JP3759312B2 - Anticorrosion coating method for galvanized steel - Google Patents
Anticorrosion coating method for galvanized steel Download PDFInfo
- Publication number
- JP3759312B2 JP3759312B2 JP11270798A JP11270798A JP3759312B2 JP 3759312 B2 JP3759312 B2 JP 3759312B2 JP 11270798 A JP11270798 A JP 11270798A JP 11270798 A JP11270798 A JP 11270798A JP 3759312 B2 JP3759312 B2 JP 3759312B2
- Authority
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- Prior art keywords
- galvanized steel
- resin
- steel material
- coating
- weight
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- 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 - Fee Related
Links
- 238000000576 coating method Methods 0.000 title claims description 135
- 229910001335 Galvanized steel Inorganic materials 0.000 title claims description 85
- 239000008397 galvanized steel Substances 0.000 title claims description 85
- 239000011248 coating agent Substances 0.000 claims description 104
- 239000000463 material Substances 0.000 claims description 63
- 229920005989 resin Polymers 0.000 claims description 62
- 239000011347 resin Substances 0.000 claims description 62
- 239000000843 powder Substances 0.000 claims description 55
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 claims description 45
- 229910000165 zinc phosphate Inorganic materials 0.000 claims description 45
- 229920013716 polyethylene resin Polymers 0.000 claims description 30
- 229920005672 polyolefin resin Polymers 0.000 claims description 30
- -1 polypropylene Polymers 0.000 claims description 26
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- 238000000034 method Methods 0.000 claims description 21
- 238000005260 corrosion Methods 0.000 claims description 20
- 229910000831 Steel Inorganic materials 0.000 claims description 16
- 239000010959 steel Substances 0.000 claims description 16
- 239000000155 melt Substances 0.000 claims description 15
- 229920006242 ethylene acrylic acid copolymer Polymers 0.000 claims description 13
- 229920005648 ethylene methacrylic acid copolymer Polymers 0.000 claims description 13
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 11
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 11
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 claims description 11
- 150000008064 anhydrides Chemical class 0.000 claims description 8
- 238000012986 modification Methods 0.000 claims description 5
- 230000004048 modification Effects 0.000 claims description 5
- 230000037452 priming Effects 0.000 claims description 2
- 150000001735 carboxylic acids Chemical class 0.000 claims 2
- 238000004925 denaturation Methods 0.000 claims 2
- 230000036425 denaturation Effects 0.000 claims 2
- 238000010422 painting Methods 0.000 claims 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims 1
- 239000011701 zinc Substances 0.000 claims 1
- 229910052725 zinc Inorganic materials 0.000 claims 1
- 239000002987 primer (paints) Substances 0.000 description 35
- 230000007797 corrosion Effects 0.000 description 15
- 239000003795 chemical substances by application Substances 0.000 description 12
- 238000012360 testing method Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 238000004381 surface treatment Methods 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 239000000853 adhesive Substances 0.000 description 6
- 230000001070 adhesive effect Effects 0.000 description 6
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 6
- 239000012530 fluid Substances 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- VZCYOOQTPOCHFL-OWOJBTEDSA-N Fumaric acid Chemical compound OC(=O)\C=C\C(O)=O VZCYOOQTPOCHFL-OWOJBTEDSA-N 0.000 description 4
- 238000005246 galvanizing Methods 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 230000001771 impaired effect Effects 0.000 description 4
- 230000000704 physical effect Effects 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000007654 immersion Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000008188 pellet Substances 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 230000008961 swelling Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 description 2
- OFNISBHGPNMTMS-UHFFFAOYSA-N 3-methylideneoxolane-2,5-dione Chemical compound C=C1CC(=O)OC1=O OFNISBHGPNMTMS-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 2
- 238000003916 acid precipitation Methods 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 239000008119 colloidal silica Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 229920001971 elastomer Polymers 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 239000001530 fumaric acid Substances 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 2
- 239000011976 maleic acid Substances 0.000 description 2
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000007769 metal material Substances 0.000 description 2
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
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- 239000007921 spray Substances 0.000 description 2
- ONDPHDOFVYQSGI-UHFFFAOYSA-N zinc nitrate Chemical compound [Zn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ONDPHDOFVYQSGI-UHFFFAOYSA-N 0.000 description 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229920006026 co-polymeric resin Polymers 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000007610 electrostatic coating method Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000005038 ethylene vinyl acetate Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 239000012760 heat stabilizer Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 description 1
- 229920001225 polyester resin Polymers 0.000 description 1
- 239000004645 polyester resin Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000002516 radical scavenger Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000007751 thermal spraying Methods 0.000 description 1
- 239000006097 ultraviolet radiation absorber Substances 0.000 description 1
- MFXMOUUKFMDYLM-UHFFFAOYSA-L zinc;dihydrogen phosphate Chemical compound [Zn+2].OP(O)([O-])=O.OP(O)([O-])=O MFXMOUUKFMDYLM-UHFFFAOYSA-L 0.000 description 1
- 150000007934 α,β-unsaturated carboxylic acids Chemical class 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
- C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
- C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
- C23C28/3225—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only with at least one zinc-based layer
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/26—After-treatment
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
- C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
- C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
Description
【０００１】
【発明が属する技術分野】
本発明は、防食塗装方法、特に、亜鉛メッキ鋼材に防食性を付与するための防食塗装方法に関する。
【０００２】
【従来の技術とその課題】
橋梁、送電線鉄塔、電車の架線用支柱、通信ケーブル用支柱等を構築するために用いられる鋼材は、防食性を高めるために、表面に亜鉛メッキが付与される場合が多い。このような亜鉛メッキが付与された鋼材は、通常の大気中では良好な耐食性を発揮し得る。しかしながら、亜鉛メッキは、塩水に曝され易い海浜付近の環境や酸性雨を受け易い環境等の腐食性環境下においてはメッキ層が数年で消失してしまう場合が多く、このような腐食性環境下では鋼材に対して耐久性のある防食性を付与するのが困難である。
【０００３】
このため、亜鉛メッキされた鋼材の防食性を高めるために、その表面に粉体樹脂塗装を施す試みがなされている。例えば、特開昭６０−１４３９５２号公報には、亜鉛メッキした鉄製部材の表面にエチレンとα，β−不飽和カルボン酸との共重合体樹脂粉末を用いて粉体塗装した土木建築用樹脂被覆鉄部材が開示されている。ところが、このような土木建築用樹脂被覆鉄部材は、粉体塗装により形成した塗膜の接着性が十分ではないため、上述のような腐食性環境下において塗膜の剥離や亜鉛メッキの脆化が生じ易く、防食性がやはり長期間安定に維持されにくい。
【０００４】
また、鋼材に亜鉛メッキを施す際の余熱を利用して、亜鉛メッキ層上に飽和ポリエステル樹脂系の粉体塗料を適用する試みがなされている。この場合は、接着性が比較的良好な塗膜を亜鉛メッキ層上に付与することができるので、腐食環境下における亜鉛メッキ鋼材の防食性は比較的安定に長期間維持されるが、粉体塗料を適用できるのが鋼材に対して亜鉛メッキを施すことができる時と場所に限られる。このため、このような防食塗装方法は、汎用性に乏しく実用性を欠く（例えば、防錆管理，（５）１〜１２，１９９７参照）。
【０００５】
本発明の目的は、亜鉛メッキ鋼材に対し、腐食性環境下でも長期間に渡って安定な防食性を付与することができ、しかも実用的な防食塗装方法を実現することにある。
【０００６】
【課題を解決するための手段】
本発明者等は、上述の課題を解決すべく鋭意検討した結果、亜鉛メッキ鋼材の表面にリン酸亜鉛処理を施し、必要に応じてさらにプライマー処理を施した後にポリオレフィン系樹脂粉体塗料による塗膜を付与すると、接着性および腐食性環境下における耐久性の良好な樹脂被膜が亜鉛メッキ鋼材に対して付与されることを見出し、本発明を完成した。
【０００７】
すなわち、本発明の防食塗装方法は、亜鉛メッキ鋼材に防食性を付与するためのものであり、亜鉛メッキ鋼材の表面をリン酸亜鉛処理する工程と、リン酸亜鉛処理された亜鉛メッキ鋼材の表面にポリオレフィン系樹脂粉体塗料による塗膜を付与する工程とを含んでいる。なお、この防食塗装方法は、ポリオレフィン系樹脂粉体塗料による塗膜を付与する前に、リン酸亜鉛処理された亜鉛メッキ鋼材の表面をプライマー処理する工程をさらに含んでいてもよい。
【０００８】
ここで用いられるポリオレフィン系樹脂粉体塗料は、例えば、エチレン−アクリル酸共重合体樹脂５０〜１００重量％とポリエチレン樹脂０〜５０重量％とを含むものである。この場合、エチレン−アクリル酸共重合体樹脂としては、通常、アクリル酸の割合が１〜２０重量％であり、かつ１９０℃におけるメルトフローレートが５〜５０ｇ／１０分のものが用いられる。
【０００９】
また、本発明の他の形態で用いられるポリオレフィン系樹脂粉体塗料は、例えば、エチレン−メタクリル酸共重合体樹脂５０〜１００重量％とポリエチレン樹脂０〜５０重量％とを含むものである。この場合、エチレン−メタクリル酸共重合体樹脂としては、通常、メタクリル酸の割合が５〜２０重量％であり、かつ１９０℃におけるメルトフローレートが３〜５０ｇ／１０分のものが用いられる。
【００１０】
本発明のさらに他の形態で用いられるポリオレフィン系樹脂粉体塗料は、例えば、変性ポリエチレン樹脂５０〜１００重量％とポリエチレン樹脂０〜５０重量％とを含むものである。この場合、変性ポリエチレン樹脂としては、通常、ポリエチレン樹脂を不飽和カルボン酸およびその無水物のうちの１つによりグラフト変性したものが用いられる。
【００１１】
なお、上述の各形態で用いられるポリエチレン樹脂は、通常、１９０℃におけるメルトフローレートが１〜８０ｇ／１０分であり、かつ密度が０．９１〜０．９４ｇ／ｃｍ3のものである。
【００１２】
本発明のさらに他の形態で用いられるポリオレフィン系樹脂粉体塗料は、例えば、変性ポリプロピレン樹脂５０〜１００重量％とポリプロピレン樹脂０〜５０重量％とを含むものである。この場合、変性ポリプロピレン樹脂としては、通常、ポリプロピレン樹脂を不飽和カルボン酸およびその無水物のうちの１つによりグラフト変性したものが用いられる。なお、ここで用いられるポリプロピレン樹脂は、通常、２３０℃におけるメルトフローレートが１〜１００ｇ／１０分のものである。
【００１３】
本発明の防食塗装方法において、リン酸亜鉛処理およびプライマー処理自体は公知の防錆方法である。しかし、本発明において、リン酸亜鉛処理やプライマー処理により形成される被膜は、表面に露出することなく下地剤として用いられ、そのアンカー効果によりポリオレフィン系樹脂塗膜を亜鉛メッキ鋼材に対して強固に接着する。亜鉛メッキ鋼材に対してリン酸亜鉛処理等を予め施した場合にポリオレフィン系樹脂塗膜の接着性および耐久性が向上する機構はつまびらかではないが、亜鉛メッキ表面とリン酸亜鉛処理により形成される被膜との間の強い接着力、リン酸亜鉛処理による被膜とポリオレフィン系樹脂塗膜との良好な付着性、リン酸亜鉛処理により形成される被膜とプライマー処理により形成される被膜との間の良好な接着性およびプライマー処理により形成される被膜とポリオレフィン系樹脂塗膜に含まれる極性基との相互作用による強固な接着性などが相乗的に作用して優れたアンカー効果を発揮しているものと推察される。
【００１４】
なお、本発明において、リン酸亜鉛処理後の亜鉛メッキ鋼材に対してさらにプライマー処理を施こした場合は、従来困難であった、亜鉛メッキ鋼材に対するポリプロピレン樹脂系粉体塗料の適用が可能になる。
【００１５】
【発明の実施の形態】
本発明により防食塗装が施される亜鉛メッキ鋼材は、橋梁等の建築物を構築するために通常用いられる公知のものであり、特に限定されるものではない。
【００１６】
このような亜鉛メッキ鋼材に対して本発明の防食塗装方法を適用する場合は、先ず、亜鉛メッキ鋼材の表面をリン酸亜鉛処理する。ここで、リン酸亜鉛処理は、金属表面を不動態化させてその耐食性を高めるための表面処理方法として従来から広く知られているものであり、その具体的な方法は特に限定されるものではないが、通常、リン酸亜鉛処理液を亜鉛メッキ鋼材の表面に適用することにより実施することができる。
【００１７】
ここで、リン酸亜鉛処理液としては、例えば、リン酸二水素亜鉛と硝酸亜鉛とを含む処理液を挙げることができる。また、このようなリン酸亜鉛処理液を亜鉛メッキ鋼材の表面に適用するための方法としては、例えば、リン酸亜鉛処理液を亜鉛メッキ鋼材の表面にスプレーする方法、リン酸亜鉛処理液中に亜鉛メッキ鋼材を浸漬する方法などを採用することができる。
【００１８】
上述のようなリン酸亜鉛処理が施された亜鉛メッキ鋼材に対しては、所望により、さらにプライマー処理を施してもよい。ここで、プライマー処理は、塗装が施される金属表面に対して耐食性および塗膜との接着性を高めることができる表面処理方法として従来から知られた処理であり、その具体的な方法は特に限定されるものではないが、通常、リン酸亜鉛処理が施された亜鉛メッキ鋼材の表面に対してプライマー処理剤を適用することにより実施することができる。
【００１９】
ここで、プライマー処理剤としては、例えば、エポキシ系樹脂を有機溶剤に溶解させたものや塩化ゴム系などの公知の各種の有機物系プライマー処理剤および酸化クロム−コロイダルシリカ系等の公知の各種の無機物系プライマー処理剤を用いることができる。このようなプライマー処理剤をリン酸亜鉛処理後の亜鉛メッキ鋼材の表面に対して適用するための方法としては、例えば、プライマー処理剤中に当該亜鉛メッキ鋼材を浸漬する方法、プライマー処理剤を当該亜鉛メッキ鋼材の表面にスプレーする方法などを採用することができる。
【００２０】
なお、このようなプライマー処理を施した場合は、亜鉛メッキ鋼材と後述する粉体塗料による塗膜との接着性をより高めることができ、亜鉛メッキ鋼材に対して当該塗膜による防食性をより安定に付与することができる。また、この場合は、亜鉛メッキ鋼材に対して従来適用が困難であったポリプロピレン樹脂系の粉体塗料を適用することができるようになる。
【００２１】
次に、上述のようなリン酸亜鉛処理、またはリン酸亜鉛処理とプライマー処理の両方が施された亜鉛メッキ鋼材（以下、「表面処理後の亜鉛メッキ鋼材」と云う場合がある）の表面に対し、膜形成性成分としてのポリオレフィン系樹脂を含むポリオレフイン系樹脂粉体塗料による塗膜を付与する。ここで、ポリオレフィン系樹脂としては、例えば、ポリエチレン樹脂、変性ポリエチレン樹脂、ポリプロピレン樹脂、変性ポリプロピレン樹脂、エチレン−アクリル酸共重合体樹脂、エチレン−メタクリル酸共重合体樹脂、エチレン−酢酸ビニル共重合体樹脂等を用いることができる。これらのポリオレフィン系樹脂は、２種以上が混合して用いられてもよい。なお、ここに挙げた各ポリオレフィン系樹脂の好ましい態様のものは下記の通りである。
【００２２】
（ポリエチレン樹脂）
１９０℃におけるメルトフローレートが１〜８０ｇ／１０分であり、かつ密度が０．９１〜０．９４ｇ／ｃｍ3のものである。メルトフローレートが１ｇ／１０分未満の場合は、溶融性が不十分になり、塗膜表面の平滑性が損なわれるおそれがある。逆に、８０ｇ／１０分を超える場合は、樹脂物性が極端に低下し、粉体塗料として利用できないおそれがある。一方、密度が０．９１ｇ／ｃｍ3未満の場合は、ゴム弾性が強くなり、粉末化が困難になるため、粉体塗料として利用できないおそれがある。逆に、０．９４ｇ／ｃｍ3を超える場合は、塗膜の強度が低下するおそれがある。
【００２３】
（変性ポリエチレン樹脂）
ポリエチレン樹脂、特に上述の好ましい態様のポリエチレン樹脂を不飽和カルボン酸およびその無水物のうちの一つによりグラフト変性したものである。因に、不飽和カルボン酸およびその無水物としては、例えば、アクリル酸、メタクリル酸、マレイン酸、無水マレイン酸、フマル酸、イタコン酸および無水イタコン酸などを挙げることができる。
【００２４】
（ポリプロピレン樹脂）
２３０℃におけるメルトフローレートが１〜１００ｇ／１０分のものである。メルトフローレートが１ｇ／１０分未満の場合は、溶融性が不十分になり、塗膜表面の平滑性が損なわれるおそれがある。逆に、１００ｇ／１０分を超える場合は、樹脂物性が極端に低下し、粉体塗料として利用できないおそれがある。
【００２５】
（変性ポリプロピレン樹脂）
ポリプロピレン樹脂、特に上述の好ましい態様のポリプロピレン樹脂を不飽和カルボン酸およびその無水物のうちの一つによりグラフト変性したものである。因に、不飽和カルボン酸およびその無水物としては、例えば、アクリル酸、メタクリル酸、マレイン酸、無水マレイン酸、フマル酸、イタコン酸および無水イタコン酸などを挙げることができる。
【００２６】
（エチレン−アクリル酸共重合体樹脂）
アクリル酸の割合が１〜２０重量％であり、かつ１９０℃におけるメルトフローレートが５〜５０ｇ／１０分のものである。なお、ここで言うアクリル酸の割合とは、目的とするエチレン−アクリル酸共重合体樹脂を製造する場合に用いるモノマー成分としてのアクリル酸の割合をいう。
【００２７】
アクリル酸の割合が１重量％未満の場合は、表面処理後の亜鉛メッキ鋼材に対する接着性が不十分になり、亜鉛メッキ鋼材に対して耐久性のある防食性塗膜を付与するのが困難になるおそれがある。逆に、アクリル酸の割合が２０重量％を超える場合は、樹脂物性が極端に低下し、エチレン−アクリル酸共重合体樹脂を粉体塗料として使用することができないおそれがある。一方、エチレン−アクリル酸共重合体樹脂のメルトフローレートが５ｇ／１０分未満の場合は、溶融性が不十分になり、塗膜表面の平滑性が損なわれるおそれがある。逆に、５０ｇ／１０分を超える場合は、融点が低下して粉末化が困難になるため、粉体塗料として利用できないおそれがある。
【００２８】
（エチレン−メタクリル酸共重合体樹脂）
メタクリル酸の割合が５〜２０重量％であり、かつ１９０℃におけるメルトフローレートが３〜５０ｇ／１０分のものである。なお、ここで言うメタクリル酸の割合とは、目的とするエチレン−メタクリル酸共重合体樹脂を製造する場合に用いるモノマー成分としてのメタクリル酸の割合をいう。
【００２９】
メタクリル酸の割合が３重量％未満の場合は、表面処理後の亜鉛メッキ鋼材に対する接着性が低下し、亜鉛メッキ鋼材に対して耐久性のある防食性塗膜を付与するのが困難になるおそれがある。逆に、メタクリル酸の割合が２０重量％を超える場合は、樹脂物性が極端に低下し、エチレン−メタクリル酸共重合体樹脂を粉体塗料として使用することができないおそれがある。一方、エチレン−メタクリル酸共重合体樹脂のメルトフローレートが３ｇ／１０分未満の場合は、溶融性が不十分になり、塗膜表面の平滑性が損なわれるおそれがある。逆に、５０ｇ／１０分を超える場合は、軟化点が低下して粉末化が困難になるため、粉体塗料として利用できないおそれがある。
【００３０】
本発明で用いられる、上述のポリオレフィン系樹脂粉体塗料として好ましいものは、それによる塗膜と表面処理後の亜鉛メッキ鋼材との接着性および当該塗膜の耐久性をより高めることができる点で下記のものである。
【００３１】
▲１▼エチレン−アクリル酸共重合体樹脂５０〜１００重量％とポリエチレン樹脂０〜５０重量％とを含む粉体塗料。ここで、エチレン−アクリル酸共重合体樹脂およびポリエチレン樹脂としては、それぞれ上述の好ましい態様のものを用いるのが好ましい。
▲２▼エチレン−メタクリル酸共重合体樹脂５０〜１００重量％とポリエチレン樹脂０〜５０重量％とを含む粉体塗料。ここで、エチレン−メタクリル酸共重合体樹脂およびポリエチレン樹脂としては、それぞれ上述の好ましい態様のものを用いるのが好ましい。
▲３▼変性ポリエチレン樹脂５０〜１００重量％とポリエチレン樹脂０〜５０重量％とを含む粉体塗料。ここで、変性ポリエチレン樹脂およびポリエチレン樹脂としては、それぞれ上述の好ましい態様のものを用いるのが好ましい。
▲４▼変性ポリプロピレン樹脂５０〜１００重量％とポリプロピレン樹脂０〜５０重量％とを含む粉体塗料。ここで、変性ポリプロピレン樹脂およびポリプロピレン樹脂としては、それぞれ上述の好ましい態様のものを用いるのが好ましい。
【００３２】
このような好ましい粉体塗料は、次のようにして製造することができる。先ず、所定のポリオレフィン樹脂をスーパーミキサーやヘンシェルミキサーなどを用いて所定の割合で混合する。そして、この混合物を混練押出機、加熱ロール、バンバリーミキサーまたはニーダーなどの混練り機を用いて加熱溶融混練した後に例えばペレット状に成形し、これを機械粉砕法、液体窒素を用いる冷凍粉砕法などの手法により微粉末状に粉砕する。なお、粉砕時には、粉体塗料粒子の平均粒径が５０〜５００μｍになるよう設定するのが好ましく、７０〜３５０μｍになるよう設定するのがより好ましい。この平均粒径が５０μｍ未満の場合は、粉末流動性が低下し、塗装が困難になるおそれがある。逆に、５００μｍを超える場合は、塗膜の平滑性および均一性が得られないおそれがある。
【００３３】
なお、上述の粉体塗料には、必要に応じて着色剤、熱安定化剤、紫外線吸収剤、ラジカル捕捉剤、滑剤、粉砕助剤などの各種の添加剤が適宜含まれていてもよい。
【００３４】
表面処理後の亜鉛メッキ鋼材に対して上述の粉体塗料を塗装する際には、流動浸漬法、静電塗着法、溶射法および散布法などの公知の粉体塗装方法を採用することができる。
【００３５】
上述のような本発明の防食塗装方法では、亜鉛メッキ鋼材に対してリン酸亜鉛処理を施し、さらに必要に応じてプライマー処理を施してからポリオレフィン系樹脂粉体塗料による塗膜を付与しているため、塩水や酸性雨等を含む腐食性環境下でも長期間に渡って劣化しにくい防食性を亜鉛メッキ鋼材に対して付与することができる。また、この防食塗装方法は、従来のように鋼材に亜鉛メッキを施す際の余熱を利用する必要が無く、鋼材に対して亜鉛メッキを施すための工程と区別して実施することができるので、汎用性があり、実用性が高い。
【００３６】
【実施例】
以下、実施例および比較例により本発明をさらに詳しく説明するが、本発明はこれらの実施例等により何ら限定されるものではない。
【００３７】
粉体塗料の調製
樹脂材料として下記の８種類のポリオレフィン系樹脂を単独で又は混合して用い、表１に示すＡ〜Ｌの１２種類の粉体塗料を調製した。
（１）エチレン−アクリル酸共重合体樹脂（日本ポリケム株式会社の商品名“ノバテックＡ２１０Ｍ”：アクリル酸割合＝７重量％、メルトフローレート＝９ｇ／１０分）
（２）エチレン−アクリル酸共重合体樹脂（日本ポリケム株式会社の商品名“ノバテックＡ２２０Ｓ”：アクリル酸割合＝７重量％、メルトフローレート１７ｇ／１０分）
（３）エチレン−メタクリル酸共重合体樹脂（三井デュポン株式会社の商品名“ニュークレルＮ１１０８Ｃ”：メタクリル酸割合＝１１重量％、メルトフローレート＝８ｇ／１０分）
（４）エチレン−メタクリル酸共重合体樹脂（三井デュポン株式会社の商品名“ニュークレルＮ１０３５”：メタクリル酸割合＝１０重量％、メルトフローレート＝３６ｇ／１０分）
（５）ポリエチレン樹脂（三井化学株式会社の商品名“ウルトゼックス２５１００”：メルトフローレート＝１０ｇ／１０分、密度＝０．９２５ｇ／ｃｍ3）
（６）変性ポリエチレン樹脂（三井化学株式会社の商品名“アドマーＮＥ１５０”：メルトフローレート＝１６ｇ／１０分）
（７）ポリプロピレン樹脂（住友化学工業株式会社の商品名“ノーブレンＺ１３１”：メルトフローレート＝３２ｇ／１０分）
（８）変性ポリプロピレン樹脂（三井化学株式会社の商品名“アドマーＡＴ９７０”：メルトフローレート＝３６ｇ／１０分）
【００３８】
ここで、単独のポリオレフィン系樹脂を用いた粉体塗料（粉体塗料Ａ、Ｃ、Ｅ、Ｇ、ＩおよびＫ）は、押出機を用いてポリオレフィン系樹脂を１９０℃で溶融してペレットを作成し、得られたペレットを機械粉砕して粒径が７０〜３５０μｍになるように分級して調製した。
【００３９】
一方、ポリオレフィン系樹脂の混合物を用いた粉体塗料（粉体塗料Ｂ、Ｄ、Ｆ、Ｈ、ＪおよびＬ）は、ヘンシェルミキサーを用いてポリオレフィン系樹脂を表１に示す割合で予備混合し、この予備混合物を押出機を用いて１９０℃で溶融混練して得られたペレットを機械粉砕して粒径が７０〜３５０μｍになるように分級して調製した。
【００４０】
【表１】
実施例１〜８
（工程１）
亜鉛メッキ鋼板のテストピース（日本テストパネル工業株式会社の商品名“溶融亜鉛メッキ ＨＤＺ”：大きさ＝７０×１５０×６ｍｍt）を脱脂処理して表面調整し、これを７０℃のリン酸亜鉛処理液（日本パーカライジング株式会社の商品名“パルボンド３３０８”）中に４分間浸漬した。その後、テストピースを水洗して乾燥し、表面がリン酸亜鉛処理された亜鉛メッキ鋼板を得た。
【００４２】
（工程２）
工程１で得られた、表面がリン酸亜鉛処理された亜鉛メッキ鋼板に対し、表２に示す種類の粉体塗料を流動浸漬法により塗装した。ここでは、先ず、多孔質の槽底部を有する流動浸漬槽内に粉体塗料を入れ、この状態で槽底部から空気を送り込むことにより安定した流動状態を確保した。そして、リン酸亜鉛処理された亜鉛メッキ鋼板を２２０℃のオーブン内で２５分間予備加熱した後、その流動浸漬槽内に１５秒間浸漬した。その後、流動浸漬槽から亜鉛メッキ鋼板を取り出し、これを２００℃のオーブン内で５分間後加熱を実施してから室温まで冷却した。これにより、防食塗装が施された亜鉛メッキ鋼板を得た。
【００４３】
比較例１〜４
リン酸亜鉛処理していない亜鉛メッキ鋼板のテストピースを用いた点を除いて実施例１、３、５および７の場合と同様に操作し、防食塗装が施された亜鉛メッキ鋼板を得た。
【００４４】
実施例９〜２４
実施例１〜８の工程１で得られた、表面がリン酸亜鉛処理された亜鉛メッキ鋼板に対してさらにプライマー処理を施した。ここでは、プライマー処理剤としてエポキシ系樹脂を成分とする有機物系プライマー処理剤（田辺化学工業株式会社の商品名”マルチグリッププライマー”）または酸化クロム−コロイダルシリカを成分とする無機物系プライマー処理剤（関西ペイント株式会社の商品名”コスマー１００”）を用い、リン酸亜鉛処理された亜鉛メッキ鋼板をこのプライマー処理剤中に３０秒間浸漬した後に室温で乾燥した。なお、各実施例において使用したプライマー処理剤の種類は表２に示す通りである。
【００４５】
このようにして得られた、リン酸亜鉛処理およびプライマー処理の両処理が施された亜鉛メッキ鋼板に対し、実施例１〜８の工程２の場合と同様にして粉体塗料を適用した。但し、実施例９〜２０については亜鉛メッキ鋼板の予備加熱時の温度および時間をそれぞれ２５０℃および５分間に変更し、また、実施例２１〜２４については亜鉛メッキ鋼板の予備加熱時の温度を２５０℃に時間を２５分間にそれぞれ変更した。これにより、防食塗装が施された亜鉛メッキ鋼板を得た。
【００４６】
比較例５
リン酸亜鉛処理およびプライマー処理を共に施していない亜鉛メッキ鋼板のテストピースを用いた点を除いて実施例９の場合と同様に操作し、防食塗装が施された亜鉛メッキ鋼板を得た。
【００４７】
比較例６
リン酸亜鉛処理を施さずに実施例９の場合と同様のプライマー処理のみを施した亜鉛メッキ鋼板のテストピースを用いた点を除いて実施例９の場合と同様に操作し、防食塗装が施された亜鉛メッキ鋼板を得た。
【００４８】
比較例７
リン酸亜鉛処理およびプライマー処理を共に施していない亜鉛メッキ鋼板のテストピースを用いた点を除いて実施例１７の場合と同様に操作し、防食塗装が施された亜鉛メッキ鋼板を得た。
【００４９】
比較例８
リン酸亜鉛処理を施さずに実施例１７の場合と同様のプライマー処理のみを施した亜鉛メッキ鋼板のテストピースを用いた点を除いて実施例１７の場合と同様に操作し、防食塗装が施された亜鉛メッキ鋼板を得た。
【００５０】
比較例９
リン酸亜鉛処理およびプライマー処理を共に施していない亜鉛メッキ鋼板のテストピースを用いた点を除いて実施例２１の場合と同様に操作し、防食塗装が施された亜鉛メッキ鋼板を得た。
【００５１】
比較例１０
リン酸亜鉛処理を施さずに実施例２１の場合と同様のプライマー処理のみを施した亜鉛メッキ鋼板のテストピースを用いた点を除いて実施例２１の場合と同様に操作し、防食塗装が施された亜鉛メッキ鋼板を得た。
【００５２】
評価
実施例１〜２４および比較例１〜１０で得られた、防食塗装が施された亜鉛メッキ鋼板について、粉体塗料による防食塗膜の性能を評価した。結果を表２に示す。なお、評価の方法は次の通りである。
【００５３】
（接着力）
塗膜に幅２５ｍｍの平行ノッチをカッターナイフで金属素材まで達するように入れた。そして、引張試験機を用いて塗膜を１８０度の方向に５０ｍｍ／分の速度で剥離し、接着強度を測定した。なお、接着強度が大きい程、亜鉛メッキ鋼板に対する塗膜の密着性（接着性）は良好である。
【００５４】
（塩水噴霧試験）
ＪＩＳＫ５４００−９．１に規定された試験方法に従って実施した。すなわち、塗膜上の交差する２本の対角線上に予めノッチをカッターナイフで金属素材まで達するように入れ、これを３５℃の温度で５００時間（実施例１〜８および比較例１〜４の場合）または１，０００時間（実施例９〜２４および比較例５〜１０の場合）塩水噴霧に曝した後、塗膜の状況を観察した。評価の基準は下記の通りである。
【００５５】
◎：塗膜の膨れ、ノッチ部からの剥離ともに認められず、耐食性は良好。
○：塗膜に僅かに膨れが認められるが、ノッチ部からの剥離は認められず、耐食性は良好。
×：塗膜の膨れ及びノッチ部からの剥離が認められ、耐食性は不良。
【００５６】
【表２】
【表３】
表２（表２−１および表２−２）から明らかなように、本発明の防食塗装方法を採用した亜鉛メッキ鋼板の場合（実施例１〜２４）は、いずれも塗膜の接着性が良好であり、耐食性に優れていたが、リン酸亜鉛処理を施していない亜鉛メッキ鋼板（プライマー処理のみを施したものを含む）を用いた場合（比較例１〜１０）には耐食性が認められなかった。なお、リン酸亜鉛処理とプライマー処理の両方の処理が施された場合（実施例９〜２４）は、リン酸亜鉛処理のみを施した場合（実施例１〜８）に比べて防食塗膜の接着性がさらに良好であり、また、耐食性も長期間安定に維持され得ることがわかる。
【００５９】
【発明の効果】
本発明に係る亜鉛メッキ鋼材の防食塗装方法は、亜鉛メッキ鋼材に対して予めリン酸亜鉛処理を施した後にポリオレフィン系樹脂粉体塗料による塗膜を付与しているので、亜鉛メッキ鋼材に対して腐食性環境下での耐久性が良好な防食性を付与することができる。また、この方法は、従来必要であった亜鉛メッキ時の余熱の利用が必要でないため実用的である。
【００６０】
なお、本発明の防食塗装方法において、リン酸亜鉛処理後の亜鉛メッキ鋼材に対してさらにプライマー処理を施した場合は、亜鉛メッキ鋼材とポリオレフィン系樹脂粉体塗料による塗膜との接着性をより高めることができ、当該塗膜による防食性を亜鉛メッキ鋼材に対してより安定に付与することができる。また、この場合は、これまで亜鉛メッキ鋼材に対する適用が困難であったポリプロピレン樹脂系の粉体塗料を利用することができる。[0001]
[Technical field to which the invention belongs]
The present invention relates to an anticorrosion coating method, and more particularly to an anticorrosion coating method for imparting anticorrosion properties to a galvanized steel material.
[0002]
[Prior art and its problems]
Steel materials used for constructing bridges, power transmission towers, train overhead posts, communication cable posts, and the like are often galvanized on the surface in order to enhance corrosion resistance. A steel material to which such galvanization is applied can exhibit good corrosion resistance in a normal atmosphere. However, in galvanizing, the plating layer often disappears in several years in corrosive environments such as an environment near a beach that is easily exposed to salt water or an environment that is susceptible to acid rain. Below, it is difficult to impart durable corrosion protection to the steel.
[0003]
For this reason, in order to improve the corrosion resistance of the galvanized steel material, an attempt has been made to apply a powder resin coating on the surface thereof. For example, JP-A-60-143952 discloses a resin coating for civil engineering and construction in which the surface of a galvanized iron member is powder-coated with a copolymer resin powder of ethylene and α, β-unsaturated carboxylic acid. An iron member is disclosed. However, since such resin-coated iron members for civil engineering and construction are not sufficiently adhesive to the coating film formed by powder coating, peeling of the coating film and embrittlement of the galvanized plate in the corrosive environment as described above The anticorrosion property is still difficult to maintain stably for a long time.
[0004]
Attempts have also been made to apply a saturated polyester resin powder coating on the galvanized layer using the residual heat when galvanizing the steel material. In this case, since a coating film having relatively good adhesion can be applied on the galvanized layer, the corrosion resistance of the galvanized steel material in a corrosive environment is maintained relatively stably for a long time. The paint can be applied only when and where the steel can be galvanized. For this reason, such an anticorrosion coating method lacks versatility and lacks practicality (for example, refer to rust prevention management, (5) 1 to 12, 1997).
[0005]
An object of the present invention is to realize a practical anticorrosion coating method that can impart stable anticorrosive properties to galvanized steel materials over a long period of time even in a corrosive environment.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors performed zinc phosphate treatment on the surface of the galvanized steel material, and further applied primer treatment as necessary, followed by coating with a polyolefin resin powder coating material. When the film was applied, it was found that a resin film having good durability in an adhesive and corrosive environment was applied to the galvanized steel material, and the present invention was completed.
[0007]
That is, the anticorrosion coating method of the present invention is for imparting anticorrosion properties to a galvanized steel material, a step of treating the surface of the galvanized steel material with zinc phosphate, and a surface of the galvanized steel material treated with zinc phosphate. And a step of applying a coating film with a polyolefin resin powder coating. In addition, this anticorrosion coating method may further include a step of priming the surface of the zinc-plated steel material treated with zinc phosphate before applying the coating film with the polyolefin resin powder coating.
[0008]
The polyolefin resin powder paint used here contains, for example, 50 to 100% by weight of an ethylene-acrylic acid copolymer resin and 0 to 50% by weight of a polyethylene resin. In this case, as the ethylene-acrylic acid copolymer resin, one having an acrylic acid ratio of 1 to 20% by weight and a melt flow rate at 190 ° C. of 5 to 50 g / 10 min is usually used.
[0009]
Moreover, the polyolefin-type resin powder coating material used by the other form of this invention contains 50-100 weight% of ethylene-methacrylic acid copolymer resins, and 0-50 weight% of polyethylene resins, for example. In this case, as the ethylene-methacrylic acid copolymer resin, those having a methacrylic acid ratio of 5 to 20% by weight and a melt flow rate at 190 ° C. of 3 to 50 g / 10 min are usually used.
[0010]
The polyolefin resin powder coating used in still another embodiment of the present invention contains, for example, a modified polyethylene resin 50 to 100% by weight and a polyethylene resin 0 to 50% by weight. In this case, as the modified polyethylene resin, usually a polyethylene resin obtained by graft modification with an unsaturated carboxylic acid and one of its anhydrides is used.
[0011]
The polyethylene resin used in each of the above-described forms usually has a melt flow rate at 190 ° C. of 1 to 80 g / 10 minutes and a density of 0.91 to 0.94 g / cm.Threebelongs to.
[0012]
The polyolefin resin powder coating used in still another embodiment of the present invention contains, for example, a modified polypropylene resin 50 to 100% by weight and a polypropylene resin 0 to 50% by weight. In this case, as the modified polypropylene resin, usually, a polypropylene resin obtained by graft modification with an unsaturated carboxylic acid and one of its anhydrides is used. The polypropylene resin used here usually has a melt flow rate at 230 ° C. of 1 to 100 g / 10 min.
[0013]
In the anticorrosion coating method of the present invention, the zinc phosphate treatment and the primer treatment itself are known rust prevention methods. However, in the present invention, the coating formed by the zinc phosphate treatment or the primer treatment is used as a base agent without being exposed on the surface, and the polyolefin-based resin coating is made strong against the galvanized steel by its anchor effect. Glue. The mechanism that improves the adhesion and durability of polyolefin resin coatings when galvanized steel is pre-treated with zinc phosphate is not trivial, but is formed by galvanized surface and zinc phosphate treatment Strong adhesive strength between coatings, good adhesion between zinc phosphate coating and polyolefin resin coatings, good coating between zinc phosphate coating and primer coating The strong anchorage due to the interaction between the coating formed by primer treatment and the polar group contained in the polyolefin resin coating and the synergistic action, and the excellent anchor effect Inferred.
[0014]
In the present invention, when the primer treatment is further applied to the zinc-plated steel material after the zinc phosphate treatment, it is possible to apply the polypropylene resin powder coating material to the zinc-plated steel material, which has been difficult in the past. .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The galvanized steel material to which the anticorrosion coating is applied according to the present invention is a known one that is usually used for constructing a building such as a bridge, and is not particularly limited.
[0016]
When applying the anticorrosion coating method of the present invention to such a galvanized steel material, first, the surface of the galvanized steel material is treated with zinc phosphate. Here, the zinc phosphate treatment has been widely known as a surface treatment method for passivating a metal surface to enhance its corrosion resistance, and its specific method is not particularly limited. Usually, it can be carried out by applying a zinc phosphate treatment solution to the surface of the galvanized steel.
[0017]
Here, examples of the zinc phosphate treatment liquid include a treatment liquid containing zinc dihydrogen phosphate and zinc nitrate. Moreover, as a method for applying such a zinc phosphate treatment liquid to the surface of a galvanized steel material, for example, a method of spraying a zinc phosphate treatment liquid on the surface of a galvanized steel material, A method of immersing a galvanized steel material can be employed.
[0018]
The galvanized steel material that has been subjected to the zinc phosphate treatment as described above may be further subjected to a primer treatment if desired. Here, the primer treatment is a treatment conventionally known as a surface treatment method capable of enhancing the corrosion resistance and adhesion to the coating film on the metal surface to be coated, and the specific method is particularly Although it is not limited, it can be normally carried out by applying a primer treatment agent to the surface of the zinc-plated steel material that has been subjected to the zinc phosphate treatment.
[0019]
Here, as the primer treating agent, for example, various known organic primer treating agents such as those obtained by dissolving an epoxy resin in an organic solvent or chlorinated rubber-based and various known various types such as chromium oxide-colloidal silica-based. An inorganic primer treatment agent can be used. Examples of a method for applying such a primer treatment agent to the surface of a galvanized steel material after zinc phosphate treatment include, for example, a method of immersing the galvanized steel material in a primer treatment agent, A method of spraying on the surface of the galvanized steel can be employed.
[0020]
In addition, when such a primer treatment is applied, the adhesion between the galvanized steel material and a coating film by a powder coating described later can be further increased, and the corrosion resistance by the coating film can be further improved against the galvanized steel material. It can be stably applied. Moreover, in this case, it becomes possible to apply a polypropylene resin-based powder coating that has been difficult to apply to galvanized steel.
[0021]
Next, on the surface of the zinc-plated steel material that has been subjected to the zinc phosphate treatment as described above, or both the zinc phosphate treatment and the primer treatment (hereinafter may be referred to as “galvanized steel material after the surface treatment”). On the other hand, a coating film by a polyolefin resin powder coating containing a polyolefin resin as a film-forming component is applied. Here, as the polyolefin resin, for example, polyethylene resin, modified polyethylene resin, polypropylene resin, modified polypropylene resin, ethylene-acrylic acid copolymer resin, ethylene-methacrylic acid copolymer resin, ethylene-vinyl acetate copolymer Resin or the like can be used. Two or more of these polyolefin resins may be used in combination. In addition, the thing of the preferable aspect of each polyolefin resin quoted here is as follows.
[0022]
(Polyethylene resin)
The melt flow rate at 190 ° C. is 1 to 80 g / 10 min, and the density is 0.91 to 0.94 g / cm.Threebelongs to. When the melt flow rate is less than 1 g / 10 minutes, the meltability becomes insufficient and the smoothness of the coating film surface may be impaired. On the other hand, when it exceeds 80 g / 10 min, the resin physical properties are extremely lowered and there is a possibility that it cannot be used as a powder coating material. On the other hand, the density is 0.91 g / cmThreeIf it is less than 1, the rubber elasticity becomes strong and powdering becomes difficult, so there is a possibility that it cannot be used as a powder coating. Conversely, 0.94 g / cmThreeIf it exceeds 1, the strength of the coating film may be reduced.
[0023]
(Modified polyethylene resin)
A polyethylene resin, in particular, the above-described preferred embodiment of the polyethylene resin is graft-modified with an unsaturated carboxylic acid and one of its anhydrides. Incidentally, examples of the unsaturated carboxylic acid and its anhydride include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, and itaconic anhydride.
[0024]
(Polypropylene resin)
The melt flow rate at 230 ° C. is 1 to 100 g / 10 min. When the melt flow rate is less than 1 g / 10 minutes, the meltability becomes insufficient and the smoothness of the coating film surface may be impaired. On the other hand, if it exceeds 100 g / 10 min, the physical properties of the resin are extremely lowered and there is a possibility that it cannot be used as a powder coating material.
[0025]
(Modified polypropylene resin)
A polypropylene resin, particularly a polypropylene resin of the above-mentioned preferred embodiment, is obtained by graft modification with an unsaturated carboxylic acid and one of its anhydrides. Incidentally, examples of the unsaturated carboxylic acid and its anhydride include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, and itaconic anhydride.
[0026]
(Ethylene-acrylic acid copolymer resin)
The ratio of acrylic acid is 1 to 20% by weight, and the melt flow rate at 190 ° C. is 5 to 50 g / 10 min. In addition, the ratio of acrylic acid said here means the ratio of acrylic acid as a monomer component used when manufacturing the target ethylene-acrylic acid copolymer resin.
[0027]
When the ratio of acrylic acid is less than 1% by weight, the adhesion to the galvanized steel after the surface treatment becomes insufficient, making it difficult to provide a durable anticorrosive coating film on the galvanized steel. There is a risk. On the other hand, when the proportion of acrylic acid exceeds 20% by weight, the physical properties of the resin are extremely lowered, and the ethylene-acrylic acid copolymer resin may not be used as a powder coating material. On the other hand, when the melt flow rate of the ethylene-acrylic acid copolymer resin is less than 5 g / 10 minutes, the meltability becomes insufficient and the smoothness of the coating film surface may be impaired. On the other hand, when it exceeds 50 g / 10 minutes, the melting point is lowered and powdering becomes difficult, so that it may not be used as a powder coating.
[0028]
(Ethylene-methacrylic acid copolymer resin)
The ratio of methacrylic acid is 5 to 20% by weight, and the melt flow rate at 190 ° C. is 3 to 50 g / 10 min. In addition, the ratio of methacrylic acid said here means the ratio of methacrylic acid as a monomer component used when manufacturing the target ethylene-methacrylic acid copolymer resin.
[0029]
When the ratio of methacrylic acid is less than 3% by weight, the adhesion to the galvanized steel after the surface treatment is lowered, and it may be difficult to give a durable anticorrosive coating film to the galvanized steel. There is. On the contrary, when the ratio of methacrylic acid exceeds 20% by weight, the resin physical properties are extremely lowered, and the ethylene-methacrylic acid copolymer resin may not be used as a powder coating material. On the other hand, when the melt flow rate of the ethylene-methacrylic acid copolymer resin is less than 3 g / 10 minutes, the meltability becomes insufficient and the smoothness of the coating film surface may be impaired. On the other hand, when it exceeds 50 g / 10 minutes, the softening point is lowered and powdering becomes difficult, so that it may not be used as a powder coating.
[0030]
What is preferable as the above-described polyolefin-based resin powder coating used in the present invention is that the adhesion between the coating film and the galvanized steel after the surface treatment and the durability of the coating film can be further improved. It is the following.
[0031]
(1) A powder coating containing 50 to 100% by weight of ethylene-acrylic acid copolymer resin and 0 to 50% by weight of polyethylene resin. Here, as the ethylene-acrylic acid copolymer resin and the polyethylene resin, it is preferable to use the above-described preferred embodiments, respectively.
(2) A powder coating containing 50 to 100% by weight of ethylene-methacrylic acid copolymer resin and 0 to 50% by weight of polyethylene resin. Here, as the ethylene-methacrylic acid copolymer resin and the polyethylene resin, it is preferable to use the above-mentioned preferred embodiments, respectively.
(3) A powder coating containing 50 to 100% by weight of modified polyethylene resin and 0 to 50% by weight of polyethylene resin. Here, as a modified polyethylene resin and a polyethylene resin, it is preferable to use the thing of the above-mentioned preferable aspect, respectively.
(4) A powder coating containing 50 to 100% by weight of modified polypropylene resin and 0 to 50% by weight of polypropylene resin. Here, as a modified polypropylene resin and a polypropylene resin, it is preferable to use the thing of the above-mentioned preferable aspect, respectively.
[0032]
Such a preferable powder coating material can be manufactured as follows. First, a predetermined polyolefin resin is mixed at a predetermined ratio using a super mixer or a Henschel mixer. Then, this mixture is heated, melted and kneaded using a kneader such as a kneading extruder, heating roll, Banbury mixer or kneader, and then formed into a pellet, for example, and this is mechanically pulverized, frozen pulverized using liquid nitrogen, etc. The powder is pulverized by the above method. At the time of pulverization, the average particle diameter of the powder coating particles is preferably set to 50 to 500 μm, and more preferably set to 70 to 350 μm. When this average particle diameter is less than 50 μm, the powder fluidity is lowered, and coating may be difficult. On the other hand, when it exceeds 500 μm, the smoothness and uniformity of the coating film may not be obtained.
[0033]
The above-mentioned powder coating material may appropriately contain various additives such as a colorant, a heat stabilizer, an ultraviolet absorber, a radical scavenger, a lubricant, and a grinding aid as necessary.
[0034]
When the above-mentioned powder coating is applied to the galvanized steel after the surface treatment, a known powder coating method such as a fluid dipping method, an electrostatic coating method, a thermal spraying method, or a spraying method may be employed. it can.
[0035]
In the anticorrosion coating method of the present invention as described above, a zinc phosphate treatment is applied to a galvanized steel material, and further a primer treatment is applied as necessary, and then a coating film by a polyolefin resin powder coating is applied. Therefore, it is possible to impart to the galvanized steel a corrosion resistance that does not deteriorate over a long period of time even in a corrosive environment including salt water or acid rain. In addition, this anticorrosion coating method does not require the use of residual heat when galvanizing steel as in the prior art, and can be carried out separately from the process for galvanizing steel. And practicality is high.
[0036]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these Examples.
[0037]
Powder coating preparation
The following eight types of polyolefin-based resins were used alone or in combination as resin materials, and 12 types of powder coatings A to L shown in Table 1 were prepared.
(1) Ethylene-acrylic acid copolymer resin (trade name “Novatech A210M” of Nippon Polychem Co., Ltd .: acrylic acid ratio = 7 wt%, melt flow rate = 9 g / 10 min)
(2) Ethylene-acrylic acid copolymer resin (trade name “Novatech A220S” of Nippon Polychem Co., Ltd .: acrylic acid ratio = 7% by weight, melt flow rate 17 g / 10 min)
(3) Ethylene-methacrylic acid copolymer resin (trade name “Nucleel N1108C” of Mitsui DuPont Co., Ltd .: methacrylic acid ratio = 11 wt%, melt flow rate = 8 g / 10 min)
(4) Ethylene-methacrylic acid copolymer resin (trade name “Nucleel N1035” of Mitsui DuPont Co., Ltd .: methacrylic acid ratio = 10 wt%, melt flow rate = 36 g / 10 min)
(5) Polyethylene resin (trade name “Ultzex 25100” from Mitsui Chemicals, Inc .: melt flow rate = 10 g / 10 min, density = 0.925 g / cmThree)
(6) Modified polyethylene resin (trade name “Admer NE150” of Mitsui Chemicals, Inc .: melt flow rate = 16 g / 10 min)
(7) Polypropylene resin (trade name “Noblen Z131” of Sumitomo Chemical Co., Ltd .: Melt flow rate = 32 g / 10 min)
(8) Modified polypropylene resin (trade name “Admer AT970” of Mitsui Chemicals, Inc .: Melt flow rate = 36 g / 10 min)
[0038]
Here, powder coatings (powder coatings A, C, E, G, I and K) using a single polyolefin resin are prepared by melting the polyolefin resin at 190 ° C. using an extruder. Then, the obtained pellets were mechanically pulverized and classified so as to have a particle size of 70 to 350 μm.
[0039]
On the other hand, powder coatings using a mixture of polyolefin resins (powder coatings B, D, F, H, J and L) are premixed using a Henschel mixer at a ratio shown in Table 1, The pellets obtained by melt kneading the premixed mixture at 190 ° C. using an extruder were mechanically pulverized and classified so as to have a particle size of 70 to 350 μm.
[0040]
[Table 1]
Examples 1-8
(Process 1)
Test piece of galvanized steel sheet (trade name “Hot galvanized HDZ” by Nippon Test Panel Industry Co., Ltd.): Size = 70 × 150 × 6 mmt) Was degreased and the surface was adjusted, and this was immersed in a 70 ° C. zinc phosphate treatment solution (trade name “Palbond 3308” of Nippon Parkerizing Co., Ltd.) for 4 minutes. Thereafter, the test piece was washed with water and dried to obtain a galvanized steel sheet whose surface was treated with zinc phosphate.
[0042]
(Process 2)
A powder coating of the type shown in Table 2 was applied to the galvanized steel sheet whose surface was treated with zinc phosphate obtained in step 1 by the fluidized dipping method. Here, first, powder coating material was put in a fluid immersion tank having a porous tank bottom, and a stable fluid state was secured by feeding air from the tank bottom in this state. The zinc phosphate-treated galvanized steel sheet was preheated in an oven at 220 ° C. for 25 minutes and then immersed in the fluid immersion tank for 15 seconds. Thereafter, the galvanized steel sheet was taken out from the fluid immersion tank, and after being heated in an oven at 200 ° C. for 5 minutes, it was cooled to room temperature. As a result, a galvanized steel sheet with anticorrosion coating was obtained.
[0043]
Comparative Examples 1-4
A galvanized steel sheet with anticorrosion coating was obtained in the same manner as in Examples 1, 3, 5 and 7, except that a test piece of a galvanized steel sheet not treated with zinc phosphate was used.
[0044]
Examples 9-24
The primer treatment was further applied to the zinc-plated steel sheet whose surface was treated with zinc phosphate obtained in Step 1 of Examples 1 to 8. Here, the organic primer treatment agent (trade name “Multigrip Primer” from Tanabe Chemical Co., Ltd.) containing an epoxy resin as a primer treatment agent or an inorganic primer treatment agent containing chromium oxide-colloidal silica as a component ( Using a product name “Cosmer 100” of Kansai Paint Co., Ltd., a zinc-plated steel sheet treated with zinc phosphate was immersed in this primer treatment agent for 30 seconds and then dried at room temperature. In addition, the kind of primer processing agent used in each Example is as showing in Table 2.
[0045]
The powder coating material was applied to the galvanized steel sheet subjected to both the zinc phosphate treatment and the primer treatment thus obtained in the same manner as in Step 2 of Examples 1-8. However, for Examples 9 to 20, the temperature and time during preheating of the galvanized steel sheet were changed to 250 ° C. and 5 minutes, respectively, and for Examples 21 to 24, the temperature during preheating of the galvanized steel sheet was changed. The time was changed to 250 ° C. for 25 minutes. As a result, a galvanized steel sheet with anticorrosion coating was obtained.
[0046]
Comparative Example 5
A galvanized steel sheet with anticorrosion coating was obtained in the same manner as in Example 9 except that a test piece of a galvanized steel sheet not subjected to both zinc phosphate treatment and primer treatment was used.
[0047]
Comparative Example 6
The anticorrosion coating was applied in the same manner as in Example 9 except that a test piece of galvanized steel sheet that was not subjected to zinc phosphate treatment and was subjected to the same primer treatment as in Example 9 was used. A galvanized steel sheet was obtained.
[0048]
Comparative Example 7
A galvanized steel sheet with anticorrosion coating was obtained in the same manner as in Example 17 except that a test piece of galvanized steel sheet not subjected to zinc phosphate treatment and primer treatment was used.
[0049]
Comparative Example 8
An anticorrosion coating was applied in the same manner as in Example 17 except that a test piece of a galvanized steel sheet that was not subjected to zinc phosphate treatment and was subjected to the same primer treatment as in Example 17 was used. A galvanized steel sheet was obtained.
[0050]
Comparative Example 9
A galvanized steel sheet with anticorrosion coating was obtained in the same manner as in Example 21 except that a test piece of galvanized steel sheet not subjected to either zinc phosphate treatment or primer treatment was used.
[0051]
Comparative Example 10
The anticorrosion coating was applied in the same manner as in Example 21 except that a test piece of a galvanized steel sheet that was not subjected to zinc phosphate treatment and was subjected to the same primer treatment as in Example 21 was used. A galvanized steel sheet was obtained.
[0052]
Evaluation
About the galvanized steel plate in which anticorrosion coating was given obtained in Examples 1-24 and Comparative Examples 1-10, the performance of the anticorrosion coating film by a powder coating material was evaluated. The results are shown in Table 2. The evaluation method is as follows.
[0053]
(Adhesive strength)
A parallel notch with a width of 25 mm was put in the coating film so as to reach the metal material with a cutter knife. And the coating film was peeled in the direction of 180 degree | times at the speed | rate of 50 mm / min using the tensile tester, and the adhesive strength was measured. In addition, the adhesiveness (adhesiveness) of the coating film with respect to a galvanized steel plate is so favorable that adhesive strength is large.
[0054]
(Salt spray test)
The test was conducted according to the test method defined in JISK5400-9.1. That is, a notch is put in advance on the two diagonal lines on the coating film so as to reach the metal material with a cutter knife, and this is carried out at a temperature of 35 ° C. for 500 hours (Examples 1 to 8 and Comparative Examples 1 to 4). Case) or 1,000 hours (in the case of Examples 9 to 24 and Comparative Examples 5 to 10), after being exposed to salt spray, the condition of the coating film was observed. The evaluation criteria are as follows.
[0055]
A: Neither swelling of the coating film nor peeling from the notch is observed, and the corrosion resistance is good.
○: Slight swelling is observed in the coating film, but no peeling from the notch is observed, and the corrosion resistance is good.
X: The swelling of a coating film and peeling from a notch part are recognized, and corrosion resistance is unsatisfactory.
[0056]
[Table 2]
[Table 3]
As is clear from Table 2 (Table 2-1 and Table 2-2), in the case of the galvanized steel sheet employing the anticorrosion coating method of the present invention (Examples 1 to 24), the adhesiveness of the coating film is all. It was good and excellent in corrosion resistance, but corrosion resistance was observed when galvanized steel sheets (including those subjected only to primer treatment) that were not subjected to zinc phosphate treatment (including those subjected to primer treatment only) were used. There wasn't. In addition, when both the zinc phosphate treatment and the primer treatment were performed (Examples 9 to 24), the anticorrosion coating film was compared with the case where only the zinc phosphate treatment was performed (Examples 1 to 8). It can be seen that the adhesiveness is even better, and the corrosion resistance can be maintained stably for a long time.
[0059]
【The invention's effect】
In the anticorrosion coating method of the galvanized steel material according to the present invention, since a coating film by a polyolefin-based resin powder coating is applied to the galvanized steel material in advance after the zinc phosphate treatment, the galvanized steel material is applied to the galvanized steel material. It is possible to impart anticorrosive properties with excellent durability under a corrosive environment. In addition, this method is practical because it does not require the use of residual heat during galvanization, which was conventionally required.
[0060]
In addition, in the anticorrosion coating method of the present invention, when the primer treatment is further applied to the galvanized steel material after the zinc phosphate treatment, the adhesion between the galvanized steel material and the coating film by the polyolefin resin powder coating is more improved. The anticorrosion property by the said coating film can be provided more stably with respect to galvanized steel materials. In this case, a polypropylene resin-based powder coating that has been difficult to apply to galvanized steel materials can be used.
Claims (12)
前記亜鉛メッキ鋼材の表面をリン酸亜鉛処理する工程と、
リン酸亜鉛処理された前記亜鉛メッキ鋼材の前記表面にポリオレフィン系樹脂粉体塗料による塗膜を付与する工程と、
を含む亜鉛メッキ鋼材の防食塗装方法。An anti-corrosion coating method for imparting anti-corrosion properties to galvanized steel,
A step of treating the surface of the galvanized steel with zinc phosphate;
Applying a coating film made of a polyolefin resin powder coating to the surface of the zinc-plated steel material treated with zinc phosphate;
Anticorrosion coating method for galvanized steel including
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11270798A JP3759312B2 (en) | 1997-08-28 | 1998-04-08 | Anticorrosion coating method for galvanized steel |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24786797 | 1997-08-28 | ||
| JP9-247867 | 1997-08-28 | ||
| JP11270798A JP3759312B2 (en) | 1997-08-28 | 1998-04-08 | Anticorrosion coating method for galvanized steel |
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| Publication Number | Publication Date |
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| JPH11131259A JPH11131259A (en) | 1999-05-18 |
| JP3759312B2 true JP3759312B2 (en) | 2006-03-22 |
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| JP2002241668A (en) * | 2001-02-14 | 2002-08-28 | Sumitomo Seika Chem Co Ltd | Polyethylene-based resin powder coating |
| JPWO2017068658A1 (en) * | 2015-10-21 | 2018-08-09 | 株式会社ハイテム | Method for manufacturing lattice member for poultry house cage and lattice member |
| CN112742682A (en) * | 2019-10-29 | 2021-05-04 | 西藏中驰集团股份有限公司 | Novel anticorrosive coating process |
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