Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2002-01-23
2004-06-15
La Villa, Michael (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S659000, C428S457000, C428S469000, C205S220000, C205S306000, C427S406000, C427S419100
Reexamination Certificate
active
06749953
ABSTRACT:
FILED OF THE INVENTION
The present invention concerns a zinc whiskerless galvanized product having multi-layer rust prevention film having an excellent rust prevention, self-repair ability, and coating adhesion, a composition for forming multi-layer rust prevention film, and a manufacturing method of a zinc whiskerless galvanized product having multi-layer rust prevention film using the same.
BACKGROUND ART
Since electric and electronic components such as cover, case, chassis or other body of various components in a large electronics domain including computer equipment, communication equipment or the like require a high corrosion resistance, solderbility and electric properties, galvanization is recommended for these components, because it is strongly rust prevention in respect to the base material such as iron products, extremely excellent in corrosion resistance and cheap.
However, the galvanization has a problem that whiskers tend to be produced with time near the room temperature. The generation of zinc whisker short-circuits with counterpart components in a circuit or between terminals, provokes noise or deficient insulation, causes short-circuit troubles of electro-electronic components or the others, and more particularly, the zinc whisker generation increases short-circuit troubles along with the retrenchment of interval between components as electro-electronic components or the others are becoming smaller, high density, more complex, and low power.
The Inventors have examined diligently these problems and already proposed a lustrous galvanized product preventing completely the generation of zinc whisker for electro-electronic components and a lustrous galvanization method (Japan Patent Publication Laid-Open No. HEI 9-3684, Specifications of Japan Patent Application No. HEI 11-148183, “Hyomen Gijutsu Vol 49, No. 5 (1998), “Hyomen Gijutsu” Vol. 51, No. 7 (2000)9. The galvanized product presented problems of bad effects to human body and environmental pollution, as because it is surface-treated with chromate including sexivalent chrome for the purpose of surface protection or rust prevention.
On the other hand, the Inventors have already proposed a method for forming on a metal substrate a film presenting excellent rust prevention and self repair ability (Specification of Japan Patent Application No. HEI 11-272272) without using a treatment liquid containing sexivalent chrome; however, the formation of a coating by a further application of coating on a already formed film had a problem that the coating becomes less adhesive and peals off for some composition of rust prevention film.
DISCLOSURE OF THE INVENTION
The present invention has a first object of providing a galvanized product, wherein a galvanized film preventing completely the generation of zinc whisker on the surface of a metal substrate, and a multi-layer rust prevention film presenting not only rust prevention and self repair ability as excellent as the case of sexivalent chrome, but also an excellent coating adhesion, are formed on the surface of the galvanized film, without using chemicals such as injurious sexivalent chrome affecting the environment.
The present invention has a second object of providing a composition for multi-layer rust prevention film formation to obtain the composition for multi-layer rust prevention film easily.
Further, the present invention has a third object of providing a method for manufacturing easily the galvanized product of the present invention.
The Inventors have studied diligently in order to resolve problems of the related art, resulting in finding that the generation of zinc whisker can be prevent completely by the synergistic of galvanized film and multi-layer rust prevention films and, at the same time, a galvanized product excellent in rust prevention, self repair ability, and coating adhesion can be obtained by steps of forming closely a galvanized product wherein the generation of zinc whisker is prevented completely by galvanizing the surface of a metal substrate with a specific bath composition, thereafter, first of all, forming closely a first rust prevention film mainly containing tannic acid on the galvanized film, then forming closely a second rust prevention film containing mainly metal ions or the others on the upper portion of the first rust prevention film, and further, forming closely a third rust prevention film mainly containing tannic acid on the second rust prevention film, for leading to achieve the present invention.
In short, the present invention concerns a whiskerless galvanized product having a multi-layer rust prevention film, comprising a galvanized film formed closely on the surface of a metal substrate, presenting a lattice distortion of 0.02 to 0.35% of plated film measure by an X-ray diffractometer and carbon content of 0.01 to 0.07 mass % in plated film, a first rust prevention film mainly containing tannic acid formed closely on the galvanized film, a second rust prevention film containing mainly metal ions and/or metal compounds formed on the upper portion of the first rust prevention film, and a third rust prevention film mainly containing tannic acid on the second rust prevention film.
The present invention still further concerns the galvanized product described above, plated on the metal surface using a zinc cyanide bath whose caustic soda concentration is 50 to 160 g/L, zinc concentration is 10 to 30 g/L, a ratio of sodium cyanide concentration (g/L) to zinc concentration (g/L) to more than 3 and equal or inferior to 4, and to which a brightener is added.
The present invention still further concerns the galvanized product described above, wherein the metal substrate has a metal surface selected from a group comprising iron base material, or zinc, nickel, aluminum, magnesium, copper or alloys of two or more metals selected from these metals.
The present invention still further concerns the galvanized product described above, wherein the metal ion is a mixture of one or two species or more selected from Mo, V, Ti, W, Zr, while the metal compound is a mixture of one or two kinds or more of metal compounds containing these metals.
The present invention also concerns composition for multi-layer rust prevention film formation composed of a first treatment liquid containing tannic acid for forming the first rust prevention film and the third rust prevention film, and a second treatment liquid containing metal ions and/or metal compounds for forming the second rust prevention film.
The present invention further concerns composition for multi-layer rust prevention film formation described above, wherein the tannic acid concentration of the first treatment liquid is in a range of 0.1 to 30 g/L and pH is in a range of 3.5 to 8.0.
The present invention still further concerns the composition for multi-layer rust prevention film formation described above, wherein pH of the second treatment liquid is in a range of 2.0 to 10.0.
The present invention additionally concerns a manufacturing method of the galvanized product described above, comprising the following steps:
forming closely a galvanized film presenting a lattice distortion of 0.02 to 0.35% of plating film measured by an X-ray diffractometer and a carbon content of 0.01 to 0.07 mass % in plated film, by plating on the surface of a metal substrate using a zinc cyanide bath whose caustic soda concentration is 50 to 160 g/L, zinc concentration is 10 to 30 g/L, a ratio of sodium cyanide concentration (g/L) to zinc concentration (g/L) is more than 3 and equal or inferior to 4, and to which a brightener is added, and thereafter washing with water;
next, forming a first rust prevention film mainly containing tannic acid closely on the galvanized film by treating the galvanized film with a first treatment liquid containing tannic acid, and thereafter washing with water;
continuously, forming a second rust prevention film containing mainly metal ions and/or metal compounds on the upper portion of the first rust prevention film by treating with a second treatment liquid containing metal ions and/or
Katano Takazumi
Mizuno Eiki
Muroi Ryouichi
Sawatari Akira
La Villa Michael
Sambix Corporation
Weingarten Schurgin, Gagnebin & Lebovici LLP
LandOfFree
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