaces with corrosion protection

A process for the corrosion-protection treatment of components in series, which components comprise surfaces of steel, wherein each component in the series undergoes successive treatment stages i)-iii):

• i) conversion treatment stage, comprising contacting each component with an acidic aqueous composition containing
• a. at least 0.05 mmol/kg of fluoro complexes of the elements Zr and/or Ti, calculated as the amount of the elements Zr and/or Ti, and
• b. an amount of free fluoride;
• ii) rinsing stage, comprising one or more rinsing steps immediately following one another, wherein at least one rinsing step is carried out by contacting each component with an aqueous composition containing at least 1000 mg/kg but not more than 5000 mg/kg of hydrogen peroxide;
• iii) coating stage, comprising dip-coating by contacting each component with an aqueous dispersion of an organic binder;
• wherein immediately after the rinsing stage ii) a wet film remains on the surfaces of steel and contains hydrogen peroxide in an amount of at least 50 mg/kg relative to mass of said wet film;
• wherein the aqueous composition of the last rinsing step of the rinsing stage ii), comprises:
• (a) in each case less than 10 mg/kg of compounds of the metals Bi, Ni, Co and/or Cu dissolved in water calculated as the amount of the respective element in the aqueous composition,
• (b) a total of less than 100 mg/kg, of organic compounds,
• (c) a total of less than 100 mg/kg, of compounds of the element Si, dissolved in water;
• (d) a total of less than 20 mg/kg, of compounds of the elements Zr and/or Ti dissolved in water,
• (e) a total of less than 50 mg/kg each, of sodium and/or potassium ions,
• (f) a total of less than 10 mg/kg, of zinc ions, and/or
• (g) a total of less than 100 mg/kg, of phosphates dissolved in water;
• wherein the components of the series have zinc surfaces in addition to steel surfaces, and before the conversion treatment stage i) each component of the series first undergoes an alkali treatment stage, wherein, within the alkali treatment stage in at least one treatment step, at least the surfaces of steel and zinc of the components of the series are brought into contact with an alkaline aqueous composition, which contains at least 50 mg/kg of iron (III) ions, at least 100 mg/kg of phosphate ions, and wherein the alkaline aqueous composition has a free alkalinity of at least 1 point and a pH of at least 10.5.