JP6526406B2 - Method of passivating stainless steel parts and passivating solution for stainless steel parts - Google Patents
Method of passivating stainless steel parts and passivating solution for stainless steel parts Download PDFInfo
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- JP6526406B2 JP6526406B2 JP2014249683A JP2014249683A JP6526406B2 JP 6526406 B2 JP6526406 B2 JP 6526406B2 JP 2014249683 A JP2014249683 A JP 2014249683A JP 2014249683 A JP2014249683 A JP 2014249683A JP 6526406 B2 JP6526406 B2 JP 6526406B2
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- 229910001220 stainless steel Inorganic materials 0.000 title claims description 140
- 239000010935 stainless steel Substances 0.000 title claims description 134
- 238000000034 method Methods 0.000 title claims description 33
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 268
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 66
- 238000002161 passivation Methods 0.000 claims description 56
- 239000007788 liquid Substances 0.000 claims description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 20
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 16
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 16
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 16
- 150000001875 compounds Chemical class 0.000 claims description 8
- 239000001814 pectin Substances 0.000 claims description 7
- 229920001277 pectin Polymers 0.000 claims description 7
- 235000010987 pectin Nutrition 0.000 claims description 7
- 239000000230 xanthan gum Substances 0.000 claims description 7
- 229920001285 xanthan gum Polymers 0.000 claims description 7
- 229940082509 xanthan gum Drugs 0.000 claims description 7
- 235000010493 xanthan gum Nutrition 0.000 claims description 7
- 239000000243 solution Substances 0.000 description 92
- 229960004106 citric acid Drugs 0.000 description 81
- 230000007797 corrosion Effects 0.000 description 41
- 238000005260 corrosion Methods 0.000 description 41
- 238000012360 testing method Methods 0.000 description 30
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 29
- 239000011651 chromium Substances 0.000 description 22
- 239000002562 thickening agent Substances 0.000 description 20
- 230000000052 comparative effect Effects 0.000 description 19
- 229940105329 carboxymethylcellulose Drugs 0.000 description 12
- 229910052742 iron Inorganic materials 0.000 description 12
- 229910052804 chromium Inorganic materials 0.000 description 11
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 9
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 6
- 150000003839 salts Chemical class 0.000 description 6
- 239000007921 spray Substances 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- -1 iron ion Chemical class 0.000 description 5
- 238000005498 polishing Methods 0.000 description 5
- 238000001363 water suppression through gradient tailored excitation Methods 0.000 description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 4
- 230000002378 acidificating effect Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 4
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 4
- 238000005554 pickling Methods 0.000 description 4
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 4
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 4
- 229960004543 anhydrous citric acid Drugs 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 238000007654 immersion Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000000682 scanning probe acoustic microscopy Methods 0.000 description 3
- 239000013535 sea water Substances 0.000 description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229920003123 carboxymethyl cellulose sodium Polymers 0.000 description 2
- 229940063834 carboxymethylcellulose sodium Drugs 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- QOSATHPSBFQAML-UHFFFAOYSA-N hydrogen peroxide;hydrate Chemical compound O.OO QOSATHPSBFQAML-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000003672 processing method Methods 0.000 description 2
- 238000004611 spectroscopical analysis Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910017060 Fe Cr Inorganic materials 0.000 description 1
- 229910002544 Fe-Cr Inorganic materials 0.000 description 1
- 229910017315 Mo—Cu Inorganic materials 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 229910003286 Ni-Mn Inorganic materials 0.000 description 1
- 229910003296 Ni-Mo Inorganic materials 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 1
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
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- 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 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910001105 martensitic stainless steel Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000001139 pH measurement Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 229960000292 pectin Drugs 0.000 description 1
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- 229920006395 saturated elastomer Polymers 0.000 description 1
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- 238000003756 stirring Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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- Chemical Treatment Of Metals (AREA)
Description
本発明は、ステンレス鋼部品の不動態化処理方法及びステンレス鋼部品用の不動態化処理液に係り、特に、水門等のステンレス鋼部品の不動態化処理方法及びステンレス鋼部品用の不動態化処理液に関する。 The present invention relates to a method of passivating stainless steel parts and a passivating solution for stainless steel parts, and in particular, a passivating method of stainless steel parts such as water gates and the like and a passivating method for stainless steel parts It relates to a treatment liquid.
水門、圧縮機等に用いられるインペラ、原子力設備部品等のステンレス鋼部品の製造工程において、溶接・切断・研磨などの加工によりステンレス鋼部品の耐食性を担う不動態皮膜が除去されることから、一般的に組み立て後には不動態化処理が行われている。ステンレス鋼部品の不動態化処理方法としては、過酸化水素、硝酸、フッ酸、クロム酸などの酸性水溶液に浸漬させる方法、これらの酸性水溶液を塗布する方法、もしくは酸性およびアルカリ性水溶液でアノード電解させる方法などが提案されている。 In the manufacturing process of stainless steel parts such as water gates, compressors, etc., and stainless steel parts such as nuclear equipment parts, the passive film responsible for corrosion resistance of stainless steel parts is removed by processing such as welding, cutting and polishing. The passivation process is performed after assembly. As a method of passivation treatment of stainless steel parts, a method of immersing in an acidic aqueous solution of hydrogen peroxide, nitric acid, hydrofluoric acid, chromic acid, etc., a method of applying these acidic aqueous solutions, or anodic electrolysis with acidic and alkaline aqueous solutions Methods have been proposed.
特許文献１には、中性塩電解質濃度が０．１％以上５％以下で、過酸化水素濃度が０．１％以上１％以下含有する溶液を液膜状態に塗布し水洗するステンレス鋼の不動態化処理方法が記載されている。 Patent Document 1 discloses a stainless steel in which a solution containing a neutral salt electrolyte concentration of 0.1% to 5% and a hydrogen peroxide concentration of 0.1% to 1% is applied in a liquid film state and washed with water. A passivation treatment method is described.
ところで、ステンレス鋼部品を過酸化水素や硝酸等の酸性水溶液に浸漬等させるだけでは、ステンレス鋼部品の表面に十分な耐食性を有する不動態皮膜を形成できない可能性がある。また、塩害が生じやすい環境で使用される水門等のステンレス鋼部品では、より一層の耐食性が要求される場合がある。 By the way, just by immersing stainless steel parts in an acidic aqueous solution such as hydrogen peroxide or nitric acid, there is a possibility that a passive film having sufficient corrosion resistance can not be formed on the surface of stainless steel parts. Further, in the case of stainless steel parts such as water gates used in an environment susceptible to salt damage, even higher corrosion resistance may be required.
そこで本発明の目的は、より耐食性を向上させた不動態皮膜を形成可能なステンレス鋼部品の不動態化処理方法及びステンレス鋼部品用の不動態化処理液を提供することである。 Therefore, an object of the present invention is to provide a method for passivating a stainless steel component capable of forming a passivation film with further improved corrosion resistance, and a passivating solution for stainless steel component.
本発明に係るステンレス鋼部品の不動態化処理方法は、前記ステンレス鋼部品に、１質量％の過酸化水素と、前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満のクエン酸と、を含有し、残部が水からなる不動態化処理液を塗布または浸漬して不動態化処理する不動態化処理工程を備えることを特徴とする。 In the method for passivating a stainless steel component according to the present invention, the mass ratio of hydrogen peroxide of 1% by mass to the stainless steel component and the depassivated pH of stainless steel forming the stainless steel component is less than the mass ratio And a passivating treatment step of passivating treatment by applying or immersing a passivating treatment solution containing the balance with water.
本発明に係るステンレス鋼部品の不動態化処理方法は、前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨが２．５未満であり、前記不動態化処理液は、クエン酸の含有率が、０．１質量％以上であり、前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満であることを特徴とする。 The passivation treatment method for stainless steel parts according to the present invention is characterized in that the depassivation pH of stainless steel forming the stainless steel parts is less than 2.5, and the passivation treatment liquid contains citric acid. The ratio is 0.1 mass% or more, and is less than the mass ratio at which the depassivated pH of the stainless steel forming the stainless steel part is obtained.
本発明に係るステンレス鋼部品の不動態化処理方法において、前記不動態化処理液は、クエン酸の含有率が、０．１質量％以上１質量％以下であることを特徴とする。 In the passivation treatment method for stainless steel parts according to the present invention, the passivation treatment liquid is characterized in that the content of citric acid is 0.1% by mass or more and 1% by mass or less.
本発明に係るステンレス鋼部品の不動態化処理方法は、前記不動態化処理液は、残部の水の一部に代えて、カルボキシメチルセルロース、カルボキシメチルセルロース化合物、キサンタンガムまたはペクチンを含有することを特徴とする。 The method for passivating a stainless steel part according to the present invention is characterized in that the passivating solution contains carboxymethylcellulose, a carboxymethylcellulose compound, xanthan gum or pectin in place of a part of the remaining water. Do.
本発明に係るステンレス鋼部品用の不動態化処理液は、１質量％の過酸化水素と、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満のクエン酸と、を含有し、残部が水からなることを特徴とする。 The passivation treatment liquid for stainless steel parts according to the present invention comprises 1% by mass of hydrogen peroxide and citric acid less than the mass ratio at which the depassivated pH of stainless steel forming the stainless steel parts is obtained. It is characterized in that it contains and the remainder consists of water.
本発明に係るステンレス鋼部品用の不動態化処理液は、前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨが２．５未満であり、クエン酸の含有率が、０．１質量％以上であり、前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満であることを特徴とする。 In the passivating solution for stainless steel parts according to the present invention, the depassivation pH of the stainless steel forming the stainless steel parts is less than 2.5, and the content of citric acid is 0.1 mass % Or more and is less than the mass ratio at which the depassivated pH of the stainless steel forming the stainless steel part is achieved.
本発明に係るステンレス鋼部品用の不動態化処理液は、クエン酸の含有率が、０．１質量％以上１質量％以下であることを特徴とする。 The passivating solution for stainless steel parts according to the present invention is characterized in that the content of citric acid is 0.1% by mass or more and 1% by mass or less.
本発明に係るステンレス鋼部品用の不動態化処理液は、残部の水の一部に代えて、カルボキシメチルセルロース、カルボキシメチルセルロース化合物、キサンタンガムまたはペクチンを含有することを特徴とする。 The passivating solution for stainless steel parts according to the present invention is characterized in that it contains carboxymethylcellulose, a carboxymethylcellulose compound, xanthan gum or pectin in place of a part of the remaining water.
上記構成によれば、ステンレス鋼部品を不動態化処理するための不動態化処理液中に含まれるクエン酸が、不動態皮膜の形成時に、不動態皮膜中に含まれる鉄（Ｆｅ）分（鉄イオン）と錯体を形成することで、鉄分が溶解、除去されて、不動態皮膜中のクロム（Ｃｒ）濃度が高くなる。また、不動態化処理液には、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満のクエン酸を含有していることから、不動態化処理液のｐＨがステンレス鋼の脱不動態化ｐＨより高くなるので、安定した不動態皮膜を形成することができる。これにより、ステンレス鋼部品に形成された不動態皮膜の耐食性をより向上させることが可能となる。 According to the above configuration, the citric acid contained in the passivating solution for passivating stainless steel parts is a component of iron (Fe) contained in the passivating film when the passivating film is formed. By forming a complex with iron ion, iron is dissolved and removed to increase the chromium (Cr) concentration in the passive film. In addition, since the passivating solution contains citric acid less than the mass ratio at which the passivating pH of the stainless steel forming the stainless steel part becomes, the pH of the passivating solution is stainless steel. Because the pH is higher than the depassivated pH, a stable passive film can be formed. This makes it possible to further improve the corrosion resistance of the passive film formed on the stainless steel component.
以下に本発明の実施の形態について図面を用いて詳細に説明する。図１は、ステンレス鋼部品の不動態化処理方法の構成を示すフローチャートである。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a flow chart showing the configuration of a passivation processing method of stainless steel parts.
前処理工程（Ｓ１０）は、ステンレス鋼部品の表面の自然酸化皮膜を除去する工程である。ステンレス鋼部品に不動態皮膜を形成する前に、ステンレス鋼部品の表面に自然発生的に形成された耐食性が低い自然酸化皮膜を除去することが好ましい。 The pretreatment step (S10) is a step of removing the natural oxide film on the surface of the stainless steel part. Prior to forming the passive film on the stainless steel component, it is preferable to remove the low corrosion resistance natural oxide film formed spontaneously on the surface of the stainless steel component.
ステンレス鋼部品の前処理には、硝フッ酸溶液等を使用した酸洗処理や、機械研磨等の研磨が用いられる。ステンレス鋼部品の表面を研磨することにより、自然酸化皮膜の除去と共に、溶接や切断等の加工で形成された加工面をより平滑化することができる。ステンレス鋼部品の前処理として、脱脂洗浄処理を合わせて行うことが好ましい。ステンレス鋼部品の酸洗処理、脱脂洗浄処理、研磨については、一般的な金属材料の前処理に用いられる方法が適用可能である。 For pretreatment of stainless steel parts, pickling using a nitric hydrofluoric acid solution or the like, or polishing such as mechanical polishing is used. By polishing the surface of the stainless steel part, together with the removal of the natural oxide film, it is possible to further smooth the processed surface formed by processing such as welding or cutting. As a pretreatment of stainless steel parts, it is preferable to carry out degreasing and cleaning treatment in combination. For the pickling treatment of stainless steel parts, the degreasing cleaning treatment, and the polishing, methods used for general pretreatment of metal materials are applicable.
ステンレス鋼部品は、オーステナイト系ステンレス鋼、フェライト系ステンレス鋼、オーステナイト・フェライト系ステンレス鋼、マルテンサイト系ステンレス鋼、析出硬化型ステンレス鋼等で形成されている。これらのステンレス鋼は、Ｆｅ−Ｃｒ系合金、Ｆｅ−Ｃｒ−Ｎｉ系合金、Ｆｅ−Ｃｒ−Ｎｉ−Ｍｏ系合金、Ｆｅ−Ｃｒ−Ｎｉ−Ｍｏ―Ｃｕ系合金、Ｆｅ−Ｃｒ−Ｎｉ−Ｍｎ系合金等からなり、例えば、クロム（Ｃｒ）を１２質量％以上含有しているＦｅ系合金である。ステンレス鋼部品としては、例えば、水門、圧縮機等に用いられるインペラ、原子力設備部品等がある。 The stainless steel parts are formed of austenitic stainless steel, ferritic stainless steel, austenite / ferritic stainless steel, martensitic stainless steel, precipitation hardened stainless steel or the like. These stainless steels include Fe-Cr alloys, Fe-Cr-Ni alloys, Fe-Cr-Ni-Mo alloys, Fe-Cr-Ni-Mo-Cu alloys, Fe-Cr-Ni-Mn alloys. It is an Fe-based alloy made of an alloy or the like and containing, for example, 12% by mass or more of chromium (Cr). As stainless steel parts, there are, for example, water gates, impellers used for compressors, etc., nuclear equipment parts, etc.
不動態化処理工程（Ｓ１２）は、ステンレス鋼部品に、１質量％の過酸化水素と、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満のクエン酸と、を含有し、残部が水からなる不動態化処理液を塗布または浸漬して不動態化処理する工程である。 The passivation treatment step (S12) contains, in the stainless steel part, 1% by mass of hydrogen peroxide and citric acid which is less than the mass ratio at which the depassivated pH of the stainless steel forming the stainless steel part is obtained. And passivating treatment by applying or immersing a passivating treatment solution of which the remainder is water.
まず、ステンレス鋼部品用の不動態化処理液について説明する。不動態化処理液は、１質量％の過酸化水素と、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満のクエン酸と、を含有し、残部が水から構成されている。 First, a passivation treatment solution for stainless steel parts will be described. The passivating solution contains 1% by weight of hydrogen peroxide and citric acid which is less than the mass ratio to achieve the passivating pH of stainless steel forming the stainless steel part, and the balance is composed of water. ing.
過酸化水素は、ステンレス鋼部品の表面に不動態皮膜を形成するための酸化剤としての機能を有している。過酸化水素は、時間の経過に伴って水と酸素とに分解するので、環境負荷を低減することができる。不動態化処理液には、過酸化水素が１質量％含有されている。過酸化水素の含有率が１質量％より低い場合には、酸化力が弱くなるので不動態皮膜を形成し難くなるからである。また、過酸化水素の含有率が１質量％であれば、安定した不動態皮膜の形成が可能だからである。過酸化水素については、一般的に市販されているものを用いることができる。 Hydrogen peroxide has a function as an oxidizing agent for forming a passive film on the surface of stainless steel parts. Since hydrogen peroxide decomposes into water and oxygen over time, environmental impact can be reduced. The passivating solution contains 1% by mass of hydrogen peroxide. If the content of hydrogen peroxide is less than 1% by mass, the oxidizing power is weak, and it is difficult to form a passive film. In addition, if the hydrogen peroxide content is 1% by mass, it is possible to form a stable passive film. As hydrogen peroxide, those generally marketed can be used.
クエン酸は、不動態皮膜の形成時に、不動態皮膜中に含まれる鉄（Ｆｅ）分（鉄イオン）と錯体を形成することにより、鉄分が溶解、除去されて、不動態皮膜中に含まれるクロム（Ｃｒ）分を濃縮する機能を有している。これにより不動態皮膜中のクロム濃度が高くなるので、不動態皮膜の耐食性をより向上させることが可能となる。クエン酸は、食品等にも用いられている弱酸であるため、環境負荷を低減することが可能となる。クエン酸には、一般的に市販されている無水クエン酸やクエン酸水和物等を用いることが可能である。 Citric acid is included in the passivation film by forming a complex with iron (Fe) (iron ion) contained in the passivation film at the time of formation of the passivation film, whereby the iron content is dissolved and removed. It has a function to concentrate chromium (Cr) content. Since the chromium concentration in a passive film becomes high by this, it becomes possible to improve corrosion resistance of a passive film more. Citric acid is a weak acid which is also used in food and the like, and therefore, environmental impact can be reduced. As citric acid, it is possible to use generally commercially available anhydrous citric acid, citric acid hydrate and the like.
クエン酸の含有率については、０質量％より大きく、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満となるように、不動態化処理液が調製される。クエン酸の含有率を、ステンレス鋼の脱不動態化ｐＨとなる質量比未満とするのは、クエン酸の含有率を、ステンレス鋼の脱不動態化ｐＨとなる質量比以上とすると、不動態化処理液のｐＨがステンレス鋼の脱不動態化ｐＨ以下となるので（より酸性が強くなるので）、ステンレス鋼の脱不動態化が生じることにより、不動態皮膜の形成が阻害される可能性があるからである。 The passivating solution is prepared such that the content of citric acid is greater than 0% by mass and less than the mass ratio at which the depassivated pH of the stainless steel forming the stainless steel part is achieved. The content of citric acid is less than the mass ratio that results in the depassivated pH of stainless steel because the content of citric acid is equal to or higher than the mass ratio that results in the depassivated pH of stainless steel. Since the pH of the solution is below the depassivation pH of stainless steel (as the acidity becomes stronger), the depassivation of stainless steel may inhibit the formation of a passivation film. Because there is
ステンレス鋼の脱不動態化ｐＨについてより詳細に説明する。ステンレス鋼の脱不動態化ｐＨとは、ステンレス鋼が耐食性を示せなくなるｐＨ値のことである。ステンレス鋼は、脱不動態化ｐＨ以下の溶液（酸性がより強くなる溶液）では、安定した不動態皮膜が形成されず、良好な耐食性を示すことが難しくなる。ステンレス鋼の脱不動態化ｐＨは、各種ステンレス鋼ごとに求められている。ステンレス鋼の脱不動態化ｐＨは、Ｃｒ、Ｍｏ等の含有率が大きくなるほど低くなる傾向があり、これらの元素の含有率が小さくなるほど高くなる傾向がある。例えば、ＳＵＳ３０４の脱不動態化ｐＨは約２．０であり、ＳＵＳ３１６の脱不動態化ｐＨは約１．５である。このため、ＳＵＳ３０４の場合には、不動態化処理液のｐＨが２．０以下になると脱不動態化しやすくなり、ＳＵＳ３１６の場合には、不動態化処理液のｐＨが１．５以下になると脱不動態化しやすくなる。 The depassivation pH of stainless steel is described in more detail. The depassivated pH of stainless steel is the pH value at which stainless steel does not exhibit corrosion resistance. Stainless steel does not form a stable passivation film in a solution below the depassivation pH (a solution in which the acidity becomes stronger), making it difficult to exhibit good corrosion resistance. The depassivation pH of stainless steel is determined for each of the various stainless steels. The depassivation pH of stainless steel tends to decrease as the content of Cr, Mo and the like increases, and tends to increase as the content of these elements decreases. For example, the depassivated pH of SUS304 is about 2.0 and the passivated pH of SUS316 is about 1.5. For this reason, in the case of SUS304, it becomes easy to be depassivated when the pH of the passivating solution becomes 2.0 or less, and in the case of SUS316, the pH becomes 1.5 or less. It becomes easy to depassivate.
ステンレス鋼の脱不動態化ｐＨについては、文献値を用いてもよく、実験等で測定してもよい。図２は、各種ステンレス鋼の脱不動態化ｐＨを示す図である。図２については、（社）腐食防食協会「ステンレス鋼の特性と使用上の要点」（２０１２）Ｐ１０から引用している。 For the depassivation pH of stainless steel, a literature value may be used, or it may be measured by experiment or the like. FIG. 2 is a diagram showing the depassivation pH of various stainless steels. As for FIG. 2, the corrosion and corrosion protection association "characteristics and usage points of stainless steel" (2012) is quoted from P10.
ステンレス鋼の脱不動態化ｐＨを実験等で測定する場合には、例えば、室温でｐＨを変えた硫酸溶液等の酸性溶液に、自然酸化皮膜を除去したステンレス鋼を浸漬して浸漬電位を測定し、ステンレス鋼の不動態化による浸漬電位の上昇が認められないｐＨの中で、最も大きなｐＨ値を脱不動態化ｐＨとすればよい。 When measuring the depassivation pH of stainless steel by experiments etc., for example, the immersion potential is measured by immersing the stainless steel from which the natural oxide film has been removed in an acidic solution such as a sulfuric acid solution whose pH is changed at room temperature. Among the pH at which the rise in immersion potential due to the passivation of stainless steel is not observed, the largest pH value may be taken as the depassivation pH.
不動態化処理液のｐＨは、後述する実施例で示すように、クエン酸の含有率により変化する。クエン酸の含有率が小さいほどｐＨは高くなり、クエン酸の含有率が大きいほどｐＨは低くなる。より詳細には、後述する実施例の図３のグラフに示すように、１質量％の過酸化水素を含む不動態化処理液において、不動態化処理液のｐＨ（室温）は、クエン酸を含まない場合が６．２であり、クエン酸０．１質量％の場合が３．１であり、クエン酸１質量％の場合が２．５であり、クエン酸５質量％の場合が２．１であり、クエン酸１０質量％の場合が１．９となる。不動態化処理液のｐＨと、クエン酸の含有率との関係については、予め実験等で求めておくとよい。 The pH of the passivating solution changes depending on the content of citric acid, as shown in the examples described later. The lower the citric acid content, the higher the pH, and the higher the citric acid content, the lower the pH. More specifically, as shown in the graph of FIG. 3 of the example described later, in the passivating solution containing 1% by mass of hydrogen peroxide, the pH (room temperature) of the passivating solution is citric acid. The case where it does not contain is 6.2, the case of 0.1 mass% of citric acid is 3.1, the case of 1 mass% of citric acid is 2.5, and the case of 5 mass% of citric acid is 2. It is 1, and it becomes 1.9 in the case of 10 mass% of citric acid. The relationship between the pH of the passivating solution and the content of citric acid may be obtained in advance by experiments or the like.
ステンレス鋼の脱不動態化ｐＨが２．５未満である場合には、１質量％の過酸化水素を含む不動態化処理液において、クエン酸の含有率は、０．１質量％以上であり、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満となるように調製されることが好ましい。 When the depassivation pH of stainless steel is less than 2.5, the content of citric acid is 0.1% by mass or more in the passivating solution containing 1% by mass of hydrogen peroxide. Preferably, it is prepared to be less than the mass ratio at which the depassivated pH of stainless steel forming the stainless steel part is achieved.
水門、圧縮機等に用いられるインペラ、原子力設備部品等のステンレス鋼部品は、主に、ＳＵＳ３０４、ＳＵＳ３１６、ＳＵＳ６３０等の脱不動態化ｐＨが２．５未満であるステンレス鋼で形成されている。このようなステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨが２．５未満である場合には、１質量％の過酸化水素を含む不動態化処理液において、クエン酸の含有率が、０．１質量％以上であり、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満となるように調製することにより、不動態皮膜における耐海水腐食性や耐孔食性等の耐食性を向上させることが可能となる。 Stainless steel parts such as water gates, impellers used for compressors, etc., nuclear equipment parts, etc. are mainly formed of stainless steel such as SUS304, SUS316, SUS630, etc. having a depassivation pH of less than 2.5. When the depassivation pH of the stainless steel forming such stainless steel parts is less than 2.5, the content of citric acid in the passivating solution containing 1% by mass of hydrogen peroxide is The corrosion resistance to seawater and pitting corrosion in the passivation film is adjusted to be less than the mass ratio that is 0.1% by mass or more and the depassivated pH of the stainless steel forming the stainless steel part. It is possible to improve the corrosion resistance such as
例えば、ステンレス鋼にＳＵＳ６３０を用いた場合には、ＳＵＳ６３０の脱不動態化ｐＨが約２．４であるので、クエン酸の含有率が、０．１質量％以上であり、ＳＵＳ６３０の脱不動態化ｐＨ２．４となる質量比未満となるように、不動態化処理液を調製することが好ましい。ＳＵＳ６３０の脱不動態化ｐＨ２．４となるクエン酸の含有率については、後述する実施例の図３のグラフに示すように２質量％であるので、１質量％の過酸化水素を含む不動態化処理液に含まれるクエン酸の含有率は、０．１質量％以上２質量％未満とするとよい。これにより、不動態化処理液のｐＨが、ＳＵＳ６３０の脱不動態化ｐＨ２．４より高くなるので、安定した不動態皮膜を形成可能になる。 For example, when SUS630 is used for stainless steel, since the depassivated pH of SUS630 is about 2.4, the content of citric acid is 0.1% by mass or more, and the SUS630 depassivation is performed. It is preferable to prepare the passivation treatment liquid so as to be less than the mass ratio at which the conversion pH is 2.4. The content ratio of citric acid to be depassivated pH 2.4 of SUS630 is 2% by mass as shown in the graph of FIG. 3 of the example described later, so the passivity including 1% by mass of hydrogen peroxide The content of citric acid contained in the chemical treatment solution may be 0.1% by mass or more and less than 2% by mass. As a result, the pH of the passivating solution becomes higher than the depassivated pH 2.4 of SUS630, so that a stable passivated film can be formed.
ステンレス鋼の脱不動態化ｐＨが２．５未満である場合には、１質量％の過酸化水素を含む不動態化処理液において、クエン酸の含有率は、０．１質量％以上１質量％以下となるように調製されることが好ましい。後述する実施例の図３のグラフに示すように、クエン酸の含有率が０．１質量％の場合には、不動態化処理液のｐＨが３．１となり、クエン酸の含有率が１質量％の場合には、不動態化処理液のｐＨが２．５となる。これにより、脱不動態化ｐＨが２．５未満のいずれのステンレス鋼においても、不動態化処理液を適用可能となることから、ステンレス鋼の種類ごとに不動態化処理液を調製する必要がないので、生産性を向上させることが可能となる。 When the depassivation pH of stainless steel is less than 2.5, the content of citric acid is 0.1% by mass or more in a passivating solution containing 1% by mass of hydrogen peroxide. It is preferable to prepare so that it becomes less than%. As shown in the graph of FIG. 3 of the example described later, when the content of citric acid is 0.1% by mass, the pH of the passivation treatment solution is 3.1, and the content of citric acid is 1 In the case of mass%, the pH of the passivation treatment solution is 2.5. As a result, the passivation treatment solution can be applied to any stainless steel having a depassivation pH of less than 2.5, so it is necessary to prepare a passivation treatment solution for each type of stainless steel. Because it does not exist, it becomes possible to improve productivity.
不動態化処理液に含まれる水については、溶媒としての機能を有しており、一般的な水道水や脱イオン水等を用いることが可能である。 The water contained in the passivating solution has a function as a solvent, and general tap water, deionized water or the like can be used.
不動態化処理液には、残部の水の一部に代えて、増粘剤を含有するようにしてもよい。不動態化処理液に増粘剤を含有させることにより、不動態化処理液が増粘されて、例えば、ゲル状やペースト状になる。その結果、不動態化処理液の密着性が高くなりステンレス鋼部品の表面に不動態化処理液が保持され易くなることから、不動態化処理液の弾きと流動とが抑えられるので塗布作業性が向上する。また、ステンレス鋼部品の表面に不動態化処理液が保持され易くなることから、ステンレス鋼部品の表面に耐食性をより向上させた不動態皮膜を形成可能となる。例えば、大型のステンレス鋼部品や、ステンレス鋼部品の表面に非水平面（垂直面、傾斜面、曲面等）を含む場合でも、不動態化処理液が増粘されて粘性が高くなっているので、不動態化処理液の弾きや流動を抑制することができる。 The passivating solution may contain a thickener in place of a part of the remaining water. By including a thickener in the passivating treatment solution, the passivating treatment solution is thickened to be, for example, gel or paste. As a result, the adhesion of the passivating solution becomes high, and the passivating solution is easily held on the surface of the stainless steel part, so that the repulsion and flow of the passivating solution can be suppressed, so that the coating workability can be achieved. Improve. In addition, since the passivation treatment liquid is easily held on the surface of the stainless steel part, it is possible to form a passivation film on the surface of the stainless steel part with further improved corrosion resistance. For example, even when the surface of a large stainless steel part or a stainless steel part includes non-horizontal surfaces (vertical surface, inclined surface, curved surface, etc.), the passivating solution is thickened to increase viscosity, It is possible to suppress the repelling and flow of the passivating treatment solution.
増粘剤には、カルボキシメチルセルロース、カルボキシメチルセルロースナトリウム等のカルボキシメチルセルロース化合物、キサンタンガムまたはペクチン、水溶性レジン等を用いることが可能である。増粘剤には、カルボキシメチルセルロース、カルボキシメチルセルロース化合物、キサンタンガムまたはペクチンを用いることが好ましい。これらの増粘剤は、過酸化水素における水と酸素とへの分解を抑制可能であると共に、増粘剤自身が過酸化水素により分解され難いからである。また、これらの増粘剤については、不動態化処理液のｐＨに殆ど影響を与えないので、不動態化処理液に添加してもｐＨの変化を抑制することができる。増粘剤については、これらの増粘剤を単独で用いてもよいし、複数の増粘剤を組み合わせて用いてもよい。なお、増粘剤には、カルボキシメチルセルロースまたはカルボキシメチルセルロース化合物を用いることがより好ましい。カルボキシメチルセルロースやカルボキシメチルセルロース化合物は、キサンタンガムやペクチン等よりも安価であるため、製造コストを低減することが可能となる。 As the thickener, it is possible to use carboxymethylcellulose, a carboxymethylcellulose compound such as carboxymethylcellulose sodium, xanthan gum or pectin, a water-soluble resin or the like. As the thickener, it is preferable to use carboxymethylcellulose, a carboxymethylcellulose compound, xanthan gum or pectin. These thickeners can suppress the decomposition of hydrogen peroxide into water and oxygen, and the thickener itself is difficult to be decomposed by hydrogen peroxide. In addition, since these thickeners hardly affect the pH of the passivating treatment solution, the pH change can be suppressed even when added to the passivating treatment solution. As the thickener, these thickeners may be used alone, or a plurality of thickeners may be used in combination. In addition, it is more preferable to use a carboxymethylcellulose or a carboxymethylcellulose compound as a thickener. Since carboxymethylcellulose and carboxymethylcellulose compounds are less expensive than xanthan gum, pectin and the like, the manufacturing cost can be reduced.
増粘剤の含有率は、０質量％よりも大きく１０質量％以下であることが好ましく、０質量％よりも大きく５質量％以下であることがより好ましい。増粘剤の含有率が１０質量％より多いと、不動態化処理液の粘度が高くなることから、ステンレス鋼部品の表面に不動態化処理液を塗布または浸漬し難くなるからである。 The content of the thickener is preferably more than 0% by mass and 10% by mass or less, and more preferably more than 0% by mass and 5% by mass or less. If the content of the thickener is more than 10% by mass, the viscosity of the passivating treatment solution becomes high, which makes it difficult to apply or immerse the passivating treatment solution on the surface of the stainless steel part.
次に、不動態化処理液の作製方法について説明する。不動態化処理液については、例えば、過酸化水素水にクエン酸を溶解して作製することができる。不動態化処理液に増粘剤を含有させる場合には、過酸化水素水に増粘剤を添加して過酸化水素水ゲルを作製した後、クエン酸を溶解させて作製してもよいし、過酸化水素水にクエン酸を溶解した後に、増粘剤を添加してゲル状にしてもよい。また、水にクエン酸を溶解し、増粘剤を添加してクエン酸ゲルを作製した後に、過酸化水素水を添加して作製してもよい。更に、増粘剤を水に溶解させた後に過酸化水素水と混合して過酸化水素水ゲルとし、この過酸化水素水ゲルにクエン酸を溶解させてもよい。なお、ミキサや超音波装置等を用いて混合撹拌することにより、より均一な不動態化処理液を作製することができる。 Next, a method of producing a passivation treatment liquid will be described. The passivating solution can be produced, for example, by dissolving citric acid in hydrogen peroxide water. When a passivating solution contains a thickener, it may be prepared by dissolving a citric acid after adding a thickener to a hydrogen peroxide solution to prepare a hydrogen peroxide solution gel. After dissolving citric acid in hydrogen peroxide solution, a thickener may be added to make it gel. Alternatively, after citric acid is dissolved in water and a thickener is added to prepare a citric acid gel, hydrogen peroxide solution may be added to make the gel. Further, the thickener may be dissolved in water and then mixed with a hydrogen peroxide solution to form a hydrogen peroxide solution gel, and citric acid may be dissolved in the hydrogen peroxide solution gel. A more uniform passivation treatment solution can be produced by mixing and stirring using a mixer, an ultrasonic device or the like.
次に、ステンレス鋼部品に不動態化処理液を塗布または浸漬する方法について説明する。不動態化処理液の塗布方法については、刷毛塗り、へら塗り、ローラ塗り、スプレーによる噴射等の一般的な塗布方法が適用可能である。塗装手段や塗装装置についても、塗料等の塗布に用いられる一般的な刷毛、へら、ローラ、スプレーガン等を用いることができる。ステンレス鋼部品を不動態化処理液に浸漬する場合には、不動態化処理液を入れた容器にステンレス鋼部品を入れて浸漬させる等の一般的な浸漬方法が適用可能である。 Next, a method of applying or immersing a passivation treatment liquid to a stainless steel part will be described. As a method of applying the passivating treatment liquid, general application methods such as brush coating, spatula coating, roller coating, spray spraying and the like can be applied. Also for the coating means and the coating apparatus, a general brush, a spatula, a roller, a spray gun or the like used for applying a paint or the like can be used. In the case of immersing stainless steel parts in a passivation treatment liquid, a general immersion method such as putting the stainless steel parts in a container containing the passivation treatment liquid and immersing is applicable.
不動態化処理液の液温については、特に限定されないが、常温（２０℃から３０℃）であることが好ましい。不動態化処理液を加熱するためのヒータや液温管理等が不要になるので、製造コストを低減することができる。また、不動態皮膜にはクロムが濃化されているので、常温の不動態化処理液で不動態化処理した場合でも十分な耐食性が得られるからである。ステンレス鋼部品に不動態化処理液を塗布または浸漬した後には、水洗や乾燥を行うようにしてもよい。このようにして、ステンレス鋼部品の表面に不動態皮膜が形成される。 The liquid temperature of the passivating treatment liquid is not particularly limited, but is preferably normal temperature (20 ° C. to 30 ° C.). Since a heater for heating the passivating treatment liquid, liquid temperature management, and the like become unnecessary, the manufacturing cost can be reduced. Further, since chromium is concentrated in the passivation film, sufficient corrosion resistance can be obtained even when passivation treatment is performed with a passivation treatment solution at normal temperature. After applying or immersing the passivating solution to the stainless steel parts, washing or drying may be performed. In this way, a passive film is formed on the surface of the stainless steel part.
以上、上記構成によれば、ステンレス鋼部品に、１質量％の過酸化水素と、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる質量比未満のクエン酸と、を含有し、残部が水からなる不動態化処理液を塗布または浸漬して不動態化処理する不動態化処理工程を備えていることから、不動態化処理液中に含まれるクエン酸が、不動態皮膜の形成時に、不動態皮膜中に含まれる鉄分（鉄イオン）と錯体を形成することで、鉄分が溶解、除去されて、不動態皮膜中のクロム濃度が高くなる。また、不動態化処理液のｐＨが、ステンレス鋼の脱不動態化ｐＨより大きくなることから、ステンレス鋼部品の表面に安定した不動態皮膜を形成することができる。これにより、ステンレス鋼部品に形成された不動態皮膜の耐食性をより向上させることが可能となる。 As described above, according to the above configuration, the stainless steel component contains 1% by mass of hydrogen peroxide and citric acid which is less than the mass ratio at which the depassivated pH of the stainless steel forming the stainless steel component becomes. Since it is equipped with a passivating treatment step of applying or immersing the passivating treatment solution of which the remainder is water, or applying and immersing, citric acid contained in the passivating treatment solution is a component of the passivating film. By forming a complex with iron (iron ion) contained in the passive film at the time of formation, the iron is dissolved and removed to increase the chromium concentration in the passive film. In addition, since the pH of the passivating solution becomes higher than the depassivating pH of stainless steel, a stable passivated film can be formed on the surface of stainless steel parts. This makes it possible to further improve the corrosion resistance of the passive film formed on the stainless steel component.
（不動態化処理液のｐＨとクエン酸の含有率との関係）
不動態化処理液のｐＨと、クエン酸の含有率との関係について評価した。過酸化水素水（昭和化学株式会社製、特級）に、クエン酸を０．１質量％、０．５質量％、１質量％、５質量％、１０質量％、２０質量％、３０質量％、４０質量％となるように各々溶解して不動態化処理液を作製した。クエン酸の最大含有率を４０質量％としたのは、室温（２０℃から３０℃）における水へのクエン酸の飽和溶解量が約４０質量％であるからである。クエン酸には、無水クエン酸（昭和化学株式会社製、１級）を用いた。各不動態化処理液における過酸化水素の含有率については、いずれも１質量％となるように調製した。不動態化処理液のｐＨ測定については、ｐＨメータを用いて室温（２０℃から３０℃）にて行った。なお、クエン酸を含まない１質量％過酸化水素を含有する不動態化処理液についてもｐＨ測定を行った。
(Relationship between pH of passivated solution and content of citric acid)
The relationship between the pH of the passivating solution and the content of citric acid was evaluated. 0.1% by mass, 0.5% by mass, 1% by mass, 5% by mass, 10% by mass, 20% by mass, 30% by mass of citric acid in hydrogen peroxide solution (manufactured by Showa Chemical Co., Ltd., special grade) Each was dissolved so as to be 40% by mass to prepare a passivation treatment solution. The reason why the maximum content of citric acid is 40% by mass is that the saturated dissolution amount of citric acid in water at room temperature (20 ° C. to 30 ° C.) is about 40% by mass. For citric acid, anhydrous citric acid (manufactured by Showa Chemical Co., Ltd., first grade) was used. The hydrogen peroxide content in each passivating solution was adjusted to 1% by mass. The pH of the passivating solution was measured at room temperature (20 ° C. to 30 ° C.) using a pH meter. In addition, pH measurement was performed also about the passivation process liquid containing 1 mass% hydrogen peroxide which does not contain a citric acid.
図３は、不動態化処理液のｐＨと、クエン酸の含有率との関係を示すグラフである。図３のグラフでは、横軸にクエン酸の含有率を取り、縦軸に不動態化処理液のｐＨを取り、不動態化処理液のｐＨを白菱形で示している。 FIG. 3 is a graph showing the relationship between the pH of the passivating solution and the content of citric acid. In the graph of FIG. 3, the abscissa represents the content of citric acid, the ordinate represents the pH of the passivating solution, and the pH of the passivating solution is indicated by open diamonds.
不動態化処理液のｐＨについては、６．２（クエン酸０質量％）、３．１（クエン酸０．１質量％）、２．６（クエン酸０．５質量％）、２．５（クエン酸１質量％）、２．１（クエン酸５質量％）、１．９（クエン酸１０質量％）、１．６（クエン酸２０質量％）、１．３（クエン酸３０質量％）、１．１（クエン酸４０質量％）であった。 The pH of the passivating solution is 6.2 (0 mass% citric acid), 3.1 (0.1 mass% citric acid), 2.6 (0.5 mass% citric acid), 2.5 (Citric acid 1% by mass), 2.1 (5% by mass citric acid), 1.9 (10% by mass citric acid), 1.6 (20% by mass citric acid), 1.3 (30% by mass citric acid) ), 1.1 (40% by mass of citric acid).
クエン酸の含有率が大きくなるほど不動態化処理液のｐＨが小さくなった（酸性がより強くなる）。また、不動態化処理液のｐＨについては、クエン酸の含有率が０質量％から１質量％までが不動態化処理液のｐＨの低下の度合いが大きく、クエン酸の含有率が１質量％以上では、不動態化処理液のｐＨが緩やかに低下した。 The higher the citric acid content, the lower the pH of the passivating solution (the acidity becomes stronger). In addition, with regard to the pH of the passivating treatment liquid, the content of citric acid is from 0% by mass to 1% by mass, the degree of decrease in pH of the passivating treatment liquid is large, and the content of citric acid is 1% by mass Above, the pH of the passivating solution gradually decreased.
（耐食性評価）
ステンレス鋼材に不動態化処理を行って耐食性を評価した。
(Evaluation of corrosion resistance)
The stainless steel was passivated to evaluate its corrosion resistance.
供試体には、ＳＵＳ６３０製のシート材を使用した。ＳＵＳ６３０の脱不動態化ｐＨは、約２．４である。供試体サイズについては、幅７０ｍｍ×長さ１５０ｍｍ×厚み３ｍｍｔとした。前処理については、供試体を酸洗処理して自然酸化皮膜を除去した。 The sheet material made from SUS630 was used for the specimen. The depassivation pH of SUS630 is about 2.4. The specimen size was width 70 mm × length 150 mm × thickness 3 mm t. For pretreatment, the sample was pickled to remove the natural oxide film.
次に、酸洗処理した供試体について、不動態化処理を行った。まず、不動態化処理液の調製について説明する。 Next, passivation treatment was performed on the pickled specimen. First, preparation of a passivation treatment solution will be described.
６０℃から８０℃程度の温水に、増粘剤であるカルボキシメチルセルロースナトリウム（昭和化学株式会社 １級）を添加し、十分に撹拌してカルボキシメチルセルロースナトリウム水溶液とした。次に、カルボキシメチルセルロースナトリウム水溶液と、過酸化水素水（昭和化学株式会社製、特級）とを混合撹拌して、過酸化水素水ゲルを調製した。次に、過酸化水素水ゲルに対して、所定量の無水クエン酸（昭和化学株式会社製、１級）を添加して混合撹拌し、０．１質量％、１質量％、５質量、２０質量％、４０質量％のクエン酸を含有する不動態化処理液を各々調製した。各不動態化処理液に対するカルボキシメチルセルロースナトリウムの含有率については、いずれも３質量％とし、過酸化水素の含有率については、いずれも１質量％とした。なお、クエン酸を含有せず、カルボキシメチルセルロースナトリウムを３質量％と、過酸化水素を１質量％と、を含有する不動態化処理液についても調製した。また、各不動態化処理液について室温（２０℃から３０℃）でｐＨ測定を行ったところ、図３に示す増粘剤を含まない各クエン酸含有率の不動態化処理液のｐＨと略同じであった。 Sodium carboxymethylcellulose (1st class Showa Chemical Co., Ltd.), which is a thickener, was added to warm water of about 60 ° C. to 80 ° C., and sufficiently stirred to obtain an aqueous solution of sodium carboxymethyl cellulose. Next, a sodium carboxymethylcellulose aqueous solution and a hydrogen peroxide solution (manufactured by Showa Chemical Co., Ltd., special grade) were mixed and stirred to prepare a hydrogen peroxide water gel. Next, a predetermined amount of anhydrous citric acid (manufactured by Showa Chemical Co., Ltd., 1st grade) is added to the hydrogen peroxide solution gel, and mixed and stirred to 0.1 mass%, 1 mass%, 5 mass, 20 A passivating solution containing 40% by weight of citric acid by weight was prepared. The content of sodium carboxymethylcellulose relative to each passivating solution was 3% by mass, and the content of hydrogen peroxide was 1% by mass. In addition, it prepared also about the passivation process liquid which does not contain a citric acid and contains 3 mass% of carboxymethylcellulose sodium and 1 mass% of hydrogen peroxide. In addition, when pH was measured at room temperature (20 ° C. to 30 ° C.) for each passivating treatment solution, the pH of the passivating treatment solution of each citric acid content not containing a thickener as shown in FIG. It was the same.
次に、酸洗処理した供試体の表面に、各不動態化処理液を刷毛塗りにて塗布した。不動態化処理液を塗布した状態で２時間保持し、その後、水洗した。 Next, each passivating treatment solution was applied by brushing on the surface of the pickled specimen. The passivating solution was kept for 2 hours while being applied, and then washed with water.
実施例１の供試体については、クエン酸を０．１質量％含有する不動態化処理液を用いた。実施例２の供試体については、クエン酸を１質量％含有する不動態化処理液を用いた。 For the specimen of Example 1, a passivating solution containing 0.1% by mass of citric acid was used. For the specimen of Example 2, a passivating solution containing 1% by mass of citric acid was used.
比較例１の供試体については、クエン酸を含有しない不動態化処理液（酸化剤が過酸化水素のみ）を用いた。比較例２の供試体については、クエン酸を５質量％含有する不動態化処理液を用いた。比較例３の供試体については、クエン酸を２０質量％含有する不動態化処理液を用いた。比較例４の供試体については、クエン酸を４０質量％含有する不動態化処理液を用いた。比較例５の供試体として、酸洗処理のみを行い、不動態化処理をしていないものを用意した。 For the test piece of Comparative Example 1, a passivating treatment solution containing only citric acid (the oxidizing agent was only hydrogen peroxide) was used. For the specimen of Comparative Example 2, a passivating solution containing 5% by mass of citric acid was used. For the specimen of Comparative Example 3, a passivating solution containing 20% by mass of citric acid was used. For the specimen of Comparative Example 4, a passivating solution containing 40% by mass of citric acid was used. As a test piece of Comparative Example 5, only pickling treatment was carried out, and one not subjected to passivation treatment was prepared.
次に、不動態化処理した供試体における耐海水腐食性、耐孔食性等の耐食性を評価するために、塩水噴霧試験（ＪＩＳ Ｚ ２３７１）と、塩化第二鉄腐食試験（ＪＩＳ Ｇ ０５７８）とを行った。 Next, a salt spray test (JIS Z 2371) and a ferric chloride corrosion test (JIS G 0578) are performed to evaluate the corrosion resistance such as seawater corrosion resistance and pitting corrosion resistance in the passivated specimen. Did.
まず、塩水噴霧試験の結果について説明する。図４は、塩水噴霧試験後の供試体の外観観察結果を示す写真である。供試体の外観観察については、試験前と、２４時間経過後と、１５０時間経過後について行った。なお、図４において、丸で囲まれた部分は腐食が生じた箇所を示している。図４に示すように、酸洗処理のみ行った比較例５の供試体や、クエン酸を含有しない不動態化処理液を用いた比較例１の供試体については、２４時間経過後に腐食が生じていた。 First, the results of the salt spray test will be described. FIG. 4: is a photograph which shows the external appearance observation result of the sample after a salt spray test. About the appearance observation of the specimen, it carried out about before test, after 24 hours, and after 150 hours. In FIG. 4, a circled portion indicates a portion where corrosion has occurred. As shown in FIG. 4, in the test piece of Comparative Example 5 in which only the pickling treatment was performed, and in the test piece of Comparative Example 1 using the passivating treatment solution containing no citric acid, corrosion occurred after 24 hours. It was
これに対して、クエン酸を０．１質量％、１質量％、５質量％、２０質量％含有する各不動態化処理液を用いた実施例１、２、比較例２、３の供試体については、１５０時間経過後においても腐食の発生が認められなかった。また、クエン酸を４０質量％含有する不動態化処理液を用いた比較例３の供試体については、１５０時間経過後において一部に腐食が認められた。 On the other hand, the test pieces of Examples 1 and 2 and Comparative Examples 2 and 3 using each passivating solution containing 0.1% by mass, 1% by mass, 5% by mass and 20% by mass citric acid. No corrosion was observed even after 150 hours. Moreover, about the sample of the comparative example 3 using the passivation process liquid containing a citric acid 40 mass%, corrosion was recognized in part after 150-hour progress.
次に、塩化第二鉄腐食試験の結果について説明する。図５は、塩化第二鉄腐食試験の試験結果を示すグラフである。図５のグラフでは、横軸に平均腐食速度を取り、各供試体の平均腐食速度を棒グラフで表わしている。図５に示すように、クエン酸を０．１質量％、１質量％含有する各不動態化処理液を用いた実施例１、２の供試体については、他の不動態化処理液を用いた供試体よりも平均腐食速度が小さく、最も耐食性に優れていた。これに対して、クエン酸を５質量％、２０質量％、４０質量％含有する各不動態化処理液を用いた比較例２、３、４の供試体については、クエン酸を含まない不動態化処理液を用いた比較例１の供試体よりも平均腐食速度が大きくなり、耐食性が低下した。 Next, the results of the ferric chloride corrosion test will be described. FIG. 5 is a graph showing the test results of the ferric chloride corrosion test. In the graph of FIG. 5, the horizontal axis is the average corrosion rate, and the average corrosion rate of each specimen is represented by a bar graph. As shown in FIG. 5, with respect to the specimens of Examples 1 and 2 using each passivating solution containing 0.1% by mass and 1% by mass of citric acid, another passivating solution is used. The average corrosion rate was smaller than that of the test specimen, and it had the best corrosion resistance. On the other hand, for the test pieces of Comparative Examples 2, 3 and 4 using the passivating solutions containing 5% by mass, 20% by mass and 40% by mass citric acid, the passivity without citric acid was obtained. The average corrosion rate was higher than that of the test piece of Comparative Example 1 using the chemical treatment solution, and the corrosion resistance was lowered.
クエン酸を含まない不動態化処理液を用いた比較例１の供試体の不動態皮膜と、クエン酸を１質量％含有する不動態化処理液を用いた実施例２の供試体の不動態皮膜と、について、オージェ電子分光分析を行った。分析条件については、イオンガン圧力を６．０×１０−２Ｐａ、加速電圧を１０ｋＶとした。 Passivation film of the test piece of the comparative example 1 using the passivating treatment solution containing no citric acid and passivation of the test piece of the example 2 using the passivating treatment solution containing 1% by mass of citric acid Auger electron spectroscopy analysis was performed on the film. Regarding the analysis conditions, the ion gun pressure was 6.0 × 10 −2 Pa, and the acceleration voltage was 10 kV.
図６は、比較例１の供試体における不動態皮膜のオージェ電子分光分析結果を示すグラフである。図７は、実施例２の供試体における不動態皮膜のオージェ電子分光分析結果を示すグラフである。図６及び図７のグラフでは、横軸に表面からのスパッタ時間（ｍｉｎ）を取り、縦軸に原子濃度を取り、Ｆｅ（鉄）、Ｃｒ（クロム）、Ｏ（酸素）、Ｃ（炭素）の原子濃度を実線等で表している。なお、図６のグラフのスパッタ時間が５ｍｉｎの位置と、図７のグラフのスパッタ時間が８ｍｉｎの位置とは、基材と不動態皮膜との界面の位置を示している。 FIG. 6 is a graph showing the results of Auger electron spectroscopy analysis of the passive film in the sample of Comparative Example 1. FIG. 7 is a graph showing the results of Auger electron spectroscopy analysis of the passive film in the sample of Example 2. In the graphs of FIGS. 6 and 7, the abscissa represents the sputtering time (min) from the surface, and the ordinate represents the atomic concentration, and Fe (iron), Cr (chromium), O (oxygen), C (carbon) The atomic concentration of is indicated by a solid line or the like. The position of the sputtering time of 5 min in the graph of FIG. 6 and the position of 8 min of the sputtering time of the graph of FIG. 7 indicate the position of the interface between the substrate and the passive film.
また、図８は、比較例１及び実施例２の供試体の不動態皮膜におけるＦｅ濃度に対するＣｒ濃度の比率の比較を示すグラフである。図８のグラフにおいて、横軸に表面からのスパッタ時間（ｍｉｎ）を取り、縦軸にＣｒ／Ｆｅ比率(Ｆｅ原子濃度に対するＣｒ原子濃度の比率)を取り、比較例１及び実施例２の供試体のデータを実線等で表している。なお、Ｃｒ／Ｆｅ比率については、図６及び図７に示すＦｅ原子濃度とＣｒ原子濃度とから算出した。 FIG. 8 is a graph showing a comparison of the ratio of the Cr concentration to the Fe concentration in the passive films of the test pieces of Comparative Example 1 and Example 2. In the graph of FIG. 8, the abscissa represents the sputtering time (min) from the surface, and the ordinate represents the Cr / Fe ratio (the ratio of the Cr atomic concentration to the Fe atomic concentration). The data of the sample is represented by a solid line or the like. The Cr / Fe ratio was calculated from the Fe atom concentration and the Cr atom concentration shown in FIG. 6 and FIG.
図８のグラフから明らかなように、実施例２の供試体の不動態皮膜は、比較例１の供試体の不動態皮膜よりも、表面（０ｍｉｎ）から約６ｍｉｎの範囲でＣｒ／Ｆｅ比率が大きくなり、不動態皮膜中にＣｒが濃化していることがわかった。 As apparent from the graph of FIG. 8, the passive film of the sample of Example 2 has a Cr / Fe ratio in the range of about 6 minutes from the surface (0 min) than the passive film of the sample of Comparative Example 1 It became large and it turned out that Cr is concentrated in a passive film.
以上の評価結果から、クエン酸を０．１質量％、１質量％含有する各不動態化処理液を用いた実施例１、２の供試体については、図４及び図５に示すように、耐海水腐食性、耐孔食性ともに耐食性が向上することがわかった。実施例１、２の供試体に用いた不動態化処理液のｐＨは、図３のグラフから３．１と２．５であり、ＳＵＳ６３０の脱不動化ＰＨである約２．４よりも高いので、安定した不動態皮膜が形成されたと考えられる。また、実施例１、２の供試体に用いた不動態化処理液には、クエン酸が含まれているので、不動態皮膜の形成時に、このクエン酸が不動態皮膜中に含まれる鉄分（鉄イオン）と錯体を形成することで、鉄分が溶解、除去されて、図８に示すように不動態皮膜中に含まれるクロム濃度が高くなり、耐食性が向上したと考えられる。 From the above evaluation results, as shown in FIGS. 4 and 5, the test pieces of Examples 1 and 2 using each passivating solution containing 0.1 mass% and 1 mass% of citric acid, It was found that corrosion resistance was improved in both seawater corrosion resistance and pitting corrosion resistance. The pH of the passivating solution used in the test pieces of Examples 1 and 2 is 3.1 and 2.5 according to the graph of FIG. 3, which is higher than about 2.4 which is the deimmobilized PH of SUS630. Therefore, it is considered that a stable passive film was formed. In addition, since the passivating solution used in the test pieces of Examples 1 and 2 contains citric acid, the iron component contained in the passivating film when this passivating film is formed By forming a complex with iron ion, iron is dissolved and removed, and as shown in FIG. 8, the concentration of chromium contained in the passive film becomes high, and the corrosion resistance is considered to be improved.
これに対して、比較例１の供試体では、不動態化処理液にクエン酸が含まれていないことから、不動態皮膜中に含まれるクロム濃度が低くなり、耐食性が低下したと考えられる。また、比較例２から４の供試体に用いた不動態化処理液のｐＨは、図３のグラフから２．１、１．６、１．１であり、ＳＵＳ６３０の脱不動化ｐＨである約２．４よりも低いので、安定した不動態皮膜が形成されなかったと考えられる。 On the other hand, in the test piece of Comparative Example 1, the citric acid is not contained in the passivating treatment liquid, so the concentration of chromium contained in the passivating film is lowered, and the corrosion resistance is considered to be lowered. Further, the pH of the passivating solution used in the test pieces of Comparative Examples 2 to 4 is 2.1, 1.6, and 1.1 from the graph of FIG. As it is lower than 2.4, it is considered that a stable passive film was not formed.
Ｓ１０ 前処理工程、
Ｓ１２ 不動態化処理工程。
S10 pretreatment process,
S12 passivation process step.
Claims (6)
前記ステンレス鋼部品に、１質量％の過酸化水素と、前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる含有率未満のクエン酸と、を含有し、残部が水からなる不動態化処理液を塗布または浸漬して不動態化処理する不動態化処理工程を備え、
前記不動態化処理液は、残部の水の一部に代えて、カルボキシメチルセルロース、カルボキシメチルセルロース化合物、キサンタンガムまたはペクチンを含有することを特徴とするステンレス鋼部品の不動態化処理方法。 A method of passivating stainless steel parts, comprising
The stainless steel part contains 1% by mass of hydrogen peroxide and citric acid which is less than the content of the stainless steel forming the stainless steel part to be depassivated pH, and the remainder is water A passivation treatment step of applying or immersing the treatment solution for passivation treatment;
The passivation treatment method of stainless steel parts characterized in that the passivation treatment liquid contains carboxymethylcellulose, a carboxymethylcellulose compound, xanthan gum or pectin in place of a part of the remaining water.
前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨが２．５未満であり、
前記不動態化処理液は、クエン酸の含有率が、０．１質量％以上であり、前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる含有率未満であることを特徴とするステンレス鋼部品の不動態化処理方法。 A method of passivation treatment of stainless steel parts according to claim 1,
The passivating pH of the stainless steel forming said stainless steel part is less than 2.5,
The passivation treatment liquid is characterized in that the content of citric acid is 0.1% by mass or more and is less than the content at which the depassivated pH of stainless steel forming the stainless steel part is obtained. Method of passivation treatment of stainless steel parts.
前記不動態化処理液は、クエン酸の含有率が、０．１質量％以上１質量％以下であることを特徴とするステンレス鋼部品の不動態化処理方法。 A method of passivation treatment of stainless steel parts according to claim 2, wherein
The passivation treatment method of stainless steel parts characterized in that a content of citric acid is 0.1% by mass or more and 1% by mass or less.
１質量％の過酸化水素と、ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる含有率未満のクエン酸と、を含有し、残部が水からなり、
残部の水の一部に代えて、カルボキシメチルセルロース、カルボキシメチルセルロース化合物、キサンタンガムまたはペクチンを含有することを特徴とするステンレス鋼部品用の不動態化処理液。 Passivation treatment solution for stainless steel parts,
Containing 1% by mass of hydrogen peroxide and citric acid less than the content that causes depassivating pH of stainless steel forming a stainless steel part, the balance being water
A passivating solution for stainless steel parts, which comprises carboxymethylcellulose, a carboxymethylcellulose compound, xanthan gum or pectin in place of a part of the remaining water.
前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨが２．５未満であり、
クエン酸の含有率が、０．１質量％以上であり、前記ステンレス鋼部品を形成するステンレス鋼の脱不動態化ｐＨとなる含有率未満であることを特徴とするステンレス鋼部品用の不動態化処理液。 A passivating solution for stainless steel parts according to claim 4 .
The passivating pH of the stainless steel forming said stainless steel part is less than 2.5,
A passivity for stainless steel parts characterized in that the content of citric acid is 0.1% by mass or more and is less than the content to be the depassivated pH of the stainless steel forming the stainless steel parts. Treatment solution.
クエン酸の含有率が、０．１質量％以上１質量％以下であることを特徴とするステンレス鋼部品用の不動態化処理液。
A passivating solution for stainless steel parts according to claim 5 ,
A passivating solution for stainless steel parts, wherein the content of citric acid is 0.1% by mass or more and 1% by mass or less.
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