Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Patent
1996-10-25
1999-02-09
Simmons, David A.
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
148251, 148253, 148261, 148275, C23C 2248
Patent
active
058688722
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
Statement of Related Art
This invention relates to the preparation of cleaned metal surfaces, more particularly strips of aluminum or aluminum alloys, for the subsequent application of organic coatings, particularly for the manufacture of metal goods for architectural applications and for the food packaging industry.
So-called "no-rinse" processes are generally known in the chemical treatment of metal surfaces, for example for the subsequent application of paints, adhesives and/or plastics. In no-rinse processes, the metal surfaces are freed from oil, dirt and other residues in a first stage. Any residues of chemicals from this first stage are removed by rinsing with water. In the next stage of the process, the clean metal surface is wetted with an aqueous bath solution which is not rinsed off, but instead is dried in situ on the metal surface and, in the process, is converted into a solid film of the bath ingredients. Coatings such as these can significantly improve the surface quality of covering layers subsequently applied, particularly with respect to corrosion control and adhesion. Originally, treatment solutions containing hexavalent chromium ("yellow chromating") were often proposed in the extensive relevant prior art literature. On account of the toxic character of Cr(VI), these processes or rather the rinsing waters accumulating therein require expensive wastewater treatment. Even processes which only use trivalent chromium (DE-A-32 47 729) were not entirely satisfactory on account of increasing demands for the complete absence of chromium.
The chromium-free conversion treatment of aluminum surfaces with fluorides of boron, silicon, titanium or zirconium alone or in conjunction with organic polymers for obtaining permanent protection against corrosion and for producing a base for subsequent painting is known in principle:
U.S. Pat. Nos. 5,129,967 and 4,921,552 disclose treatment baths for the no-rinse treatment (described there as "dried in place conversion coating") of aluminum containing:
EP-B-8 942 discloses treatment solutions, preferably for aluminum cans, containing: TiF.sub.6 and H.sub.2 SiF.sub.6, the pH value of the solution being below 3.5, containing: TiF.sub.6 and H.sub.2 SiF.sub.6 and
DE-C-24 33 704 describes treatment baths for increasing paint adhesion and permanent protection against corrosion inter alia on aluminum which may contain from 0.1 to 5 g/l of polyacrylic acid or salts or esters thereof and 0.1 to 3.5 g/l of ammonium fluorozirconate, expressed as ZrO.sub.2. The pH values of these baths may vary over a wide range. The best results are generally obtained when the pH value is in the range from 6 to 8.
U.S. Pat. No. 4,992,116 describes treatment baths for the conversion treatment of aluminum with pH values of around 2.5 to 5 which contain at least three components, namely:
a) phosphate ions in a concentration of 1.1.times.10.sup.-5 to 5.3.times.10.sup.-3 moles/l, corresponding to 1 to 500 mg/l, element of the group consisting of Zr, Ti, Hf and Si (corresponding to 1.6 to 380 mg/l, depending on the element) and poly(vinylphenol) with aldehydes and organic amines.
WO 92/07973 describes a chromium-free treatment process for aluminum which uses 0.01 to around 18% by weight of H.sub.2 ZrF.sub.6 and 0.01 to around 10% by weight of a 3-(N--C.sub.1-4 -alkyl-N-2-hydroxyethylaminomethyl)-4-hydroxystyrene polymer as essential components in the form of an acidic aqueous solution.
German patent application P 43 17 217.2 describes a process for the pretreatment of surfaces of aluminum or its alloys before a second conversion treatment for permanent corrosion control, in which the surfaces are contacted with acidic aqueous treatment solutions which contain complex fluorides of the elements boron, silicon, titanium, zirconium or hafnium either individually or in admixture with one another in concentrations of the fluoroanions of, in total, 100 to 4,000 and preferably 200 to 2,000 mg/l and which have a pH value of 0.3 to 3.5 and preferably in the range from 1 to 3.
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Karmaschek Uwe
Mady Raschad
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Koehler Robert R.
Simmons David A.
Szoke Ernest G.
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