Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Patent
1995-06-16
1999-09-07
Simmons, David A.
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
148274, 148275, 148277, 148285, C23C 2248
Patent
active
059481781
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to compositions and processes for forming a protective coating on metal, particularly aluminum and/or aluminum alloy, surfaces. The coating formed is solid and adherent, often although not always colored, provides good corrosion protection to the metal surface, and functions as an excellent base for painting or similar organic based protective coatings. The coatings formed, when applied to substrates of aluminum and its alloys, usually impart as much corrosion protection as do conventional coatings formed by use of hexavalent chromium containing compositions, but the compositions and processes according to this invention cause less potential environmental dam-age because they do not need hexavalent chromium or other identified major pollutants.
1. Discussion of Related Art
The art believed to be most closely related is that described in WO94/00619, particularly Table II thereof This reference teaches that high quality coatings can be formed on metal substrates by contacting them with aqueous compositions believed to contain cobalt(III) complex anions formed by reaction among cobalt(II) salts, carboxylate ions, and various other ions in the presence of an oxidizing agent. Other closely related art includes U.S. Pat. No. 3,905,838 of Sep. 16, 1975 to Ito and U.S. Pat. No. 5,298,092 of Mar. 29, 1994 to Schriever.
Many of the compositions taught in this related art, although they have avoided the use of hexavalent chromium and other pollutants of the general environment, nevertheless can have adverse environmental impacts on the immediate working area for the process and any workers in this area. For example, many of the formulations previously used include high concentrations of ammonia, which causes at least a severe odor nuisance and possibly a serious health hazard to workers in the vicinity, unless expensive ventilation equipment is installed in the process area. Furthermore, the concentration of ammonia in aqueous solutions is difficult to maintain constant, as is desirable for achieving the most consistent results from the process, at the high levels previously recommended by some related art. In addition, some of the previously recommended compositions contain both nitrite ions and amines, which are generally believed to be readily capable of reacting to form nitrosamines, many of which are known carcinogens.
DESCRIPTION OF THE INVENTION
One major object of the invention is to provide compositions and processes that have reduced adverse environmental impact compared with related previously recommended processes as described above. Another alternative object is to provide more economical compositions and processes than those previously recommended, in particular by at least one of the following means: (i) reducing the treatment time required to form an effective protective coating and (ii) lowering the concentrations of active ingredients. Still another alternative object is to provide coatings with higher corrosion resistance, as formed and/or after subsequent painting or the like.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word "about" in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary: percent, "parts of", and ratio values are by weight; the term "polymer" includes oligomer; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred, description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among
REFERENCES:
patent: 3905838 (1975-09-01), Ito
patent: 4963596 (1990-10-01), Lindert et al.
patent: 5089064 (1992-02-01), Reghi
patent: 5226976 (1993-07-01), Carlson et al.
patent: 5268042 (1993-12-01), Carlson
patent: 5281282 (1994-01-01), Dolan et al.
patent: 5298092 (1994-03-01), Schriever
patent: 5342456 (1994-08-01), Dolan
patent: 5551994 (1996-09-01), Schriever
F.A. Cotton & G. Wilkinson, Advanced Inorganic Chemistry, 4th Ed., (John Wiley & Sons, New York, 1980), p. 712.
Carlson Lawrence R.
Dolan Shawn E.
Pierce John R.
Henkel Corporation
Jaeschke Wayne C.
Jaeschke, Jr. Wayne C.
Koehler Robert R.
Simmons David A.
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