Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
2002-02-15
2004-05-11
Oltmans, Andrew L. (Department: 1742)
Stock material or miscellaneous articles
Composite
Of metal
C428S472100, C428S472300, C148S247000, C148S251000, C148S256000, C148S257000, C148S262000, C427S327000
Reexamination Certificate
active
06733896
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to treating multi-metal articles using a two-step coating system and to metal articles coated in accordance with the two-step process. More particularly, the present invention relates to a two step process for treating one or more multi-metal articles with a first coating composition suitable for forming a conversion coating on steel- and zinc-based metals, followed by a second coating composition suitable for forming a conversion coating on aluminum-based metal, and to multi-metal articles so treated. More particularly, the present invention relates to treating one or more multi-metal articles in a conversion coating line with a phosphate coating composition and a ceramic composite coating composition.
2. Background Art
Applying conversion coatings, in general, is a well-known method of providing metals and their alloys with one or more layers or coatings that impart increased corrosion resistance and adhesion of subsequently applied finishes/coatings (i.e., paints, lacquers, varnishes, etc.) to the metals. Many metal line treatment processes contain a plurality of multi-metal articles. By multi-metal articles, it is meant (1) an article that has surfaces of steel- and/or zinc-based metal along with surfaces of aluminum-based metal, (2) at least a first article that has surfaces of steel- and/or zinc-based metal and at least a second article that has surfaces made of aluminum-based metal, or (3) both (1) and (2) described above. Historically, pre-treatment lines that have utilized predominately heavy metal substrates (i.e., typically having a line composition of less than 10-20% light metal such as aluminum-based metal) have practiced the art of zinc-phosphate conversion coating. The use of zinc-phosphate conversion coatings for treating metals that have been predominately heavy metals has been relatively successful. However, as light metal articles are becoming more common in automobiles and other products, the relative amount of, or percent of light metal articles requiring treatment has increased. In many instances, the percentage of the surface area of light metals in a treatment line can be as high as 75-85% or more of all the metal articles passing through the treatment line. It has been observed that zinc-phosphate conversion coating compositions have had difficulty in providing and maintaining a suitable conversion coating on aluminum-based surfaces when aluminum-based surfaces comprise a substantial, such as greater than 20-40%, proportion of the metal surfaces being processed/treated. This is because aluminum contamination removes fluoride and can aid in the precipitation of zinc-phosphate sludge, which can lower the zinc concentration.
Accordingly, it is an object of the present invention to provide a method for effectively treating one or more multi-metal articles, regardless of the relative amount of aluminum-based surfaces, and preferably where the surface area of the aluminum-based metal comprises greater than 20%, more preferable greater than 35%, and even more preferably greater than 60% of the total surface area of the sum of the multi-metal articles. It is also an object of the present invention to provide a multi-step coating method for effectively treating one or more multi-metal articles wherein prior coatings remain essentially undamaged by subsequent coatings.
SUMMARY OF THE INVENTION
It has been found that treating multi-metal articles by (i) exposing the articles to a phosphating composition capable of providing a conversion coating on steel- and zinc-based metals, and (ii) exposing the articles to a ceramic composite treatment comprising water and (A) a product of chemical interaction between (1) an amount, all of which is dissolved in the water, of a first initial reagent component selected from the group consisting of fluoroacids of the elements of titanium, zirconium, hafnium, boron, aluminum, silicon, germanium, and tin; and (2) an amount, which may be dissolved, dispersed or both dissolved and dispersed in the water, of a second initial reagent component selected from the group consisting of titanium, zirconium, hafnium, boron, aluminum, silicon, germanium, and tin and all of oxides, hydroxides, and carbonates of all of titanium, zirconium, hafnium, boron, aluminum, silicon, germanium, and tin is particularly effective in treating multi-metal articles passing through a treatment line over an extended period of time, regardless of the relative amount of aluminum-based surfaces passing through the treatment line.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is particularly useful in treating multi-metal articles made of one or more of steel-(iron) and/or zinc-based metals, and aluminum-based metal, especially where the surface area of the aluminum-based metal comprises greater than 20%, more preferably greater than 35%, and even more preferably greater than 50% of the total surface area of the sum of the multi-metal articles passing through a treatment line. The articles are treated in accordance with the present invention by treating the articles with a coating composition suitable for providing a conversion coating on steel- and zinc-based metals, followed by treating the metal articles with a conversion coating capable of providing a conversion coating on aluminum-based metal articles. Metals capable of being processed in accordance with the invention to provide coated articles having good resistance to corrosion include, but are not limited to, steel, galvanized steel, aluminum, aluminum alloys and galvanized aluminum.
The coating composition suitable for providing a conversion coating on steel- and zinc-based metal articles comprises a phosphating coating composition, and more preferably a zinc-phosphate coating composition or an iron-phosphating coating composition.
Suitable zinc-phosphate coating compositions and their manner of use include those disclosed in U.S. Pat. Nos. 4,961,794 and 4,838,957, the entire disclosures of which, except to the extent that they may be inconsistent with any explicit statement herein, are incorporated herein by reference.
Suitable iron-phosphating coating compositions and their manner of use include those disclosed in U.S. Pat. Nos. 5,073,196 and 4,149,909, the entire disclosures of which, except to the extent that they may be inconsistent with any explicit statement herein, are incorporated by reference.
A particularly preferred aqueous, acidic, zinc-phosphate composition usable with the invention comprises:
(a) from 0.1 to 1.5 g/l, preferably from 0.5 to 1.4 g/l of zinc ion;
(b) from 5 to 50 g/l, preferably from 10 to 30 g/l, of phosphate ion;
(c) from 0.2 to 4 g/l, preferably from 0.6 to 3 g/l, of manganese ion;
(d) at least 0.05 g/l, preferably from 0.1 to 3 g/l, of fluoride ion;
(e) less than 0.5 g/l of chloride ion, and
(f) a phosphating accelerator (conversion coating accelerator).
When the content of the zinc ion in the zinc-phosphate solutions usable in the invention is less than 0.1 g/l, an even phosphate film is not formed on the iron-based surfaces. When the zinc ion content exceeds 1.5 g/l in the zinc-phosphate solutions usable in the invention, then on both iron-based and zinc-based surfaces, continuing formation of the phosphate film occurs, causing a build-up of the film, with the result that the film shows a decrease in adhesion and becomes unsuitable as a substrate for cationic electrocoating.
When the content of phosphate ion in the zinc-phosphate solutions usable in the invention is less than 5 g/l, an uneven phosphate film is apt to be formed. When the phosphate ion content is more than 50 g/l in the zinc-phosphate solutions usable in the invention, no further benefits result, and it is therefore economically disadvantageous to use additional quantities of phosphate chemicals.
When the content of manganese ion is less than 0.2 g/l in the zinc-phosphate solutions usable in the invention, the manganese content in the phosphate film formed on zinc-based surfaces is very small; the
Carlson Lawrence R.
Dolan Shawn E.
Kay Michael J.
Brooks & Kushman P.C.
Henkel Corporation
Oltmans Andrew L.
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