Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
2001-10-10
2003-03-11
Green, Anthony (Department: 1755)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C106S014120, C106S014440, C148S243000, C148S253000, C148S261000
Reexamination Certificate
active
06530999
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the well known general field of phosphate conversion coating of metals and more particularly to phosphate coatings formed from a liquid phosphating composition that contains both zinc and at least one of nickel, cobalt, and manganese as layer forming cations. The coatings formed from such a phosphating composition normally contain both zinc and at least the one(s) of nickel, cobalt, and manganese also present in the phosphating compositions. These coatings may also contain iron, particularly if a ferriferous substrate such as ordinary (non-stainless) steel is being phosphated.
Phosphating compositions with a high total concentration of cations of divalent nickel, divalent cobalt, and/or divalent manganese (these three types of cations being hereinafter usually jointly referred to as “NCM”) along with zinc, as taught in U.S. Pat. No. 4,681,641 of Jul. 21, 1987 to Zurilla et al., often provide better corrosion resistance to the metal substrates covered with them than do almost any other kind of commonly used phosphating. The conversion coatings formed by the use of such a phosphating composition, when the composition has a very high nickel concentration, also have smaller crystal sizes than do the coatings produced by almost any other, kind of commonly used phosphating. However, phosphating processes with these compositions are also more prone to sludging and, when the total NCM content is very high, are much more prone to forming hard, heat-insulating scale on metal process equipment surfaces than almost any other type of commonly used phosphating process. Furthermore, phosphating solutions of the high NCM type are also much more expensive than almost any other type of phosphating composition, and this expense has limited their use.
Accordingly, a major object of this invention is to provide less expensive phosphating compositions and/or processes that produce conversion coatings with very fine crystal sizes comparable to those produced by previously known high NCM compositions. Alternative and/or concurrent objects are to reduce, or at least not to exceed, the sludge formation and/or scaling obtained with previously used high NCM phosphating. Further more detailed alternative and/or concurrent objects will be apparent from the description below.
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, throughout this description, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight; the term “polymer” includes “oligomer”, “copolymer”, “terpolymer”, and the like; 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 or of generation in situ by chemical reactions specified in the description, and does not necessarily preclude other chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form additionally 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 the objects of the invention); the term “paint” and all of its grammatical variations are intended to include any similar more specialized terms, such as “lacquer”, “varnish”, “electrophoretic paint”, “top coat”, “color coat”, “radiation curable coating”, or the like and their grammatical variations; and the term “mole” means “gram mole”, and “mole” and its grammatical variations may be applied to elemental, ionic, and any other chemical species defined by number and type of atoms present, as well as to compounds with well defined molecules.
SUMMARY OF THE INVENTION
It has surprisingly been found that the presence of small concentrations of cobalt cations together with concentrations of nickel and manganese considerably lower than in an otherwise conventional high NCM zinc phosphating composition makes it possible to obtain conversion coatings with the desirable very fine crystal size previously obtainable only with high NCM phosphating.
Embodiments of the invention include working aqueous liquid compositions suitable for contacting directly with metal surfaces to provide conversion coatings thereon; liquid or solid concentrates that will form such working aqueous liquid compositions upon dilution with water, optionally with addition of other ingredients; processes of using working aqueous liquid compositions according to the invention as defined above to form protective coatings on metal surfaces and, optionally, to further process the metal objects with surfaces so protected; protective solid coatings on metal surfaces formed in such a process; and metal articles bearing such a protective coating.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
A working composition according to the invention preferably comprises, more preferably consists essentially of, or still more preferably consists of, water and the following components:
(A) dissolved phosphate anions;
(B) dissolved cobalt cations;
(C) dissolved zinc cations; and
(D) at least one of dissolved nickel cations and dissolved manganese cations. Optionally, one or more of the following components may also be present:
(E) a phosphating accelerator that is not part of any of components (A) through (D) as recited immediately above;
(F) dissolved chelating molecules (for divalent metal cations) that are not part of any of components (A) through (E) as recited immediately above;
(G) an acidity adjustment agent that is not part of any of components (A) through (F) as recited immediately above;
(H) dissolved fluoride ions that are not part of any of components (A) through (E) as recited immediately above;
(J) dissolved iron cations; and
(K) sludge conditioner that is not part of any of components (A) through (J) as recited immediately above.
Additional optional components may also be present.
In a composition according to the invention, component (A) preferably, at least for economy, is sourced to a composition according to the invention by at least one of orthophosphoric acid and its salts of any degree of neutralization. Component (A) can also be sourced to a composition according to the invention by pyrophosphate and other more highly condensed phosphates, including metapho sphates, which tend at the preferred concentrations for at least working compositions according to the invention to hydrolyze to orthophosphates. However, inasmuch as the condensed phosphates are usually at least as expensive as orthophosphates, there is little practical incentive to use condensed phosphates, except possibly to prepare extremely highly concentrated liquid compositions according to the invention, in which condensed phosphates may be more soluble.
Whatever its source, the concentration of component (A) in a working composition according to the invention, measured as its stoichiometric equivalent as H
3
PO
4
with the stoichiometry based on equal numbers of phosphorus atoms, preferably is at least, with increasing preference in the order given, 0.2, 0.4, 0.6, 0.70, or 0.75% and independently preferably is not more than, with increasing preference in the order given, 20, 10, 6.5, 5.0, 4.0, 3.5, 3.0, 2.0, 1.8, 1.6, or 1.4%. If the phosphate concentration is too low, the rate of
Cuyler Brian B.
Meagher Kevin K.
Cameron Mary K.
Green Anthony
Harper Stephen D.
Henkel Corporation
Seifert Arthur G.
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