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EP-4198362-B1 - ABRASION RESISTANT COATED TUBE

EP4198362B1EP 4198362 B1EP4198362 B1EP 4198362B1EP-4198362-B1

Inventors

  • CARDWELL, BRIAN J.
  • BREUER, THOMAS

Dates

Publication Date
20260506
Application Date
20221214

Claims (9)

  1. A coated metal pipe (10) for use as an automotive fluid transport tube comprising: a single or double walled tubing (12) formed into a circular cross-sectional profile; at least one intermediate layer primer layer (18) applied over said tubing: and an outer layer comprising a polyamide (20) incorporating an immiscible additive, wherein the immiscible additive is selected from Ultra High Molecular Weight (UHMW) silicones, UHMW polyethylene (UHMW-PE), and mixtures thereof.
  2. The coated metal pipe (10) of claim 1, wherein said tubing comprises steel.
  3. The coated metal pipe (10) of claim 1 or claim 2, said tubing further comprising any of a copper plated low carbon steel, low carbon steel, stainless steel, or aluminum.
  4. The coated metal pipe (10) of any of claims 1 to 3, further comprising a nickel plating applied to an inner diameter of said tubing.
  5. The coated metal pipe (10) of any of claims 1 to 4, said intermediate layer (16) further comprising a corrosion inhibiting zinc/aluminum alloy or a corrosion inhibiting magnesium alloy further comprising one or more of aluminum, zinc, manganese, silicon, copper, rare earth metals or zirconium.
  6. The coated metal pipe of any of claims 1 to 5, further comprising said intermediate layer (16) being selected from a group consisting of a chrome free conversion coating, primer or primer/adhesive coating, or passivation coating copper coating.
  7. A method for manufacturing a coated metal pipe (10) for use as an automotive fluid transport tube, comprising the steps of: forming a copper plated carbon steel (12) into a tubing exhibiting a circular cross-sectional profile; forming at least one intermediate primer layer (18) including a corrosion inhibiting zinc/aluminum alloy applied over the tubing; forming an outer polyamide layer (20) applied over the intermediate layer (18), the outer layer compounded with an immiscible additive at 1-15% by weight; and wherein the immiscible additive is selected from Ultra High Molecular Weight (UHMW) silicones, UHMW polyethylene (UHMW-PE), and mixtures thereof.
  8. The method as described in claim 7, further comprising the step of applying a nickel plating to an inner diameter of the tubing.
  9. The method as described in claim 7 or claim 8, further comprising the step of the intermediate layer (14, 16, 18) being selected from a group consisting of a chrome free conversion coating (16), primer or primer/adhesive coating (18), or passivation coating (14) copper coating or a corrosion inhibiting magnesium alloy further comprising one or more of aluminum, zinc, manganese, silicon, copper, rare earth metals or zirconium.

Description

This application claims priority to provisional application 63/289847 filed December 15, 2021. The present invention relates to a metal tube for vehicle piping and more specifically relates to a coated metal tube which is abrasion resistant. The tubes have a central steel tube that includes an outermost coating of a polyamide material incorporating a non-conductive additive to reduce the friction coefficient of the polyamide material. BACKGROUND Metallic tubes are typically coated with sacrificial metallic layers to protect the base steel tube against corrosion. A protective barrier layer of a non-metallic thermoplastic has been typically applied over the base steel tube. The thermoplastic may be in the form of a chemically resistant long-chain polyamide 12 or 6,12 thermoplastic or similar thermoplastic coating that is designed to be an unbroken layer to keep corrosive electrolytes from coming into direct contact with the metallic substrate under the thermoplastic coating. In order to maintain the protection from this layer, the polyamide layer itself must be resistant to chemicals (such as crack-inducing chloride salts), impact damage (stone pecking or chipping) as well as resistant to wear and abrasion from other objects contacting the surface. Current products add additional layers to the outer part of the tube (such as polypropylene) but this adds additional manufacturing steps and makes the diameter of the tubing (and the clips that hold the tubing) larger. It is therefore desirable to achieve increased performance from the existing polyamide layer without adding too much cost and not changing the basic application method for the polyamide layer. Polyamide coatings are generally known to exhibit high wear resistant properties along and provide a liquid water barrier to the underlying metallic corrosion protective coatings. Coating thicknesses on steel tubes can vary significantly but application thicknesses in the area of 100 micrometers to 1 mm are not uncommon. Such coatings can further include either or both thermoset and thermoplastic compositions and are often used for finishing and protection of metal surfaces. The prior art is documented with examples of automotive fluid tubing utilizing such coatings to provide varying performance characteristics. A first example of this is shown by the automotive fluid tubing of Picco et al., U.S. Pat. No. 6,915,820 which is configured for carrying any of gasoline/diesel fuel or hydraulic fluid and is composed of a metal with a coating of aluminum, over which is extrusion coated a polyamide 12 layer for improving the wear-resistance and corrosion-resistance of the tubing. A further example of the prior art is found in Berger et al., U.S. Pat. No. 9,556,358 which teaches a method for coating of a metallic article, in which the metal surface is coated with a polymer or a two-component system that reacts to form a polymer following application to the metal surface. The composition includes a 70-2700 meq/kg olefinic double bonds which leads to stronger adhesion and to increased corrosion resistance. US 2018/0119871, EP3219485, to Kawai, teaches a coated metal pipe in which the multilayered coating includes a chemical conversion layer and a primer layer which further includes a polyamide imide and at least one kind of additive component selected from a polyamide, a fluorine resin, a silane coupling agent, and an epoxy resin. Another composition that has been proposed involves the addition of graphene additives to the polyamide to improve performance. However, this creates an electrically conductive coating which may not be optimal for resistance for stray current corrosion. SUMMARY The present invention is defined in the appended claims and discloses a coated metal pipe for use as an automotive fluid transport tube including any of a single or double walled tubing formed into a circular cross sectional profile. At least one intermediate primer layer is applied over the tubing. A polyamide incorporating an additive is further applied over the intermediate layer. The additives may include ultra high molecular weight silicones, ultrahigh molecular weight polyethylene, polytetrafluorethylene or mixtures of two or more of these additives. Additional features include the polyamide layer further including any of a PA 6/12 or PA 12 sacrificial outer layer. The tubing may also include any of a copper plated low carbon steel, low carbon steel, stainless steel, or aluminum. A nickel plating can be applied to an inner diameter of the tubing. The intermediate diameter may also include a corrosion inhibiting zinc/aluminum alloy or other corrosion inhibiting material. The intermediate layer can further include a chrome free conversion coating, primer or primer/adhesive coating, or passivation coating copper coating or other suitable coating. In an embodiment is provided a coated metal pipe for use as an automotive fluid transport tube comprising a single or double walled tubing f