JP5678505B2 - Method of forming anti-corrosion coating for offshore steel structures in tidal currents - Google Patents
Method of forming anti-corrosion coating for offshore steel structures in tidal currents Download PDFInfo
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- JP5678505B2 JP5678505B2 JP2010166912A JP2010166912A JP5678505B2 JP 5678505 B2 JP5678505 B2 JP 5678505B2 JP 2010166912 A JP2010166912 A JP 2010166912A JP 2010166912 A JP2010166912 A JP 2010166912A JP 5678505 B2 JP5678505 B2 JP 5678505B2
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- 239000011248 coating agent Substances 0.000 title claims description 63
- 238000000576 coating method Methods 0.000 title claims description 63
- 229910000831 Steel Inorganic materials 0.000 title claims description 46
- 239000010959 steel Substances 0.000 title claims description 46
- 238000000034 method Methods 0.000 title claims description 21
- 238000005260 corrosion Methods 0.000 title claims description 19
- 238000004070 electrodeposition Methods 0.000 claims description 80
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical group [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 26
- 230000015572 biosynthetic process Effects 0.000 claims description 16
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 13
- 238000010276 construction Methods 0.000 claims description 13
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 13
- 239000000347 magnesium hydroxide Substances 0.000 claims description 13
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims description 13
- 239000013535 sea water Substances 0.000 claims description 12
- 238000006467 substitution reaction Methods 0.000 claims description 6
- 230000006641 stabilisation Effects 0.000 claims description 5
- 238000011105 stabilization Methods 0.000 claims description 5
- 230000007797 corrosion Effects 0.000 claims 1
- 239000011253 protective coating Substances 0.000 claims 1
- 239000003643 water by type Substances 0.000 claims 1
- 239000011777 magnesium Substances 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 239000011575 calcium Substances 0.000 description 3
- 230000005611 electricity Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
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Description
本発明は、有潮流海域での海洋鋼構造物の防食被膜形成方法に関するものである。 The present invention relates to a method for forming an anticorrosion coating for a marine steel structure in a tidal current area.
一般に、岸壁等に護岸のために設けられる鋼矢板、橋梁や桟橋等に設けられる鋼管杭、或いはコンクリート構造物の表面を鉄鋼部材で被覆した鋼ケーソン等の海洋鋼構造物は、その一部が海水に水没した状態で設けられており、非常に錆が発生し易い環境に晒されている。 In general, some steel marine structures such as steel sheet piles provided on the quay for revetment, steel pipe piles provided on bridges and piers, etc., or steel caissons whose concrete structures are covered with steel members It is provided in a state where it is submerged in seawater, and is exposed to an environment where rust is likely to occur.
従って、このような海洋鋼構造物では、長期間の使用により錆が発生し減肉して強度が低下するため、補強工事或いは取替工事等を行う必要が生じるが、該補強工事或いは取替工事には多大の費用が掛かるため、水没部では防食電着被膜を形成して前記海洋鋼構造物の寿命延長を図ることが行われている。 Accordingly, in such marine steel structures, rust is generated due to long-term use and the thickness is reduced and the strength is reduced. Therefore, it is necessary to perform reinforcement work or replacement work. Since a great deal of cost is required for construction, it is attempted to extend the life of the marine steel structure by forming an anticorrosive electrodeposition coating in the submerged area.
海洋鋼構造物へ防食電着被膜を形成する際には、海洋鋼構造物の海水に水没した水没部に対して陽極を配置し、陽極と海洋鋼構造物との間に設けた直流電源により陽極と海洋鋼構造物に直流電流を通電する。これにより海水に溶存するカルシウムイオン（Ｃａ2+）やマグネシウムイオン（Ｍｇ2+）等の陽イオンが陰極としての海洋鋼構造物へ向かって海水中を泳動し、該海洋鋼構造物において電子を得ることとなり、該海洋鋼構造物の水没部表面に、炭酸カルシウム及び水酸化マグネシウム等を主成分とする防食電着被膜を形成する（例えば、特許文献１、２参照）。ここで特許文献１には、港湾環境では、０．５〜５［Ａ／ｍ2］の比較的高電流密度で通電期間を３〜７日とし、防食電着被膜を形成する点が記載されている。又、特許文献２には、約４０００［ＡＨ／ｍ2］の通電により、厚さ約５［ｍｍ］以上の防食電着被膜を素地表面に形成する点が記載されている。
When forming an anticorrosive electrodeposition coating on a marine steel structure, an anode is placed on the submerged part of the marine steel structure that has been submerged in seawater, and a direct current power source provided between the anode and the marine steel structure is used. Direct current is passed through the anode and marine steel structure. As a result, cations such as calcium ions (Ca 2+ ) and magnesium ions (Mg 2+ ) dissolved in seawater migrate in the seawater toward the marine steel structure as a cathode, and electrons are emitted from the marine steel structure. As a result, an anticorrosion electrodeposition film mainly composed of calcium carbonate, magnesium hydroxide, or the like is formed on the surface of the submerged portion of the marine steel structure (see, for example,
更に防食電着被膜で防食効果を発揮する組成は、所定の硬度を有する炭酸カルシウムであることから、防食電着被膜を形成した後、電流の供給を停止し、海水存在下で防食電着被膜の水酸化マグネシウムを置換反応により炭酸カルシウムに置き換えて安定化させることが考えられている（例えば、特許文献３参照）。 Furthermore, since the composition exhibiting the anticorrosive effect in the anticorrosion electrodeposition coating is calcium carbonate having a predetermined hardness, after forming the anticorrosion electrodeposition coating, the supply of current is stopped, and the anticorrosion electrodeposition coating in the presence of seawater. It is considered that the magnesium hydroxide is replaced with calcium carbonate by a substitution reaction for stabilization (for example, see Patent Document 3).
しかしながら、特許文献１、２に記載されている方法を、流れがある海域（有潮流海域）に適用した場合には、電気化学反応で形成されたアルカリ性雰囲気が潮流により拡散・希釈されるため、防食電着被膜を適切に形成することができないという問題があった。また拡散・希釈に対応して高い電流密度を用いる場合には、下記の反応式（１）により鋼材表面での水素ガスの発生量が増加するため、防食電着被膜が剥離する懸念があり、施工期間を把握することができないという問題があった。
２Ｈ2Ｏ＋２ｅ−→２ＯＨ−＋Ｈ2 …（１）
However, when the methods described in
2H 2 O + 2e − → 2OH − + H 2 (1)
また特許文献３に記載されている方法を適用する場合には、炭酸カルシウムの析出がｐＨ８〜９であり、水酸化マグネシウムの析出がｐＨ９〜１０であり、電流密度の増加とｐＨの上昇に伴って水酸化マグネシウムの析出する割合が増えるため、防食電着被膜の形成する電流密度の条件や、水酸化マグネシウムを炭酸カルシウムに置き換える期間を適切に設定できず、防食電着被膜を安定化して適切に形成することができないという問題があった。
Moreover, when applying the method described in
本発明は、斯かる実情に鑑み、流れがある海域において、施工期間を把握して防食電着被膜を適切に形成する有潮流海域での海洋鋼構造物の防食被膜形成方法を提供しようとするものである。 In view of such circumstances, the present invention seeks to provide a method for forming an anti-corrosion coating for a marine steel structure in a tidal current area in which the construction period is grasped and an anti-corrosion electrodeposition coating is appropriately formed in an area where there is a flow. Is.
本発明は、海洋鋼構造物の海水に水没した水没部に対し所要の間隔をあけて陽極を設け、該陽極と海洋鋼構造物との間に直流電源を設けて直流電流を通電することにより、海洋鋼構造物の水没部表面に防食電着被膜を形成する有潮流海域での海洋鋼構造物の防食被膜形成方法において、潮流速が０より大きく且つ最大潮流速以下となる有潮流海域で、防食電着被膜を形成する際の電流密度を３［Ａ／ｍ２］以上５［Ａ／ｍ２］以下にし、
前記防食電着被膜の形成時の電流密度［Ａ／ｍ ２ ］と、目標の膜厚［μｍ］を決め、
膜厚［μｍ］＝４．９×通電量［Ａ・ｄａｙ／ｍ ２ ］
の式から通電期間［ｄａｙ］を決定して施工することを特徴とする有潮流海域での海洋鋼構造物の防食被膜形成方法にかかるものである。
The present invention provides an anode with a predetermined interval with respect to a submerged portion of a marine steel structure submerged in seawater, and a direct current is applied by providing a direct current power source between the anode and the marine steel structure. In an anti-corrosion coating formation method for marine steel structures in a tidal current area where an anti-corrosion electrodeposition film is formed on the submerged surface of the marine steel structure, the tidal current is greater than 0 and less than or equal to the maximum tidal current. The current density when forming the anticorrosion electrodeposition film is 3 [A / m 2 ] or more and 5 [A / m 2 ] or less ,
Determine the current density [A / m 2 ] and the target film thickness [μm] when forming the anticorrosion electrodeposition coating ,
Film thickness [μm] = 4.9 × energization amount [A · day / m 2 ]
The present invention relates to a method for forming an anticorrosion coating for a marine steel structure in a tidal current area, wherein the construction is carried out by determining the energization period [day] from
上記手段によれば、以下のような作用が得られる。 According to the above means, the following operation can be obtained.
流れがある海域において、電流密度を３［Ａ／ｍ2］以上５［Ａ／ｍ2］以下にして施工すれば、防食電着被膜が実質的に付着しない状態や、防食電着被膜が剥離する状態を回避することが確認され、防食電着被膜を適切に形成することが可能となる。 If the current density is set to 3 [A / m 2 ] or more and 5 [A / m 2 ] or less in the sea area where there is a flow, the anticorrosion electrodeposition coating does not substantially adhere or the anticorrosion electrodeposition coating peels off. It is confirmed that the state to be prevented is avoided, and the anticorrosion electrodeposition coating can be appropriately formed.
前記有潮流海域での海洋鋼構造物の防食被膜形成方法においては、海洋鋼構造物の水没部表面に防食電着被膜を形成した後、電流の供給を停止し、海水存在下で防食電着被膜の水酸化マグネシウムを置換反応により炭酸カルシウムに置き換えて安定化させる期間を８日以上２０日以下にするので、施工期間を適確に把握し、防食電着被膜を適切に形成することが可能となる。 In the method of forming an anti-corrosion coating for marine steel structures in the tidal current area, after forming an anti-corrosion electrodeposition coating on the surface of the marine steel structure, the current supply is stopped, and the anti-corrosion electrodeposition is performed in the presence of seawater. The period of stabilization by replacing magnesium hydroxide in the film with calcium carbonate by a substitution reaction is set to 8 days or more and 20 days or less, so that the construction period can be accurately grasped and an anticorrosion electrodeposition film can be formed appropriately. It becomes.
本発明の有潮流海域での海洋鋼構造物の防食被膜形成方法によれば、潮流速が０より大きく且つ最大潮流速以下となる有潮流海域において防食電着被膜の形成するための電流密度を特定することにより、施工期間を把握し、防食電着被膜を適切に形成することができるという優れた効果を奏し得る。 According to the method for forming an anti-corrosion coating for marine steel structures in a tidal current area of the present invention, the current density for forming an anti-corrosion electrodeposition film in a tidal current area where the tide flow velocity is greater than 0 and less than or equal to the maximum tide flow velocity is obtained. By specifying, it is possible to obtain an excellent effect of grasping the construction period and appropriately forming the anticorrosion electrodeposition coating.
以下、本発明の実施の形態を添付図面を参照して説明する。 Embodiments of the present invention will be described below with reference to the accompanying drawings.
有潮流海域において防食電着被膜を形成する際には、図１に示す如く海洋鋼構造物１の海水に水没した水没部２に対し所要の間隔をあけて陽極３を設け、該陽極３と海洋鋼構造物１との間に直流電源４を設けて直流電流を通電することにより防食電着被膜５を形成する。また防食電着被膜５を形成する試験では、海洋鋼構造物１に見立てた試験片に防食電着被膜５を形成して試験を行った。試験では、防食電着被膜５の膜厚形成における電流密度［試験１］、防食電着被膜５の形成後の膜厚変化［試験２］、防食電着被膜５の水酸化マグネシウムから炭酸カルシウムへの組成変化［試験３］の評価を行った。ここで有潮流海域とは、潮流速が０より大きく且つ最大潮流速以下となる海域であって、潮流速が０より大きく１０ノット以下、好ましくは０より大きく５ノット以下の海域を意味している。
When forming an anticorrosion electrodeposition coating in a tidal current area, an
前記防食電着被膜５の形成条件は、以下に示す通りである。
・試験片（陰極）：ＳＳ４００、４００×４５０×６［ｍｍ］
（有効面積：１０５０［ｃｍ2］）
・陽極：ＳＳ４００、４００×４５０×６［ｍｍ］
・試験片の水深：（最低水位Ｌ．Ｗ．Ｌ．）−１．０［ｍ］
・電極間距離：５００［ｍｍ］
・被膜形成時の陰極電流密度：２〜１０［Ａ／ｍ2］
The formation conditions of the
Test piece (cathode): SS400, 400 × 450 × 6 [mm]
(Effective area: 1050 [cm 2 ])
・ Anode: SS400, 400 × 450 × 6 [mm]
-Water depth of test piece: (minimum water level LW L) -1.0 [m]
・ Distance between electrodes: 500 [mm]
Cathode current density during film formation: 2 to 10 [A / m 2 ]
［試験１］
上記条件で防食電着被膜の膜厚における電流密度を評価する際には、潮流速が０より大きく５ノット以下の海域で試験を行い、防食電着被膜形成時の電流密度を２［Ａ／ｍ２］から１０［Ａ／ｍ２］までの範囲にして設定し、単位通電量あたりの電流密度［１Ａ・ｄａｙ／ｍ２］で形成される防食電着被膜の膜厚［μｍ］を複数計測した。
[Test 1]
When evaluating the current density at the film thickness of the anticorrosive electrodeposition film under the above conditions, a test was conducted in a sea area where the tidal flow velocity was greater than 0 and less than or equal to 5 knots, and the current density when forming the anticorrosion electrodeposition film was 2 [A / m 2 ] to 10 [A / m 2 ], and a plurality of film thicknesses [μm] of the anticorrosion electrodeposition film formed at a current density [1 A · day / m 2 ] per unit energization amount. Measured.
この結果、図２に示すごとく電流密度を３［Ａ／ｍ２］以上５［Ａ／ｍ２］以下にした範囲では、ほぼ同じ効率で防食電着被膜が形成されることが確認された。一方、電流密度が７［Ａ／ｍ２］以上では被膜の剥離が確認され、電流密度が２［Ａ／ｍ２］では通電時間４日経過時においても被膜が適切に形成されず、効率が悪いことが確認された。従って潮流速が０より大きく５ノット以下の海域で効率よく被膜を形成させるためには、電流密度を３［Ａ／ｍ２］以上５［Ａ／ｍ２］以下の範囲にして通電すれば良いことが明らかとなった。 As a result, as shown in FIG. 2, it was confirmed that the anticorrosion electrodeposition film was formed with substantially the same efficiency in a range where the current density was 3 [A / m 2 ] or more and 5 [A / m 2 ] or less. On the other hand, when the current density is 7 [A / m 2 ] or more, peeling of the film is confirmed, and when the current density is 2 [A / m 2 ], the film is not properly formed even when the energization time is 4 days, and the efficiency is improved. It was confirmed that it was bad. Therefore, in order to efficiently form a film in a sea area where the tide velocity is greater than 0 and less than or equal to 5 knots, the current density may be set within a range of 3 [A / m 2 ] to 5 [A / m 2 ]. It became clear.
また電流密度を３［Ａ／ｍ２］以上５［Ａ／ｍ２］以下の範囲にして通電した場合、通電量と、防食電着被膜の膜厚の関係を調べた。その結果、図３に示すごとく、ほぼ通電量に比例して被膜が形成されていることが確認でき、通電量と防食電着被膜の膜厚との関係について次の式を見出すことができた。
膜厚［μｍ］＝４．９×通電量［Ａ・ｄａｙ／ｍ2］
よって目標の膜厚［μｍ］と電流密度［Ａ／ｍ２］を決めれば、施工のための通電期間［ｄａｙ］の算出が可能である。なお、図３中ではｙ＝４．９Ｘで記載している。
Further, when the current density was applied in the range of 3 [A / m 2 ] to 5 [A / m 2 ], the relationship between the amount of current and the film thickness of the anticorrosive electrodeposition coating was examined. As a result, as shown in FIG. 3, it was confirmed that a film was formed almost in proportion to the energization amount, and the following equation was found for the relationship between the energization amount and the film thickness of the anticorrosion electrodeposition coating. .
Film thickness [μm] = 4.9 × energization amount [A · day / m 2 ]
Therefore, if the target film thickness [μm] and current density [A / m 2 ] are determined, the energization period [day] for construction can be calculated. In FIG. 3, y = 4.9X.
［試験２］
防食電着被膜の形成後の膜厚変化を評価する際には、同様に潮流速が０より大きく５ノット以下の海域で試験を行い、電流密度を３［Ａ／ｍ２］から７［Ａ／ｍ２］までの範囲にして防食電着被膜を形成し、通電停止後の防食電着被膜の膜厚減少速度［μｍ／日］を複数計測した。ここで通電停止後の期間は、通電停止初期の期間（２日〜８日）とした。なお電流密度が２［Ａ／ｍ２］の場合には、防食電着被膜を適切に形成できないため、防食電着被膜の膜厚減少速度を計測しなかった。
[Test 2]
When evaluating the film thickness change after the formation of the anticorrosive electrodeposition film, similarly, the test was conducted in a sea area where the tidal flow velocity was greater than 0 and less than 5 knots, and the current density was changed from 3 [A / m 2 ] to 7 [A / M 2 ], an anticorrosion electrodeposition film was formed, and a plurality of film thickness reduction rates [μm / day] of the anticorrosion electrodeposition film after stopping energization were measured. Here, the period after the energization stop was set to the initial period (2 to 8 days). In addition, when the current density was 2 [A / m 2 ], since the anticorrosion electrodeposition film could not be formed properly, the thickness reduction rate of the anticorrosion electrodeposition film was not measured.
この結果、図４に示すごとく電流密度を３［Ａ／ｍ２］または４［Ａ／ｍ２］にして防食電着被膜を形成した場合には、膜厚の減少が少ないことが確認された。一方、電流密度５［Ａ／ｍ２］以上で防食電着被膜を形成した場合には、通電停止初期に約２０μｍ／日の速度で被膜厚が減少することが確認された。 As a result, it was confirmed that when the anticorrosion electrodeposition film was formed with a current density of 3 [A / m 2 ] or 4 [A / m 2 ] as shown in FIG. . On the other hand, when the anticorrosion electrodeposition film was formed at a current density of 5 [A / m 2 ] or more, it was confirmed that the film thickness decreased at a rate of about 20 μm / day at the beginning of energization stop.
従って、流れがある海域において膜厚の減少が少なく、効率良く防食電着被膜を形成するためには、通電時の電流密度を３［Ａ／ｍ２］以上４［Ａ／ｍ２］以下にすることが好ましいことが明らかとなった。 Therefore, in order to form an anticorrosion electrodeposition film efficiently in a sea area where there is a flow, the current density during energization is 3 [A / m 2 ] or more and 4 [A / m 2 ] or less. It has become clear that this is preferable.
ここで電流密度を５［Ａ／ｍ２］にして防食電着被膜を形成し、通電停止後の防食電着被膜の膜厚変化を計測した場合には、図５に示すごとく通電停止後５日以降において、膜厚はほぼ変化しておらず、被膜が安定に存在していることが確認された。 Here, when the current density is 5 [A / m 2 ] to form the anticorrosion electrodeposition film and the change in the thickness of the anticorrosion electrodeposition film after the energization is stopped, as shown in FIG. After the day, the film thickness was not substantially changed, and it was confirmed that the film existed stably.
従って電流密度を５［Ａ／ｍ２］以上にして防食電着被膜を形成する場合は、通電停止後５日間で１００μｍ程度（５日×２０μｍ／日）膜厚が減少することを予め見込み、膜厚［μｍ］＝４．９×通電量［Ａ・ｄａｙ／ｍ2］の式より、電気密度を５［Ａ／ｍ２］にして４日間［ｄａｙ］通電し、通電量約２０［Ａ・ｄａｙ／ｍ2］を余分に付加すれば、膜厚の減少分１００μｍの影響を回避できると推定される。 Therefore, when forming an anticorrosion electrodeposition film with a current density of 5 [A / m 2 ] or more, it is anticipated that the film thickness will decrease by about 100 μm (5 days × 20 μm / day) in 5 days after the energization is stopped, From the formula of film thickness [μm] = 4.9 × energization amount [A · day / m 2 ], the electricity density is 5 [A / m 2 ] and the electricity is energized for 4 days [day]. If day / m 2 ] is added, it is estimated that the influence of the decrease in film thickness of 100 μm can be avoided.
［試験３］
防食電着被膜の水酸化マグネシウムから炭酸カルシウムへの組成変化を評価する際には、同様に潮流速が０より大きく５ノット以下の海域で試験を行い、電流密度を３［Ａ／ｍ２］から１０［Ａ／ｍ２］までの範囲にして防食電着被膜を海水中に形成し、電流の供給を停止した後の日数を浸漬日数として記録すると同時に防食電着被膜の組成比（ＣａＣＯ3／Ｍｇ（ＯＨ）2）を計測した。ここで水酸化マグネシウム（Ｍｇ（ＯＨ）2）を炭酸カルシウム（ＣａＣＯ3）に置き換える置換反応は、下記の反応式（２）〜（４）により成り立っていると考えられている。
Ｍｇ（ＯＨ）2 → Ｍｇ2+＋２ＯＨ− …（２）
Ｃａ2+＋Ｈ2ＣＯ3＋２ＯＨ− → ＣａＣＯ3＋２Ｈ2Ｏ …（３）
Ｍｇ（ＯＨ）2＋Ｃａ2+＋Ｈ2ＣＯ3 → Ｍｇ2+＋ＣａＣＯ3＋２Ｈ2Ｏ …（４）
[Test 3]
When evaluating the composition change from magnesium hydroxide to calcium carbonate in the anticorrosion electrodeposition coating, the test was similarly conducted in a sea area where the tidal velocity was greater than 0 and less than 5 knots, and the current density was 3 [A / m 2 ]. To 10 [A / m 2 ], the anticorrosion electrodeposition coating is formed in seawater, and the number of days after the supply of current is stopped is recorded as the number of days of immersion. At the same time, the composition ratio of the anticorrosion electrodeposition coating (CaCO 3 / Mg (OH) 2 ). Here, the substitution reaction for replacing magnesium hydroxide (Mg (OH) 2 ) with calcium carbonate (CaCO 3 ) is considered to be constituted by the following reaction formulas (2) to (4).
Mg (OH) 2 → Mg 2+ + 2OH − (2)
Ca 2+ + H 2 CO 3 + 2OH − → CaCO 3 + 2H 2 O (3)
Mg (OH) 2 + Ca 2+ + H 2 CO 3 → Mg 2+ + CaCO 3 + 2H 2 O (4)
この結果、電流密度を３［Ａ／ｍ２］から１０［Ａ／ｍ２］までの範囲にして防食電着被膜を形成した場合、いずれも水酸化マグネシウムの割合が高い防食電着被膜であって、図６に示すごとく３［Ａ／ｍ２］から７［Ａ／ｍ２］までの防食電着被膜は、浸漬８日以上、好ましくは１０日以上２０日以下で防食電着被膜の水酸化マグネシウムを炭酸カルシウムに置き換え、組成比が１〜２程度になっている。ここで電流密度１０［Ａ／ｍ２］の防食電着被膜は［実験１］で示すように剥離を生じることから適切な膜厚を形成することできなかった。 As a result, when the anticorrosion electrodeposition film was formed with a current density in the range of 3 [A / m 2 ] to 10 [A / m 2 ], all of the anticorrosion electrodeposition films had a high proportion of magnesium hydroxide. As shown in FIG. 6, the anticorrosion electrodeposition coating from 3 [A / m 2 ] to 7 [A / m 2 ] is immersed in water for 8 days or more, preferably 10 days or more and 20 days or less. Magnesium oxide is replaced with calcium carbonate, and the composition ratio is about 1-2. Here, the anticorrosion electrodeposition film having a current density of 10 [A / m 2 ] could not be formed with an appropriate thickness because peeling occurred as shown in [Experiment 1].
従って、流れがある海域（有潮流海域）において置換反応により防食電着被膜の水酸化マグネシウムを炭酸カルシウムに置き換えることが確認でき、好ましくは１０日以降で組成比が１〜２となって安定化することが明らかである。よって防食電着被膜を安定化するまでは、通電停止後１０日間が必要であり、安定化するための施工期間を推定することが可能である。 Therefore, it can be confirmed that magnesium hydroxide in the anti-corrosion electrodeposition film is replaced with calcium carbonate by substitution reaction in the sea area where there is a flow (tidal current area), and the composition ratio is preferably stabilized to 1-2 after 10 days. It is clear to do. Therefore, it takes 10 days after the energization is stopped until the anticorrosion electrodeposition coating is stabilized, and it is possible to estimate the construction period for stabilization.
而して、実施の形態例によれば、流れがある海域において、電流密度を３［Ａ／ｍ2］以上５［Ａ／ｍ2］以下にし、防食電着被膜が実質的に付着しない状態や、防食電着被膜が剥離する状態を回避し、施工期間を把握して防食電着被膜を適切に形成することができる。 Thus, according to the embodiment, the current density is 3 [A / m 2 ] or more and 5 [A / m 2 ] or less in the sea area where there is a flow, and the anticorrosion electrodeposition coating is not substantially attached. In addition, it is possible to avoid the state where the anticorrosion electrodeposition coating is peeled off, and to properly form the anticorrosion electrodeposition coating by grasping the construction period.
ここで電流密度を３［Ａ／ｍ2］より小さくした場合には、防食電着被膜が実質的に付着せず、電流密度を５［Ａ／ｍ2］より大きくした場合には、防食電着被膜が剥離する可能性があることから、電流密度を３［Ａ／ｍ2］以上５［Ａ／ｍ2］以下にして防食電着被膜を形成する必要がある。 Here, when the current density is less than 3 [A / m 2 ], the anticorrosion electrodeposition coating does not substantially adhere, and when the current density is greater than 5 [A / m 2 ], the anticorrosion electricity Since the deposited film may be peeled off, it is necessary to form the anticorrosive electrodeposited film by setting the current density to 3 [A / m 2 ] or more and 5 [A / m 2 ] or less.
有潮流海域での海洋鋼構造物の防食被膜形成方法においては、前記防食電着被膜の形成時の電流密度［Ａ／ｍ2］と、目標の膜厚［μｍ］を決め、
膜厚［μｍ］＝４．９×通電量［Ａ・ｄａｙ／ｍ2］
の式から通電期間［ｄａｙ］を決定して施工するので、防食電着被膜を形成する施工期間を適確に把握することができる。
In the anticorrosive coating forming method for marine steel structures in tidal current areas, the current density [A / m 2 ] and the target film thickness [μm] when forming the anticorrosive electrodeposition coating are determined,
Film thickness [μm] = 4.9 × energization amount [A · day / m 2 ]
Since the energization period [day] is determined from the formula of the construction, the construction period for forming the anticorrosion electrodeposition coating can be accurately grasped.
有潮流海域での海洋鋼構造物の防食被膜形成方法においては、海洋鋼構造物の水没部表面に防食電着被膜を形成した後、電流の供給を停止し、海水存在下で防食電着被膜の水酸化マグネシウムを置換反応により炭酸カルシウムに置き換えて安定化させる期間を８日以上２０日以下にするので、施工期間を適確に把握して防食電着被膜を適切に形成することができる。 In the method of forming an anti-corrosion coating for marine steel structures in tidal current areas, after forming an anti-corrosion electrodeposition coating on the surface of the submerged part of the marine steel structure, the current supply is stopped and the anti-corrosion electrodeposition coating in the presence of seawater. Since the magnesium hydroxide is replaced with calcium carbonate by a substitution reaction for a stabilization period of 8 days or more and 20 days or less, the construction period can be accurately grasped and an anticorrosion electrodeposition coating can be formed appropriately.
尚、本発明の有潮流海域での海洋鋼構造物の防食被膜形成方法は、上述の実施例にのみ限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。 In addition, the anticorrosive coating film forming method for marine steel structures in the tidal current area of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. Of course.
１ 海洋鋼構造物
２ 水没部
３ 陽極
４ 直流電源
５ 防食電着被膜
1
Claims (2)
前記防食電着被膜の形成時の電流密度［Ａ／ｍ ２ ］と、目標の膜厚［μｍ］を決め、
膜厚［μｍ］＝４．９×通電量［Ａ・ｄａｙ／ｍ ２ ］
の式から通電期間［ｄａｙ］を決定して施工することを特徴とする有潮流海域での海洋鋼構造物の防食被膜形成方法。 A marine steel structure is provided by providing a positive electrode with a predetermined interval with respect to the submerged portion of the marine steel structure submerged in seawater, and providing a DC power supply between the anode and the marine steel structure. In a method for forming an anti-corrosion coating for marine steel structures in a tidal current area where an anti-corrosion electrodeposition film is formed on the surface of the submerged part of the object, the anti-corrosion electrodeposition is performed in a tidal current area where the tide velocity is greater than 0 and less than or equal to the maximum tide velocity. The current density at the time of forming the film is 3 [A / m 2 ] or more and 5 [A / m 2 ] or less ,
Determine the current density [A / m 2 ] and the target film thickness [μm] when forming the anticorrosion electrodeposition coating ,
Film thickness [μm] = 4.9 × energization amount [A · day / m 2 ]
A method for forming an anti-corrosion coating for a marine steel structure in a tidal current area, wherein the construction is carried out by determining an energization period [day] from
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