Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
2002-04-19
2004-07-06
Oltmans, Andrew L. (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C148S247000, C148S259000, C148S260000
Reexamination Certificate
active
06758916
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
This invention relates to compositions and processes for treating metal surfaces with acidic aqueous compositions for forming conversion coatings on the metals; the conversion coatings provide excellent bases for subsequent painting. The invention is well suited to treating iron and steel, galvanized iron and steel, zinc and those of its alloys that contain at least 50 atomic percent zinc, and aluminum and its alloys that contain at least 50 atomic percent aluminum. Preferably the surface treated is predominantly ferrous; most preferably the surface treated is cold rolled steel.
This invention is very closely related to that disclosed in U. S. Pat. No. 5,449,415, from which it differs primarily in using a particularly advantageous type of water soluble and/or dispersible polymer. The object of this invention is to achieve better corrosion resistance under at least one set of corrosion promoting conditions than does the invention illustrated by examples in U.S. Pat. No. 5,449,415, without using any more hexavalent chromium in the process than is used in preferred examples in U.S. Pat. No. 5,449,415.
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, however. Also, throughout this description 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 the constituents of a mixture once mixed; specification of materials in ionic form implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole; any counterions thus implicitly specified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to an object of the invention; and the term “mole” and its variations means “gram-mole” and its variations and may be applied to elemental, ionic, hypothetical, unstable, and any other chemical species defined by number and type of atoms present, as well as to compounds with well defined molecules.
BRIEF SUMMARY OF THE INVENTION
It has been found that improved resistance to corrosion, particularly after subsequent conventional coating with an organic binder containing protective coating such as a paint or lacquer, can be imparted to active metal surfaces, particularly to iron and steel and other ferrous surfaces, by contacting the metal surfaces for a sufficient time at a sufficient temperature with an acidic aqueous composition as described in detail below. Such a composition differs from some preferred embodiments illustrated by example in U.S. Pat. No. 5,449,415 most markedly in the specific chemical nature of the substituents on the polymers of hydroxy styrene, modified by substitution on the aromatic rings of the polymers of substituted aminomethyl moieties, which are characteristic of both this invention and the preferred examples of U.S. Pat. No. 5,449,415. In the latter, at least one of the two substituents, exclusive of the single carbon atom that is bonded both to the amino nitrogen and the aromatic ring, on the amino nitrogen atom of each substituent moiety is a polyhydroxy moiety, but in the present invention both of these substituents jointly contain at least two carbon atoms and at least one hydroxy moiety but neither of these substituents on the amino nitrogen atoms individually contains more than half as many hydroxyl moieties as it has carbon atoms, unless it contains only one carbon atom. Preferably, the composition is coated over the metal surface to be treated and then dried in place on the surface of the metal, without intermediate rinsing.
Various embodiments of the Invention include working compositions for direct use in treating metals, concentrates from which such working compositions can be prepared by dilution with water, processes for treating metals with a composition according to the invention, and extended processes including additional steps that are conventional per se, such as precleaning, rinsing, and, particularly advantageously, painting or some similar overcoating process that puts into place an organic binder containing protective coating over the conversion coating formed according to a narrower embodiment of the invention. Articles of manufacture including surfaces treated according to a process of the invention are also within the scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
An acidic aqueous composition according to the invention comprises, preferably consists essentially of, or more preferably consists of, water and:
(A) a component of “fluorometallate” anions, each of said anions consisting of (i) at least four fluorine atoms, (ii) at least one atom of an element selected from the group consisting of titanium, zirconium, hafnium, silicon, aluminum, and boron, and, optionally, one or both of (iii) ionizable hydrogen atoms, and (iv) one or more oxygen atoms; preferably the anions are fluorotitanate (i.e., TiF
6
−2
) or fluorozirconate (i.e., ZrF
6
−2
), most preferably fluorotitanate;
(B) a component of divalent or tetravalent cations of elements selected from the group consisting of cobalt, magnesium, manganese, zinc, nickel, tin, copper, zirconium, iron, and strontium; independently preferably at least, with increasing preference in the order given, 60, 70, 80, 85, 90, 95, or 99% by weight of the total of component (B) consisting of divalent manganese, cobalt, nickel, or magnesium, more preferably of divalent manganese, cobalt, or nickel; most preferably of divalent manganese;
(C) a component of phosphorus-containing Inorganic oxyanions and/or phosphonate anions; and
(D) a component of water-soluble and/or water-dispersible polymers of vinyl phenol having at least mono-substituted aminomethyl moieties as substituents on the aromatic rings of said polymers; and, optionally, one or more of the following components:
(E) a dissolved oxidizing agent, preferably a peroxy compound, more preferably hydrogen peroxide;
(F) a component selected from the group consisting of tungstate, molybdate, silicotungstate, and silicomolybdate anions; and
(G) a component selected from dissolved or dispersed complexes stabilized against settling, said complexes resulting from reaction between:
“fluorometallate” anions, each of said anions consisting of (i) at least four fluorine atoms, (ii) at least one atom of an element selected from the group consisting of titanium, zirconium, hafnium, silicon, aluminum, and boron, and, optionally, one or both of (iii) ionizable hydrogen atoms, and (iv) one or more oxygen atoms and
one or more materials selected from the group consisting of metallic and metalloid elements and the oxides, hydroxides, and carbonates of these metallic or metalloid elements
to produce a reaction product that is not part of any of components (A) through (F) as recited above; preferably this component results from reaction with silica or vanadium(V) oxide.
It should be understood that the components listed need not necessarily all be provided by separate chemicals. For example, “fluorometallate” salts of protonated polymer molecules of component (D) can be used
Cameron Mary K.
Harper Stephen D.
Henkel Corporation
Oltmans Andrew L.
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