Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Utilizing brush or absorbent applicator
Reexamination Certificate
1998-11-02
2001-11-06
Mayekar, Kishor (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Utilizing brush or absorbent applicator
C205S178000, C205S268000
Reexamination Certificate
active
06312580
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for plating gold on chromium and particularly onto the passive plated chromium services of automobile emblems,and one step.
Chromium electroplated deposits exhibit a bright, silver-like luster, and are used extensively for plating automobile bumpers and hardware, e.g., plumbing fixtures, which exploit the decorative “white” luster of this hard and corrosion-resistant metal. Thus one authority on chromium plating has stated, “thin coatings serve as a non tarnishing, durable surface finish” with respect to decorative plating; and “heavy coatings are used to take advantage of the special properties of chromium, including resistance to heat, wear corrosion, and erosion, and low coefficient of friction” (George Dubpernell,
Modem Electroplating
, Frederick Lowenheim, Editor, John Wiley 1974 p.87) with respect to hard industrial finishes. However, it is the passivity of chromium which increases its resistance to chemical attack. While this is a desirable property for chromium as a final finish, it makes the surface extremely difficult to plate, as, for example, when gold decorative finishes are desired.
The state of the art until now precluded the direct plating of chromium and passive alloys, e.g., stainless 'stools with gold, in one step. Two or three steps were required depending on the process. One method involves stripping chromium anodically with caustic soda solution, activating the under layer of nickel plate exposed by removing the chromium with acid, followed by gold plating. A second process involves chromium stripping with 10-15% sulfuric acid. Both processes are extremely time consuming and difficult to execute as the plater has difficulty in discerning when the chromium has been entirely removed. Should residual chromium be left, there will be poor adhesion of the subsequent gold finish which will have a marred blotchy appearance. Stainless-steel parts, on the other hand, require a nickel or gold strike prior to gold plating, and there is difficulty in determining when there is a sufficient layer of nickel to suffice as a viable deposit.
The substrates chosen by the instant inventor were those used for gold plating automobile emblems, where the problem has been extant for many years, with either chromium-plated or stainless-steel emblems. After experimenting with various chemical compositions, the proper formulation was achieved which enabled the instantaneous plating of gold onto said chromium-plated substrates in one step. The resultant gold plate exhibited an excellent appearance, integrity of finish, outstanding adhesion and abrasion resistance. The preferred gold solution was a proprietary hard-acid gold solution introduced into the marketplace in 1993 called “Tivaglo-86” (trademark of Tivian Industries, Ltd.) for heavy gold plating up to 80 microinches. The gold solution is described in U.S. Pat. No. 5,575,900 of which the instant inventor is the co-inventor. The time of the multistage processes previously described is about an hour per automobile, while the instant invention's one-step process took several minutes. Furthermore, the multistage processes generated hazardous metal-bearing waste, especially with toxic chromium.
OBJECTS OF THE INVENTION
The main object of the invention is to plate gold in one step onto passive metal substrates, exemplary of which are chromium and stainless steel alloys, in such a manner as to yield a decorative gold finish with a variety of advantageous functional properties. Among the other objects of the invention are the individual functional properties.
Thus another object of the invention is to provide a gold finish with a rich 24-carat yellow color as differentiated from brassy-colored gold finishes.
Still another object of the invention is to provide for a gold finish exhibiting surface integrity and continuity with no visible imperfections.
Still another object of the invention is to provide a gold finish which will not detach from the passive chromium metal substrate surface and which exhibits superior adhesion.
Still another object of the invention is to achieve a gold finish which is sufficiently hard enough to meet the abrasion-resistance standards of those skilled in the art.
It should be realized that the aforementioned preceding four functional objectives of said invention should be achieved in one step on the aforesaid exemplary passive substrates.
The final object of the invention is to provide a method for gold plating passive chromium surfaces without generating hazardous wastes, especially toxic chromium.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds herein.
REFERENCES:
patent: 4046644 (1977-09-01), Liska
patent: 4168214 (1979-09-01), Fletcher et al.
patent: 4212708 (1980-07-01), Smagunova et al.
patent: 4606795 (1986-08-01), Ruiz et al.
patent: 5169514 (1992-12-01), Hendriks et al.
patent: 1082695 (1967-09-01), None
F. Lowenheim, “Electroplating”, McGraw-Hill, Inc. 19878, pp 266-268, 270 and 271.
Mayekar Kishor
Salter & Michaelson
Tivian Industries, Ltd.
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