CA1292154C - Multilayer coated corrosion resistant metal pipe - Google Patents
Multilayer coated corrosion resistant metal pipeInfo
- Publication number
- CA1292154C CA1292154C CA000568529A CA568529A CA1292154C CA 1292154 C CA1292154 C CA 1292154C CA 000568529 A CA000568529 A CA 000568529A CA 568529 A CA568529 A CA 568529A CA 1292154 C CA1292154 C CA 1292154C
- Authority
- CA
- Canada
- Prior art keywords
- film
- pipe
- corrosion resistant
- polyvinyl fluoride
- set forth
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 230000007797 corrosion Effects 0.000 title claims abstract description 28
- 238000005260 corrosion Methods 0.000 title claims abstract description 28
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 18
- 239000002184 metal Substances 0.000 title claims abstract description 18
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 claims abstract description 36
- 229920002620 polyvinyl fluoride Polymers 0.000 claims abstract description 23
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000011701 zinc Substances 0.000 claims abstract description 21
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 21
- 239000003822 epoxy resin Substances 0.000 claims abstract description 19
- 229920000647 polyepoxide Polymers 0.000 claims abstract description 19
- 229910000831 Steel Inorganic materials 0.000 claims description 22
- 239000010959 steel Substances 0.000 claims description 22
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 claims description 6
- 229910052802 copper Inorganic materials 0.000 claims description 6
- 239000010949 copper Substances 0.000 claims description 6
- 239000003792 electrolyte Substances 0.000 claims description 6
- 240000007817 Olea europaea Species 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 4
- PXKLMJQFEQBVLD-UHFFFAOYSA-N bisphenol F Chemical compound C1=CC(O)=CC=C1CC1=CC=C(O)C=C1 PXKLMJQFEQBVLD-UHFFFAOYSA-N 0.000 claims description 4
- FLKPEMZONWLCSK-UHFFFAOYSA-N diethyl phthalate Chemical compound CCOC(=O)C1=CC=CC=C1C(=O)OCC FLKPEMZONWLCSK-UHFFFAOYSA-N 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 229920003986 novolac Polymers 0.000 claims description 4
- 230000002378 acidificating effect Effects 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 3
- QTWJRLJHJPIABL-UHFFFAOYSA-N 2-methylphenol;3-methylphenol;4-methylphenol Chemical compound CC1=CC=C(O)C=C1.CC1=CC=CC(O)=C1.CC1=CC=CC=C1O QTWJRLJHJPIABL-UHFFFAOYSA-N 0.000 claims description 2
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims description 2
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- 229940106691 bisphenol a Drugs 0.000 claims description 2
- 238000009835 boiling Methods 0.000 claims description 2
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 claims description 2
- 229930003836 cresol Natural products 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims description 2
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 claims description 2
- 229920000151 polyglycol Polymers 0.000 claims description 2
- 239000010695 polyglycol Substances 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims description 2
- GTLDTDOJJJZVBW-UHFFFAOYSA-N zinc cyanide Chemical compound [Zn+2].N#[C-].N#[C-] GTLDTDOJJJZVBW-UHFFFAOYSA-N 0.000 claims description 2
- NIQCNGHVCWTJSM-UHFFFAOYSA-N Dimethyl phthalate Chemical compound COC(=O)C1=CC=CC=C1C(=O)OC NIQCNGHVCWTJSM-UHFFFAOYSA-N 0.000 claims 2
- FBSAITBEAPNWJG-UHFFFAOYSA-N dimethyl phthalate Natural products CC(=O)OC1=CC=CC=C1OC(C)=O FBSAITBEAPNWJG-UHFFFAOYSA-N 0.000 claims 1
- 229960001826 dimethylphthalate Drugs 0.000 claims 1
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 claims 1
- 239000000543 intermediate Substances 0.000 abstract description 18
- 239000000243 solution Substances 0.000 description 13
- 230000015572 biosynthetic process Effects 0.000 description 11
- 238000000034 method Methods 0.000 description 10
- 229920005989 resin Polymers 0.000 description 6
- 239000011347 resin Substances 0.000 description 6
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 3
- 238000004532 chromating Methods 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
- 229940091249 fluoride supplement Drugs 0.000 description 3
- 239000003973 paint Substances 0.000 description 3
- 238000007747 plating Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 238000005219 brazing Methods 0.000 description 2
- 150000001845 chromium compounds Chemical class 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 235000019253 formic acid Nutrition 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- 235000002639 sodium chloride Nutrition 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 229920002554 vinyl polymer Polymers 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- JWBZBIUNRGOCGQ-UHFFFAOYSA-N ethene;phthalic acid Chemical compound C=C.C=C.OC(=O)C1=CC=CC=C1C(O)=O JWBZBIUNRGOCGQ-UHFFFAOYSA-N 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- XUCNUKMRBVNAPB-UHFFFAOYSA-N fluoroethene Chemical compound FC=C XUCNUKMRBVNAPB-UHFFFAOYSA-N 0.000 description 1
- -1 formic acid Chemical class 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 239000006259 organic additive Substances 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 231100000167 toxic agent Toxicity 0.000 description 1
- 239000003440 toxic substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 description 1
- 229960001763 zinc sulfate Drugs 0.000 description 1
- 229910000368 zinc sulfate Inorganic materials 0.000 description 1
Landscapes
- Laminated Bodies (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A corrosion resistant metal pipe having an outer surface coated with a zinc film, a chromate film, an inter-mediate layer consisting substantially of an epoxy resin, and a polyvinyl fluoride film formed one upon another in the order listed.
A corrosion resistant metal pipe having an outer surface coated with a zinc film, a chromate film, an inter-mediate layer consisting substantially of an epoxy resin, and a polyvinyl fluoride film formed one upon another in the order listed.
Description
h MULTII~YEPc COATED CORROSION R~3SISTANT METAL PIPE
BACKGROUND OF THE INVEMTION
1. Field of the Invention:
This invention relates to a multilayer coated cor-rosion resistant metal pipe, or a metal pipe having an outer surface coated with a plurality of layers o corrosion resis-tant materials. It i5 ~icularly concerned with a metal pipe having a relatively small inside diameter not exceeding 20 mm.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a cross sectional view of a coated pipe embodying this invention;
FIGURE 2 is a cross sectional view of a coated pipe according to another embodiment of this invention; and FIGURE 3 is a cross sectional view of a known coated pipe.
BACKGROUND OF THE INVEMTION
1. Field of the Invention:
This invention relates to a multilayer coated cor-rosion resistant metal pipe, or a metal pipe having an outer surface coated with a plurality of layers o corrosion resis-tant materials. It i5 ~icularly concerned with a metal pipe having a relatively small inside diameter not exceeding 20 mm.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a cross sectional view of a coated pipe embodying this invention;
FIGURE 2 is a cross sectional view of a coated pipe according to another embodiment of this invention; and FIGURE 3 is a cross sectional view of a known coated pipe.
2. Descri~tion of the Prior Art:
1~ Metal pipes often have their outer surfaces covered with protective coating. These pipes are used for making, for example, pipelines for conveying a brake fluid and fuel in a motor vehicle. These pipelines are locat~d under the body of the vehicle. As they are used in such a bad environment, the pipes are required to have high degrees of corrosion resis-tance, scratch resistance, impact strength and mechanical wear resistance. Spiked tires have come to be often used in the cold season during which ice is likely to form on the road surfacs. These tires, however, damage the road surface and raise dust when it is not covered with ice. Rock salt is sprinkled onto the road surface to prevent its freezing. A
yearly increase in the use of rock salt, however, is making the problem of pipe corrosion more serious.
,.. ..
2~S~
The pipes are also liable to damage or wear by stones or mud spattered by the rotating wheels of the vehicle. It is, therefore, necessary that the pipes be so coated as to resist both chemical corrosion and mechanical damage or wear.
Reference is made to FIGURE 3 showing ~y way of example a known pipe of the type to which this invention pertains. It comprises a double-rolled steel pipe 11 made by rolling a steel strip or hoop twice and brazing its lon-gitudinal edges by means of a copper plating layer 12, or a seam welded steel pipe. The pipe 11 has an outer surface coated with an electroplated zinc film 13. The film 13 has an outer surface coated with a relatively thick special chromate film 14 having an olive color. The chromate Silm 14 has an outer surface coated with a fluorinated resin film 16. Pipes of this kind are disclosed in, for example, Japanese Patent Publications Nos. 60434jl982 and 23271/19~6.
The fluorinated resin film is formed by impregnat-ing the chromate film with a dispersion of polyvinyl fluo-ride immediately after the formation of the chromate film when it ls still in the state of a gel, and drying them under heat, so that~the fluorinated resin film may form an intimate bond with the chromate film. When the chromate film is formed by treating the pipe with a solution, it requires large amounts of a chromium compound and an organic acid, such as formic acid, used as a reducin~ a~ent. It 31.2~ L5~
is necessary to supply the treating solution with the chromium compound, etc. frequently and yet renew it at regular intervals of time in order to maintain a constant film forming capacity. The waste solution, however, con-tains a large amount of chro~ium having a valence of 6, which is a toxic substance, and its disposal, therefore, costs a great deal. Although the chromate film as formed is highly resistant to corrosion, the heat to which it is exposed during the formation of the resin film deprives it of water and thereb~ makes it brittle. The plastic defor-mation, such as bending or double flaring, of the pipe forms in the chromate film fine cracks which lower its rustproof-ing property.
SU~MARY O~? THE INVENTI ON
Under these circumstances, it is an object of this invention to provide a multi~ayer coated corrosion resistant metal pipe which can overcome the drawbacks of the prior art as hereinabove pointed out and is highly resistant to chemical corrosion, mechanical damage and wear.
This object is attained by a coated pipe which com-prises a metal pipe having an outer surface coated with a zinc film, a chromate film, an intermediate layer consisting substantially of an epoxy resin, and a polyvinyl fluoride film formed one upon another ln the order mentioned.
The coated pipe of this invention is particularly characterized in that the intermediate layer consistincJ
~2~
of an epoxy resin is pxesent between the chromate film and the polyvinyl fluoride fllm.
Other features and advantages of this invention will be apparent from the following description and the accompanying drawings.
DETAILED DESCRIPTION OF THE INV~;NTION
A multilayer coated pipe embodying this invention is sho~n in FIGURE 1. It comprises a metal pipe 1. More specifically, it is a double-rolled steel pipe formed by la rolling a steel hoop twice and brazing its longitudinal edges and other mutually contacting surfaces by means of a copper plating layer 2. The pipe has a relatively small inside diameter not exceeding 20 mm. A copper plating layer 2 is also provided on the outer surface of the pipe 1 ana has a thickness of, say, three microns.
The metal pipe 1 may alternatively be a seam welded steel pipe, or a seamless steel pipe made by drawing and having an appropriate diameter. Moreover, the pipe 1 does not necessarily need to ~e of steel, but may also be of A
~LZ9;~
other material, such as aluminum or copper. A modified form of pipe is shown by way of example in ~IGURE 2.
~ he outer surface of the metal pipe I is coated wi-th a zinc film 3. ~he zinc film 3 can be formed by a known electroplating method employing an acidic electrolyte containing sulfuric acid or an alkaline electrolyte contain-ing zinc cyanide. It has a thickness of ~ to 35 microns~
A zinc film having a thickness below five microns wou]d fail to provide satisfactory corrosion resistance, while a zinc film having a thickness over 35 microns would peel off the pipe when it is bent.
A chromate film 4 covers the zinc film 3. It is usually a film or chromate having a yellow color and is formed by using an ordinary solution containing chromic acid at a low concentration immediately after the formation of the zinc film 3. The film 4 may alternatively of chromate havlng an olive color if the pipe is of the type which will not be sub3ected to plastic deformation.
An intermediate layer 5 consisting substantially of an epoxy resin covers the chromate film 4, the epoxy resin of which being one member selected from bisphenol-A type epoxy resin, bisphenol-F type epoxy resin, bisphenol-AD type epoxy resin, phenol novolac based epoxy resin, cresol novolac based epo~y resin, brominated bisphenol-A -type epoxy resin and/or polyglycol epoxy resin and having a viscosity of 10 to 60 seconds (E`ord cup #4) at a temperature of 25 ~ 5C, ~9;~
being capable of baking at a temperature OI 2000 to 700C
for 10 to 25 seconds and having a hardness of formed film of B to 4H (pencil). ~he intermediate layer 5 is formed by dipping the chromate film 4 in the above-mentioned epoxy resin or spraying the epoxy resin onto t;he chromate film 4, and is dried under heat.
~he intermediate layer 5 has a thickness of 1 to 20 microns.
~Z~54 ~ layer having a thickness below one micron would fail to adhere to the chromate film 4, while a layer having a thick-ness over 20 microns would crack, or be separated from a polyvinyl fluoride film which will hereinafter be described in detail. The intermediate layer 5 having an appropriate thickness forms a strong bond with both the underlying chromate film 4 and the overlying resin film.
The polyvinyl fluoride film 6 covers the intermedi-ate layer 5. It is formed by employing a solution prepared by dispersing polyvinyl fluoride in a high-boiling solvent, such as dimethyl or diethylene phthalate, until no solid fluoride can be found. The intermediate layer is dipped in the solution, or the solution is sprayed onto the inter-mediate layer, and the solution covering the layer lS dried under heat at a temperature up to, say, 350C. The poly-vinyl fluoride film 6 has a thickness of 5 to 50 microns.
A polyvinyl fluoride film having a thickness below five microns would fail to provide satisfactory corrosion resist-ance, while a film having a thickness over 50 microns would not be more effective than any film having a thickness of 50 microns or below, but would only be more costly.
The films or layers 3 to 6 shown in FIGURE 2 are identical to their counterparts in FIGURE 1 which have hereinabove been described. No further description of the coated pipe shown in FIGURE 2 is, therefore, made.
The intermediate layer bonds -the chromate film and ~2~2~S4 the polyvinyl fluoride film so strongly that neither of these films may crack or peel away when the pipe is bent or otherwise deformed. The layer also adds to the corro-sion resistance of the pipe. The polyvinyl fluoride film S is a very good protective film because of its excellency in mechanical strength, and heat, weather and chemical resistances. The coated pipe of this invention is, there-fore, very suitable for use in a highly corrosive and abra-sive environment, such as under the bottom of a motor vehicle.
This invention is also valuable as it facilitates the control of the solution which is used to form the chromate film.
The invention will now be described more specifically with reference to a number of examples.
EXAMP~E 1 Five coated pipes were prepared in accordance with the following procedure:
(1~ Metal pipe:
Each pipe was a double-rolled steel pipe formed from a steel hoop coated with a copper layer having a thick-ness of three microns, and having an outside diameter of 4.76 mm and a wall thickness of 0.7 mm;
(2) Formation of a zinc film:
An electroplated zinc film having a thickness of 25 microns was formed on the outer surface of the steel pipe by employing an acidic electrolyte consisting mainly of zinc sulfate and containing an organic additive, and apply-~2~ 5~
ing an electric current at a density of 60 A/dm2 at a temperature of 55C to 60C;
1~ Metal pipes often have their outer surfaces covered with protective coating. These pipes are used for making, for example, pipelines for conveying a brake fluid and fuel in a motor vehicle. These pipelines are locat~d under the body of the vehicle. As they are used in such a bad environment, the pipes are required to have high degrees of corrosion resis-tance, scratch resistance, impact strength and mechanical wear resistance. Spiked tires have come to be often used in the cold season during which ice is likely to form on the road surfacs. These tires, however, damage the road surface and raise dust when it is not covered with ice. Rock salt is sprinkled onto the road surface to prevent its freezing. A
yearly increase in the use of rock salt, however, is making the problem of pipe corrosion more serious.
,.. ..
2~S~
The pipes are also liable to damage or wear by stones or mud spattered by the rotating wheels of the vehicle. It is, therefore, necessary that the pipes be so coated as to resist both chemical corrosion and mechanical damage or wear.
Reference is made to FIGURE 3 showing ~y way of example a known pipe of the type to which this invention pertains. It comprises a double-rolled steel pipe 11 made by rolling a steel strip or hoop twice and brazing its lon-gitudinal edges by means of a copper plating layer 12, or a seam welded steel pipe. The pipe 11 has an outer surface coated with an electroplated zinc film 13. The film 13 has an outer surface coated with a relatively thick special chromate film 14 having an olive color. The chromate Silm 14 has an outer surface coated with a fluorinated resin film 16. Pipes of this kind are disclosed in, for example, Japanese Patent Publications Nos. 60434jl982 and 23271/19~6.
The fluorinated resin film is formed by impregnat-ing the chromate film with a dispersion of polyvinyl fluo-ride immediately after the formation of the chromate film when it ls still in the state of a gel, and drying them under heat, so that~the fluorinated resin film may form an intimate bond with the chromate film. When the chromate film is formed by treating the pipe with a solution, it requires large amounts of a chromium compound and an organic acid, such as formic acid, used as a reducin~ a~ent. It 31.2~ L5~
is necessary to supply the treating solution with the chromium compound, etc. frequently and yet renew it at regular intervals of time in order to maintain a constant film forming capacity. The waste solution, however, con-tains a large amount of chro~ium having a valence of 6, which is a toxic substance, and its disposal, therefore, costs a great deal. Although the chromate film as formed is highly resistant to corrosion, the heat to which it is exposed during the formation of the resin film deprives it of water and thereb~ makes it brittle. The plastic defor-mation, such as bending or double flaring, of the pipe forms in the chromate film fine cracks which lower its rustproof-ing property.
SU~MARY O~? THE INVENTI ON
Under these circumstances, it is an object of this invention to provide a multi~ayer coated corrosion resistant metal pipe which can overcome the drawbacks of the prior art as hereinabove pointed out and is highly resistant to chemical corrosion, mechanical damage and wear.
This object is attained by a coated pipe which com-prises a metal pipe having an outer surface coated with a zinc film, a chromate film, an intermediate layer consisting substantially of an epoxy resin, and a polyvinyl fluoride film formed one upon another ln the order mentioned.
The coated pipe of this invention is particularly characterized in that the intermediate layer consistincJ
~2~
of an epoxy resin is pxesent between the chromate film and the polyvinyl fluoride fllm.
Other features and advantages of this invention will be apparent from the following description and the accompanying drawings.
DETAILED DESCRIPTION OF THE INV~;NTION
A multilayer coated pipe embodying this invention is sho~n in FIGURE 1. It comprises a metal pipe 1. More specifically, it is a double-rolled steel pipe formed by la rolling a steel hoop twice and brazing its longitudinal edges and other mutually contacting surfaces by means of a copper plating layer 2. The pipe has a relatively small inside diameter not exceeding 20 mm. A copper plating layer 2 is also provided on the outer surface of the pipe 1 ana has a thickness of, say, three microns.
The metal pipe 1 may alternatively be a seam welded steel pipe, or a seamless steel pipe made by drawing and having an appropriate diameter. Moreover, the pipe 1 does not necessarily need to ~e of steel, but may also be of A
~LZ9;~
other material, such as aluminum or copper. A modified form of pipe is shown by way of example in ~IGURE 2.
~ he outer surface of the metal pipe I is coated wi-th a zinc film 3. ~he zinc film 3 can be formed by a known electroplating method employing an acidic electrolyte containing sulfuric acid or an alkaline electrolyte contain-ing zinc cyanide. It has a thickness of ~ to 35 microns~
A zinc film having a thickness below five microns wou]d fail to provide satisfactory corrosion resistance, while a zinc film having a thickness over 35 microns would peel off the pipe when it is bent.
A chromate film 4 covers the zinc film 3. It is usually a film or chromate having a yellow color and is formed by using an ordinary solution containing chromic acid at a low concentration immediately after the formation of the zinc film 3. The film 4 may alternatively of chromate havlng an olive color if the pipe is of the type which will not be sub3ected to plastic deformation.
An intermediate layer 5 consisting substantially of an epoxy resin covers the chromate film 4, the epoxy resin of which being one member selected from bisphenol-A type epoxy resin, bisphenol-F type epoxy resin, bisphenol-AD type epoxy resin, phenol novolac based epoxy resin, cresol novolac based epo~y resin, brominated bisphenol-A -type epoxy resin and/or polyglycol epoxy resin and having a viscosity of 10 to 60 seconds (E`ord cup #4) at a temperature of 25 ~ 5C, ~9;~
being capable of baking at a temperature OI 2000 to 700C
for 10 to 25 seconds and having a hardness of formed film of B to 4H (pencil). ~he intermediate layer 5 is formed by dipping the chromate film 4 in the above-mentioned epoxy resin or spraying the epoxy resin onto t;he chromate film 4, and is dried under heat.
~he intermediate layer 5 has a thickness of 1 to 20 microns.
~Z~54 ~ layer having a thickness below one micron would fail to adhere to the chromate film 4, while a layer having a thick-ness over 20 microns would crack, or be separated from a polyvinyl fluoride film which will hereinafter be described in detail. The intermediate layer 5 having an appropriate thickness forms a strong bond with both the underlying chromate film 4 and the overlying resin film.
The polyvinyl fluoride film 6 covers the intermedi-ate layer 5. It is formed by employing a solution prepared by dispersing polyvinyl fluoride in a high-boiling solvent, such as dimethyl or diethylene phthalate, until no solid fluoride can be found. The intermediate layer is dipped in the solution, or the solution is sprayed onto the inter-mediate layer, and the solution covering the layer lS dried under heat at a temperature up to, say, 350C. The poly-vinyl fluoride film 6 has a thickness of 5 to 50 microns.
A polyvinyl fluoride film having a thickness below five microns would fail to provide satisfactory corrosion resist-ance, while a film having a thickness over 50 microns would not be more effective than any film having a thickness of 50 microns or below, but would only be more costly.
The films or layers 3 to 6 shown in FIGURE 2 are identical to their counterparts in FIGURE 1 which have hereinabove been described. No further description of the coated pipe shown in FIGURE 2 is, therefore, made.
The intermediate layer bonds -the chromate film and ~2~2~S4 the polyvinyl fluoride film so strongly that neither of these films may crack or peel away when the pipe is bent or otherwise deformed. The layer also adds to the corro-sion resistance of the pipe. The polyvinyl fluoride film S is a very good protective film because of its excellency in mechanical strength, and heat, weather and chemical resistances. The coated pipe of this invention is, there-fore, very suitable for use in a highly corrosive and abra-sive environment, such as under the bottom of a motor vehicle.
This invention is also valuable as it facilitates the control of the solution which is used to form the chromate film.
The invention will now be described more specifically with reference to a number of examples.
EXAMP~E 1 Five coated pipes were prepared in accordance with the following procedure:
(1~ Metal pipe:
Each pipe was a double-rolled steel pipe formed from a steel hoop coated with a copper layer having a thick-ness of three microns, and having an outside diameter of 4.76 mm and a wall thickness of 0.7 mm;
(2) Formation of a zinc film:
An electroplated zinc film having a thickness of 25 microns was formed on the outer surface of the steel pipe by employing an acidic electrolyte consisting mainly of zinc sulfate and containing an organic additive, and apply-~2~ 5~
ing an electric current at a density of 60 A/dm2 at a temperature of 55C to 60C;
(3) Formation of a chromate film~
A yellow chromate film was formed on the zinc film by employing a chromating solution containing chromium having a valence of 6 at as low a concentration as 1 g per liter;
A yellow chromate film was formed on the zinc film by employing a chromating solution containing chromium having a valence of 6 at as low a concentration as 1 g per liter;
(4) Formation of an intermediate layer:
The steel pipe was, then, dipped in a paint which had been prepared by dissolving an epoxy resin and a pigment in a solvent, and the paint on the pipe was heated at a temperature of 300C for 60 seconds, whereby an intermediate epoxy resin layer having a thickness of five microns was formed on the chromate film; and (5) Formation of a polyvinyl fluoride film:
Then, the pipe was dipped in a solution which had been prepared by dispersing polyvinyl fluoride in diethyl phthalate, and the soIution on the pipe was dried by heat-ing at a temperature of 350C for 60 seconds, whereby a polyvinyl~fluoride film having a thickness of 15 microns was formed on the intermediate layer.
Each coated pipe was tested for corrosion resistance.
A test specimen having a length of 300 mm was prepared from each coated pipe. A plurality of cuts spaced apart from one another by a distance of 10 mm were formed by a knife in the coating on each speclmen, so that -they might reach ~9~
the steel pipe. A salt solution spray test was conducted on the specimen in accordance with the method as specified by JIS Z2371. The salt solution caused a strlpe to appear along each cut as a result of the corrosion and discolora-tion of the chromate or zinc film. Time was counted until the stripes which had appeared along every two adjoining cuts and gradually spread eventually joined each other. The results are shown in a table below.
Five coated pipes were prepared in accordance with the following procedure:
(1) Metal pipe:
Each pipe was a seam welded steel pipe formed from the same steel hoop as that used in EXAMP~E 1, and having an outside diameter of 6.35 mm and a wall thickness of 0.7 mm;
(2) Formation of a zinc film:
The procedure of EXAMPLE 1 was repeated for forming an electroplated zinc film having a thickness of 25 microns on the outer surface of the steel pipe;
(3) Formation of a chromate film:
A yellow chromate film was formed on the æinc film by employing a chromating solution containing chromium hav-ing a valence of 6 at a concentration of 5 g per liter;
(4) Formation of an intermediate layer:
The same paint as that used in EXAMPLE 1 was sprayed _ g _ onto the chromate film, and was heated at a temperature of 320C for 60 seconds, whereby an intermediate epoxy resin layer having a thickness of five microns was formed on the chromate film; and (5) Formation of a polyvinyl fluoride film:
The same dispersion of polyvinyl fluoride as that used in EXAMPLE 1 was sprayed onto the intermediate layer, and was dried by heating at a temperature of 380C for 65 seconds, whereby a polyvinyl fluoride film having a thick-ness of 15 microns was formed on the intermediate layer and a coated pipe having a cross section as shown in FIGURE 2 was obtained.
The procedure of EXAMPLE 1 was repeated for conduct-ing a corrosion resistance test on each coated pipe. The results are shown in the table below.
COMPARATIVE EX~PLE
Five coated pipes were prepared in accordance with the following procedure:
(1) Metal pipe:
. 20 Each pipe was a double-rolled steel pipe duplicat-ing each pipe that had been used in EXAMPLE 1;
(2) Zinc film-The procedure of EXAMPLE 1 was repeated for forming an electroplated zinc film having a thickness of 25 microns on the outer surface of the steel pipe;
. (3) Chromate film:
, - 10 -~2~
The steep pipe was dipped for 20 seconds in a chromating solution containing chromium having a valence of 6 at a concentration of 13 g per liter and further containing formic acid and acetic acid, whereby a chromate film having an olive color was formed on the zinc film; and (4) Polyvinyl fluoride film:
The pipe which had been coated so far was washed with water and air was jetted against it to remove water from it. Then, the procedure of EXAMPLE 1 was repeated for forming a polyvinyl fluoride film on the chromate film.
The procedure of EXAMPLE l was repeated for conduct-ing a corrosion resistance test on each coated pipe. The results are shown in the table below.
TABLE
Time elapsed before merger of stripes along two adjoining knife cuts (hours) Specimen COMPARATIVE
No. EXAMPLE l EXAMPLE 2 EXAMPLE
2~ 2 1032 1104 600 3 1176 1224 57~
As is obvious from the table, the coated pipes embodying this invention were by far superior to the known coated pipe in corrosion resistance.
The steel pipe was, then, dipped in a paint which had been prepared by dissolving an epoxy resin and a pigment in a solvent, and the paint on the pipe was heated at a temperature of 300C for 60 seconds, whereby an intermediate epoxy resin layer having a thickness of five microns was formed on the chromate film; and (5) Formation of a polyvinyl fluoride film:
Then, the pipe was dipped in a solution which had been prepared by dispersing polyvinyl fluoride in diethyl phthalate, and the soIution on the pipe was dried by heat-ing at a temperature of 350C for 60 seconds, whereby a polyvinyl~fluoride film having a thickness of 15 microns was formed on the intermediate layer.
Each coated pipe was tested for corrosion resistance.
A test specimen having a length of 300 mm was prepared from each coated pipe. A plurality of cuts spaced apart from one another by a distance of 10 mm were formed by a knife in the coating on each speclmen, so that -they might reach ~9~
the steel pipe. A salt solution spray test was conducted on the specimen in accordance with the method as specified by JIS Z2371. The salt solution caused a strlpe to appear along each cut as a result of the corrosion and discolora-tion of the chromate or zinc film. Time was counted until the stripes which had appeared along every two adjoining cuts and gradually spread eventually joined each other. The results are shown in a table below.
Five coated pipes were prepared in accordance with the following procedure:
(1) Metal pipe:
Each pipe was a seam welded steel pipe formed from the same steel hoop as that used in EXAMP~E 1, and having an outside diameter of 6.35 mm and a wall thickness of 0.7 mm;
(2) Formation of a zinc film:
The procedure of EXAMPLE 1 was repeated for forming an electroplated zinc film having a thickness of 25 microns on the outer surface of the steel pipe;
(3) Formation of a chromate film:
A yellow chromate film was formed on the æinc film by employing a chromating solution containing chromium hav-ing a valence of 6 at a concentration of 5 g per liter;
(4) Formation of an intermediate layer:
The same paint as that used in EXAMPLE 1 was sprayed _ g _ onto the chromate film, and was heated at a temperature of 320C for 60 seconds, whereby an intermediate epoxy resin layer having a thickness of five microns was formed on the chromate film; and (5) Formation of a polyvinyl fluoride film:
The same dispersion of polyvinyl fluoride as that used in EXAMPLE 1 was sprayed onto the intermediate layer, and was dried by heating at a temperature of 380C for 65 seconds, whereby a polyvinyl fluoride film having a thick-ness of 15 microns was formed on the intermediate layer and a coated pipe having a cross section as shown in FIGURE 2 was obtained.
The procedure of EXAMPLE 1 was repeated for conduct-ing a corrosion resistance test on each coated pipe. The results are shown in the table below.
COMPARATIVE EX~PLE
Five coated pipes were prepared in accordance with the following procedure:
(1) Metal pipe:
. 20 Each pipe was a double-rolled steel pipe duplicat-ing each pipe that had been used in EXAMPLE 1;
(2) Zinc film-The procedure of EXAMPLE 1 was repeated for forming an electroplated zinc film having a thickness of 25 microns on the outer surface of the steel pipe;
. (3) Chromate film:
, - 10 -~2~
The steep pipe was dipped for 20 seconds in a chromating solution containing chromium having a valence of 6 at a concentration of 13 g per liter and further containing formic acid and acetic acid, whereby a chromate film having an olive color was formed on the zinc film; and (4) Polyvinyl fluoride film:
The pipe which had been coated so far was washed with water and air was jetted against it to remove water from it. Then, the procedure of EXAMPLE 1 was repeated for forming a polyvinyl fluoride film on the chromate film.
The procedure of EXAMPLE l was repeated for conduct-ing a corrosion resistance test on each coated pipe. The results are shown in the table below.
TABLE
Time elapsed before merger of stripes along two adjoining knife cuts (hours) Specimen COMPARATIVE
No. EXAMPLE l EXAMPLE 2 EXAMPLE
2~ 2 1032 1104 600 3 1176 1224 57~
As is obvious from the table, the coated pipes embodying this invention were by far superior to the known coated pipe in corrosion resistance.
Claims (9)
1. A corrosion resistant pipe comprising a metal pipe having an outer surface coated with a zinc film, a chromate film, an intermediate layer consisting substantially of an epoxy resin, and a polyvinyl fluoride film formed one upon another in the order listed.
2. A corrosion resistant pipe as set forth in claim 1, wherein said metal pipe is a steel pipe selected from among a double-rolled steel pipe, a seam welded steel pipe and a seamless steel pipe.
3. A corrosion resistant pipe as set forth in claim 1, wherein said metal pipe is of a material selected from among aluminum and copper.
4. A corrosion resistant pipe as set forth in claim 1, wherein said zinc film is an electroplated film formed by employing an electrolyte selected from among an acidic electrolyte containing sulfuric acid and an alkaline electrolyte containing zinc cyanide.
5. A corrosion resistant pipe as set forth in claim 4, wherein said chromate film is of a material selected from among yellow chromate formed from a solution having a low concentration of chromic acid and a chromate having an olive color.
6. A corrosion resistant pipe as set forth in claim 1, wherein the epoxy resin is at least one member selected from a group consisting of bisphenol-A type, bisphenol-F type, bisphenol-AD type, phenol novolac based, cresol novolac based, brominated bisphenol-A type and polyglycol epoxy resins.
7. A corrosion resistant pipe as set forth in claim 6, wherein said polyvinyl fluoride film is one formed by con-tacting said intermediate layer with a solution of polyvinyl fluoride and drying and solution under heat.
8. A corrosion resistant pipe as set forth in claim 7, wherein said solution of polyvinyl fluoride is one prepared by dispersing said polyvinyl fluoride in a high-boiling solvent selected from among dimethyl phthalate and diethyl phthalate and is free from any solid polyvinyl fluoride.
9. A corrosion resistant pipe as set forth in claim 1 wherein said zinc film has a thickness of 5 to 35 microns, said intermediate layer has a thickness of 1 to 20 microns, and said polyvinyl fluoride film has a thickness of 5 to 50 microns.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000568529A CA1292154C (en) | 1988-06-03 | 1988-06-03 | Multilayer coated corrosion resistant metal pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000568529A CA1292154C (en) | 1988-06-03 | 1988-06-03 | Multilayer coated corrosion resistant metal pipe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1292154C true CA1292154C (en) | 1991-11-19 |
Family
ID=4138132
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000568529A Expired - Lifetime CA1292154C (en) | 1988-06-03 | 1988-06-03 | Multilayer coated corrosion resistant metal pipe |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1292154C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012113862A2 (en) | 2011-02-24 | 2012-08-30 | Uponor Innovation Ab | Making pipe for liquid conveyance |
| EP2677221A1 (en) | 2012-06-18 | 2013-12-25 | Uponor Innovation AB | Multilayer composite pipe and pipe connection |
| NO20161954A1 (en) * | 2016-12-09 | 2018-06-11 | Nexans | Remote detection of insulation damage on insulated tubes or pipes |
-
1988
- 1988-06-03 CA CA000568529A patent/CA1292154C/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012113862A2 (en) | 2011-02-24 | 2012-08-30 | Uponor Innovation Ab | Making pipe for liquid conveyance |
| EP2677221A1 (en) | 2012-06-18 | 2013-12-25 | Uponor Innovation AB | Multilayer composite pipe and pipe connection |
| WO2013189874A1 (en) | 2012-06-18 | 2013-12-27 | Uponor Innovation Ab | Multilayer composite pipe and pipe connection |
| NO20161954A1 (en) * | 2016-12-09 | 2018-06-11 | Nexans | Remote detection of insulation damage on insulated tubes or pipes |
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