Pipes and tubular conduits – Distinct layers – Coated
Reexamination Certificate
1999-07-26
2001-12-04
Hook, James (Department: 3752)
Pipes and tubular conduits
Distinct layers
Coated
C138S142000, C138S143000, C138S171000
Reexamination Certificate
active
06325107
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a metal pipeline having a protective coating layer for an automobile, which is excellent in heat resistance, corrosion resistance and impact resistance and used for transportation of fluids such as oils and fuels under severe corrosive circumstances.
2. Description of Prior Arts
For preventing damage to brake oil or fuel oil pipelines of an automobile disposed under the floor of a car body caused by popping pebbles or splashing mud, preventing damage caused by interference between pipelines and other parts in an engine room, or preventing damage caused by interference between tools or parts upon assembling parts, a coated pipe has been known which is manufactured by forming a zinc plating layer on the outer surface of a steel pipe, forming a chromate layer on the zinc plating layer and covering the chromate layer with an extruded thermoplastic resin such as nylon, polyethylene or polypropylene resin.
However, since the resin is extruded by using an extrusion molding machine upon coating an extruded thermoplastic resin, such a coated pipe suffers from a problem that hydrates contained in the chromate layer are evaporated by heating upon molding and the chromate layer shrinks to cause cracking in the layer, so that corrosion resistance is deteriorated remarkably, particularly, to a portion in which a substrate is exposed due to injury of the resin by the popping stones or like, to a portion in which the resin is peeled off for the fabrication of a pipe end or to a portion in which the resin is not covered during intermittent extrusion molding.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a metal pipeline for use in an automobile, which has durability under severe corrosive circumstances including mechanical external forces and is excellent in heat resistance, corrosion resistance and impact resistance.
The present inventor has made earnest studies for overcoming the problem and attaining the foregoing object and, as a result, has accomplished the present invention based on the finding that degradation of the corrosion resistance caused by heating upon extrusion molding of resin coating is reduced, as compared with pipelines of the prior art having a yellow chromate layer applied on the zinc plating layer, by forming a zinc-nickel alloy plating layer on the outer circumferential surface of a metal tube, forming a colorless, yellow, bronze or black chromate layer thereover and, further, forming a nickel plating layer as an underlayer of the zinc-nickel alloy plating layer.
That is, in accordance with a first aspect of the present invention, there is provided a metal pipeline having a protective coating layer for use in an automobile comprising a metal tube, a zinc-nickel alloy plating layer formed on the outer circumferential surface of the metal tube, a chromate layer formed on the zinc-nickel alloy plating layer and an extrusion molded thermoplastic resin coating layer formed on the chromate layer.
Further, in accordance with a second aspect of the present invention, there is provided a metal pipeline having a protective coating layer for use in an automobile comprising a metal tube, a nickel plating layer formed on the outer circumferential surface of the metal tube, a zinc-nickel alloy plating layer formed on the nickel plating layer, a chromate layer formed on the zinc-nickel alloy plating layer and an extrusion molded thermoplastic resin coating layer formed on the chromate layer.
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Arent Fox Kintner & Plotkin & Kahn, PLLC
Hook James
Usui Kokusai Sangyo Kaisha Limited
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