Method for treating metallic surfaces with an acidic aqueous composition to improve corrosion resistance
Described herein is a method for treatment of a metallic surface, including the step of contacting the metallic surface with an acidic aqueous composition. Also described herein is an acidic aqueous composition used in the method for treatment, a master batch to produce such acidic aqueous composition, a method of using the acidic aqueous composition to treat metallic surfaces and substrates including the thus treated metallic surfaces.
1. A method for treatment of a metallic surface, comprising the step of
contacting the metallic surface with an acidic aqueous composition, the acidic aqueous composition comprising
(a) one or more metal compounds (M) selected from the group of titanium compounds, zirconium compounds and hafnium compounds;
(b) one or more linear polymers (P), prepared by controlled radical polymerization, containing 85 to 95 mol-% of (m1) N, N-dimethyl (meth)acryl amide, and the rest being (m2) vinylphosphonic acid in form of their polymerized monomeric units, and
the one or more linear polymers (P) being comprised in the acidic aqueous composition in an amount of 10 to 500 ppm based on the total weight of the acidic aqueous composition; and
one or more hydrolysable organosilane compounds (S) or their hydrolysis products (HS) and/or condensation products (CS).
2. The method according to claim 1 , characterized in that the metallic surface contains or consists of one or more metals or alloys selected from the group consisting of zinc, steel, cold rolled steel, hot rolled steel, galvanized steel, hot-dip galvanized steel, aluminum, magnesium and zinc-magnesium alloys.
3. The method according to claim 2 , characterized in that the acidic aqueous composition has a pH in the range of 0.5 to 5.5.
4. The method according to claim 1 , characterized in that the one or more metal compounds (M) are the fluoro metallates of said metals and/or the one or more metal compounds (M) are comprised in the acidic aqueous composition in a concentration in the range of 20 to 1600 ppm.
5. The method according to claim 1 , characterized in that the one or more linear polymers (P) are comprised in the acidic aqueous composition in a concentration in the range of 20 to 250 ppm.
6. The method according to claim 1 , characterized in that the one or more hydrolysable organosilane compounds (S) or their hydrolysis products (HS) and/or condensation products (CS) are selected from the group consisting of organoalkoxysilanes, organosilanoles, polyorganosilanoles, organosiloxanes and polyorganosiloxanes and/or that the one or more hydrolysable organosilane compounds (S) or their hydrolysis products (HS) and/or condensation products (CS) are comprised in the acidic aqueous composition in a concentration in the range of 1 to 750 ppm.
7. The method according to claim 6 , characterized in that the organosilane compounds (S) or their hydrolysis products (HS) comprise at least one of the groups selected from the group consisting of amino groups, urea groups, imido groups, imino groups and ureidos group, and the one or more condensation products (CS) of the hydrolysable silane compounds (S) comprises the same number of the before mentioned groups per condensed unit of the hydrolysable silane compound (S) or its hydrolysis product (HS).
8. The method according to claim 1 , characterized in that the acidic aqueous composition further comprises (d) at least one kind of metal cation selected from the group consisting of cations of metals of the 1 st to 3 rd subgroup of the periodic table of elements, cations of metals of the 5 th to 8 th subgroup of the periodic table of the elements including lanthanides, the cations of metal in the 2 nd main group of the periodic table of the elements, lithium, bismuth and tin.
9. The method according to claim 8 , characterized in that the (d) at least one kind of metal cation is selected from the group consisting of the cations of zinc, copper, cerium and molybdenum and/or (d) at least one kind of metal cation is comprised in the acidic aqueous composition in a concentration in the range of 5 to 5000 ppm.
10. The method according to claim 1 , characterized in that the acidic aqueous composition further comprises e) one or more water-soluble fluorine compounds.
11. The method according to claim 10 , characterized in that the one or more water-soluble fluorine compounds is a water-soluble fluoride having free fluoride ions (F″) and the concentration of free fluoride in the acidic aqueous composition is in the range of 15 to 150 ppm.
12. An acidic aqueous composition as used in claim 1 .
13. A master batch to produce the acidic aqueous composition according to claim 12 by diluting the master batch with water and if applicable adjusting the pH value.
14. A method of using the acidic aqueous composition according to claim 12 , the method comprising using the acidic aqueous composition for treating a metallic surface.
15. The method according to claim 14 , characterized in that the method provides corrosion protection to the metallic surface and/or provides an increased adhesion of further coatings applied onto the thus treated metallic surface.
16. A substrate comprising a metallic surface, treated according to the method as defined in claim 1 , the substrate being selected from the group consisting of parts of motor vehicles, rail vehicles, aircrafts, spacecrafts, parts of apparatus and machines, furniture parts, parts used in the construction field, to produce guard railing, lamps, profiles, cover panels or small parts, autobodies and parts thereof, single or separate components, pre-assembled elements, for the manufacture of apparatus and constructions, for household aids, control units, testing equipment and construction elements.