Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
2002-09-20
2003-09-16
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C148S261000, C106S014120
Reexamination Certificate
active
06620263
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a process for forming a zinc-containing phosphate conversion coating layer on an active metal surface, more particularly a surface selected from the group consisting of (i) steel and other non-passivating ferrous alloys that contain at least 50% by weight of iron, (ii) galvanized steel, (iii) other surfaces of zinc or its alloys that contain at least 50% by weight of zinc; and (iv) aluminum and its alloys containing at least 50% by weight of aluminum.
It is well known that zinc phosphate conversion coatings, particularly those of the modem “low zinc” type, are capable of producing excellent corrosion-protective under-coatings for subsequent painting. It has been generally regarded in the prior art that two of the important characteristics of a “low zinc” phosphating liquid composition are a phosphate concentration of at least 5 grams per liter of composition, this unit of concentration being hereinafter usually abbreviated as “g/l”, more preferably at least 10 g/l, and a weight ratio of phosphate to zinc concentrations that is at least 10:1. Processes that use such phosphating compositions produce a substantial volume of effluent water containing phosphate, which in most jurisdictions is a pollutant that must be abated. An object of this invention is to provide phosphating processes that utilize compositions with lower contents of pollutants but still achieve satisfactory corrosion resistance as undercoats for paint.
Except in the claims and the operating examples, or where otherwise expressly indicated to the contrary, 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 the description and claims, 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, 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, and any counterions thus implicitly specified preferably are 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 its grammatical variations includes any more specialized types of protective exterior coatings that are also known as, for example, lacquer, electropaint, shellac, top coat, base coat, color coat, and the like; and the term “mole” and its variations may be applied to ionic, chemically unstable neutral, or any other chemical species, whether actual or hypothetical, that is specified by the type(s) of atoms present and the number of each type of atom included in the unit defined, as well as to substances with well defined neutral molecules.
BRIEF SUMMARY OF THE INVENTION
It has been found that with proper control of other characteristics of the phosphating composition and process, fully satisfactory underpaint corrosion resistance can be obtained from conversion coatings formed by a phosphating composition with smaller concentrations of phosphate and ratios of phosphate to zinc than has heretofore been taught. The pollution potential of the phosphating compositions is correspondingly reduced. On some substrates, the corrosion resistance is actually improved over that obtained with current conventional processes using otherwise similar phosphating compositions with higher concentrations of phosphate
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
A working phosphating composition according to the invention comprises, preferably consists essentially of, or more preferably consists of water and the following components:
(A) a component of dissolved phosphate anions that have a concentration in the working composition that is not more than, with increasing preference in the order given, 13, 10, 9.5, 9.0, 8.5, 8.0, 7.5, 7.0, 6.5, and at least for economy still more preferably is not more than 6.0, 5.5, 5.0, 4.5, 4.0, 3.5, 3.0, or 2.5 g/l and independently preferably is at least, with increasing preference in the order given, 0.5, 1.0, 1.5, 1.7, 1.9, or 2.0 g/l;
(B) a component of dissolved zinc cations that have a concentration in the working composition that is at least, with increasing preference in the order given, 0.30, 0.40, 0.50, 0.60, 0.70, 0.75, 0.80, 0.85, 0.90, 0.93, 0.95, or 0.97 g/l and independently preferably is not more than, with increasing preference in the order given, 2.0,1.8, 1.6, 1.50, 1.40, 1.35, 1.30, 1.25, 1.20, 1.15, 1.10, 1.05, or 1.00 g/l; and
(C) a component of dissolved manganese(II) cations that have a concentration in the working composition that is at least, with increasing preference in the order given, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, or 0.48 and independently preferably is not more than, with increasing preference in the order given, 2.0, 1.5, 1.2, 1.0, 0.90, 0.80, 0.75, 0.70, 0.65, 0.60, 0.55, or 0.50;
and, optionally, one or more of the following components:
(D) a component of at least one of:
dissolved nickel(II) cations that have a concentration in the working composition that is at least, with increasing preference in the order given, 0.10, 0.20, 0.30, 0.40, 0.50, or 0.60 g/l and independently preferably is not more than, with increasing preference in the order given, 2.0,1.5,1.3, or 1.1 g/l; and
dissolved copper cations that have a concentration that is at least, with increasing preference in the order given, 0.0001, 0.0003, 0.0005, 0.0007, 0.0009, 0.0011, 0.0013, 0.0015, 0.0017, 0.0019, or 0.0021 g/l and independently preferably is not more than, with increasing preference in the order given, 0.030, 0.025, 0.020, 0.015, 0.010, or 0.070 g/l;
(E) a component of dissolved fluorine-containing anions that have a stoichiometric equivalent as fluoride that is at least, with increasing preference in the order given, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, or 0.55 g/l and independently preferably is not more than, with increasing preference in the order given, 2.0, 1.5, 1.2, 1.0, 0.90, or 0.80 g/l;
(F) a component of dissolved nitrate ions that have a concentration in the working composition that is at least, with increasing preference in the order given, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, or 3.9 g/l and independently, at least for economy, preferably is not more than, with increasing preference in the order given, 20, 15, 12, 10, or 8.8 g/l; and
(G) a dissolved accelerator component consisting of at least one substance selected from the group consisting of:
0.3 to 4 g/l of chlorate ions;
0.01 to 0.2 g/l of nitrite ions;
0.05 to 2 g/l of m-nitrobenzene sulphonate ions;
0.05 to 2 g/l of m-nitrobenzoate ions;
0.05 to 2 g/l of p-nitrophenol;
0.005 to 0.15 g/l of hydrogen peroxide in free or bound form;
0.1 to 10 g/l of hydroxylamine in free or bound form; and
0.1 to 10 g/l of reducing sugar.
If the composition has an initial pH value lower than 3.80+0.03, it has positive Free Acid points which are quantitatively defined as equal to the number of milliliters (hereinafter usually abbreviated as “ml”) of 0.100 N strong alkali required to titrate a 10.0 ml sample of the composition to a pH value of 3.80±0.03; if the initial value of pH of the composition
Cameron Mary K.
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Oltmans Andrew L.
Sheehan John
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