Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Forming nonelectrolytic coating after forming nonmetal...
Reexamination Certificate
2000-05-17
2002-09-10
Wong, Edna (Department: 1764)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Forming nonelectrolytic coating after forming nonmetal...
C205S204000, C148S272000, C148S276000
Reexamination Certificate
active
06447665
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to compositions and processes for sealing oxide layers formed by anodization on surfaces of aluminum and its alloys containing at least 75 atomic percent of aluminum; both the pure metal and alloys are designated hereinafter simply as “aluminum”, unless the context requires otherwise. The anodization that precedes use of a process according to this invention is itself conventional and not in general the subject of this invention, although as noted below the invention is particularly advantageously applicable to surfaces formed by anodization under particular conditions.
It is generally known in the anodization art that for most practical uses the coatings initially formed on aluminum by anodization need to be “sealed” before use in order to have a long service life, presumably because the initially formed coatings have micropores that extend from the outer surface nearly to the original metal surface. Steam and hot water have commonly been used for sealing since early in the development of the art and generally are still technically satisfactory but slow. Various additives that improve properties in specific sealing circumstances, conserve energy by giving satisfactory sealing at lower temperatures, reduce pollution by replacing previously used materials with high pollution potential with other materials less damaging to the environment, and/or reduce the time required for sealing are known in the prior art, but further improvements along these lines, particularly reductions in total process time and/or in use of pollutants, are still desirable and are the general objects of this invention. Other more specific objects of the invention 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 andlor 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, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight or mass; the term “polymer” includes “oligomer”, “copolymere”, “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 within the composition by chemical reaction(s) noted in the specification between one or more newly added constituents and one or more constituents already present in the composition when the other constituents are added, and does not necessarily preclude unspecified chemical interactions among the constituents of a mixture once mixed; specification of constituents in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole and for any substance added to the composition; 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 an object of the invention; the word “mole” means “gram mole”, and the word itself and all of its grammatical variations may be used for any chemical species defined by all of the types. and numbers of atoms present in it, irrespective of whether the species is ionic, unstable, hypothetical, or in fact a stable electrically neutral substance with well defined molecules; and the terms “solution”, “soluble”, “homogeneous”, and the like are to be understood as including not only true equilibrium solutions or homogeneity but also dispersions that show no visually detectable tendency toward phase separation over a period of observation of at least 100, or preferably at least 1000, hours during which the material is mechanically undisturbed and the temperature of the material is maintained within the range of 18-25° C.
SUMMARY OF THE INVENTION
It has been found that at least one object, and in preferred embodiments two or more objects, of the invention as stated above can be achieved by a two step process in which the first step is exposure of the anodized surface to be sealed to an aqueous solution containing lithium cations and fluoride anions at a relatively low temperature, followed by a short treatment with a different treatment composition at a higher temperature than the second step. The pH and silicon content of the aqueous solution used for the first treatment step are carefully controlled to achieve consistently satisfactory results. Compositions for use according to process embodiments of the invention, concentrate compositions from which such compositions for use can be made by mixing and dilution with water, and articles of manufacture treated by a process according to the invention are also within the scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Preferred compositions for use in a first step of sealing according to the invention comprise, preferably consist essentially of, or more preferably consist of, water and:
(A) a concentration of dissolved lithium cations; and
(B) a concentration of dissolved fluoride ions; and, optionally, one or more of the following components:
(C) a component of one or more dissolved, dispersed, or both dissolved and dispersed surfactants;
(D) a component of dissolved pH controlling agent that is not part of any of components (A), (B), and (C);
(E) a component of preservative material that is not part of any of components (A), (B), (C), and (D);
(F) not more than 5.0 parts of silicon per million parts by weight of the total composition, a concentration unit which may be applied to other constituents as well as silicon and is hereinafter usually abbreviated as “ppm”, in any dissolved or suspended chemical form;
(G) up to 2000 ppm of complex transition metal containing anions, said anions not being part of any of components (A) through (F) as recited above and being selected from the group consisting of simple and condensed molybdates, tungstates, and vanadates; and
(H) up to 1000 ppm of polymers that are not part of any of components (A) through (G), said polymers being selected from the group consisting of homo- and co-polymers of at least one of acrylic acid, methacrylic acid, and maleic acid, all optionally bearing phosphonic acid substituents.
Component (A) may be derived from any sufficiently water soluble lithium salt, including the fluoride, which would also supply component (B). However, the preferred concentrations of components (A) and (B) are such that if lithium fluoride, with a water solubility of only about 1 part per thousand by weight, is used as the source of component (A), only slight dilution of a saturated solution is possible without reducing the concentration of at least one of components (A) and (B) below the most preferred level. Furthermore, if the solid salt is used as a source of components (A) and (B), it may be slow to dissolve, and the relatively small amounts of it needed may be difficult to measure and control accurately enough at the point of use. Still further, the most preferred ratio between fluoride and lithium concentrations is lower than that in lithium fluoride salt. For all of these reasons, the normally preferred source of component (A) is lithium acetate, which is relatively inexpensive and very soluble in water, so that concentrates can easily be prepared, and/or lithium hydroxide, which is also relatively inexpensive and sufficiently soluble in water to make useful concentrates, even though it is much less soluble than lithium acetate.
A concentrate composition accor
Carlson Lawrence R.
Johnson Philip M.
Wojciechowski Scott A
Harper Stephen D.
Henkel Corporation
Ortiz Daniel S.
LandOfFree
Faster two-step sealing of anodized 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 Faster two-step sealing of anodized aluminum surfaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Faster two-step sealing of anodized aluminum surfaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2866697