Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Reexamination Certificate
2000-12-22
2002-04-09
Cameron, Erma (Department: 1762)
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
C427S419100, C148S240000, C148S243000, C148S275000
Reexamination Certificate
active
06368671
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
This invention relates to a process for treating a solid surface with two successive distinct treatment liquids in order to improve at least one of the hydrophilicity of the surface, its corrosion resistance, and the adhesion to the treated surface by subsequently applied paints. The solid surface treated is preferably a metallic surface and more particularly a surface of aluminum or one of its alloys that contains at least 50 atomic percent of aluminum, all of these being hereinafter included within the meaning of the word “aluminum” and,
mutatis mutandis,
within the meaning of any grammatical variations of this word. The treatment compositions do not require hexavalent chromium but are capable of providing a quality of treated surface as good as that achieved in the past by treatments that did use hexavalent chromium, which is increasingly undesirable because of its adverse environmental impact. The invention is particularly advantageously applicable to provide aluminum evaporators, heat exchangers, and condensers with hydrophilic coatings that have good corrosion resistance and little or no tendency to develop undesirable odors during use.
Although any of the common structural metals can be used in constructing practical heat exchanging surfaces, aluminum and its alloys are among those most often used, because of their high heat conductivity. In heat exchanger surfaces, metals are normally used without any relatively thick protective coating such as a paint or lacquer that would generally be used in other types of equipment made from metals and exposed to corrosive environments, to improve the resistance of the equipment, but any such relatively thick protective coating is avoided in heal exchangers because such a coating would also reduce the efficiency of heat exchange.
During the cooling of hot air, a common use of these heat exchangers, moisture contained as vapor in the hot air condenses and initially forms water drops or beads on the fins of the heat exchanger. If the surface of the heat exchanger fins is not sufficiently hydrophilic, these water beads accumulate on the fin surface and tend to bridge across the small spaces between fins, thereby impeding the air flow between fins and reducing the heat transfer efficiency. The condensed water beads also tend to absorb dust and contaminants in the air, such as carbon dioxide, nitrogen oxides, and sulfur oxides, which can promote corrosion of the underlying aluminum, and because of the capillary forces holding in place water drops that have grown sufficiently large to bridge between adjacent fins, the normal drainage of water away from the fins that would otherwise carry away these absorbed contaminants is substantially reduced. Therefore, the formation of water beads on the fins of an aluminum heat exchanger not only decreases heat transfer efficiency but also can physically damage the exchanger.
In order to achieve a desirable combination of a hydrophilic nature and corrosion resistance on metal, particularly aluminum, surfaces, various coatings and treatments have been tried, but no fully satisfactory result has yet been achieved. A chromate conversion coating without any post-treatment usually has inadequate corrosion resistance and often develops an unpleasant odor and poor hydrophilicity. Silicate coating over a chromate conversion coat has often been used but has not satisfied all users. More recently, biocide protected hydrophilic organic polymer films have been used as post-treatments over chromate conversion coatings. While effective, these have proved to be expensive and difficult to control in some commercial operations.
Major alternative or concurrent objects of the invention are to achieve (i) a combination of adequate hydrophilicity and corrosion resistance, compared with the prior art, while minimizing the use of polluting constituents, particularly chromium, and of highly volatile constituents, particularly organic solvents, with potential toxicity or unpleasant odors for workers, in the treatment compositions, (ii) durability of the hydrophilicity under thermal aging and/or practical use, (iii) avoidance of the development of unpleasant odors during practical use of the hydrophilicized surfaces, (iv) improved corrosion resistance of the treated surface, even if it is not necessarily hydrophilic, and (v) improved adhesion of paints to the treated surfaces. Other objects will be apparent from the description below.
Except in the claims and the specific 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, 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 first definition or description of the meaning of a word, phrase, acronym, abbreviation or the like applies to all subsequent uses of the same word, phrase, acronym, abbreviation or the like and applies,
mutatis mutandis,
to normal grammatical variations thereof; 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; chemical descriptions of neutral materials apply to the materials at the time of addition to any combination specified in the description and/or of generation in situ in a combination by chemical reactions described in the specification, and do not necessarily preclude chemical changes to the materials as a result of unstated reaction in the combination; in addition, specification of materials in ionic form means that the materials are supplied to prepare the compositions containing them in the form of one or more soluble substance(s) containing the ions specified and implies the presence in any composition specified to contain ionic materials of sufficient counterions to produce electrical neutrality for the composition as a whole; 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 counternons that act adversely to an object of the invention; the description of liquid materials as “solution” or as “homogeneous” or by any grammatical variations of these terms includes not only true thermodynamic equilibrium solution or homogeneity but also dispersions that are stable enough to avoid any separation into two or more distinct phases readily detectable by unaided normal human vision after storage without mechanical disturbance at 25° C. for at least 100, or preferably at least 1000, hours; and the term “paint” and its grammatical variations include any similar materials that might be known by more specialized names such as enamel, lacquer, varnish, shellac, radiation curable coatings, photocurable coatings, primer, top coat, electrodeposited coatings, autodeposited coatings, or the like.
BRIEF SUMMARY OF THE INVENTION
It has been found that, in one major process embodiment of the invention, an effective treatment can be achieved by successive intervals of contact with an initial treatment liquid that comprises water and dissolved, dispersed, or both dissolved and dispersed polymers that include substantial mass fractions of benzene rings that are substituted with at least one oxygen atom and at least one substituted aminomethylene moiety on each ring, followed by treatment with a secondary treatment liquid that comprises water and vanadate anions. Other embodiments of the invention include an article of manufacture comprising a surface treated according to the invention and an extended process including a simple process according to
Cameron Erma
Harper Stephen D.
LandOfFree
Treating solid, especially aluminum, surfaces does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Treating solid, especially aluminum, surfaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Treating solid, especially aluminum, surfaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2888265