JP3925296B2 - Anticorrosion method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は防食方法に係り、特に毒性や閉鎖性水域における富栄養化等の環境汚染問題を発生させることなく、水と接触する金属、特に鋼材の腐食を効果的に防止ないし抑制する方法に関するものである。
【０００２】
【従来の技術】
開放循環式冷却水系等の水系では、熱交換器、配管等の基材に、主として炭素鋼等の鋼材が使用されている。冷却水中に浸漬されている鋼材は、水中の溶存酸素や塩素イオン、硫酸イオン等により腐食され、孔食を発生させる。しかして、このような孔食は、銅、銅合金やステンレス鋼等の耐食材料においても起こる。
【０００３】
そこで、従来より、このような水系と接する金属材の腐食を抑制するために防食剤が用いられている。冷却水系で使用される防食剤は、それ自体は水に可溶性であるが、金属の表面に酸化皮膜、又は水に不溶性ないし難溶性の皮膜を形成して、金属イオンの溶出或いは溶存酸素の還元反応を妨げることによって腐食反応を抑制する。
【０００４】
防食剤としては、一般にクロム酸塩や亜鉛塩等の重金属塩や（ポリ）リン酸塩、有機リン化合物等が用いられている。
【０００５】
更に、クエン酸、酒石酸等のオキシカルボン酸が提案されている。
【０００６】
【発明が解決しようとする課題】
これらの従来使用されている防食剤のうち、クロム酸塩は優れた防食効果を奏する反面、低濃度で使用すると局部腐食が発生しやすい欠点がある。また、クロム酸塩は毒性が強く、その排出が厳しく規制されており、排水処理、回収処理が不可欠である。亜鉛塩は防食効果の面で若干問題があり、かつ排水として流れると規制上問題がある。
【０００７】
更に、リン酸塩は赤潮発生の原因となることなどから、最近では、閉鎖性水域における富栄養化防止の観点から、リンの排出が規制されている。
【０００８】
このため、現在、毒性や富栄養化等の環境汚染問題を発生させることなく、水系と接する鋼材等の金属の腐食を抑制することができる方法の出現が強く要望されている。
【０００９】
一方、オキシカルボン酸も規制物質を含まないものであるが、これは微生物により容易に分解され、防食効果を持続できないという欠点を有している。
【００１０】
本発明は、上記従来の問題点を解決し、環境汚染問題をひき起こすことなく、水系と接する金属の腐食を効果的に防止ないし抑制する防食方法を提供することを目的とする。
【００１１】
【課題を解決するための手段】
本発明の防食方法は、カルシウムイオンが存在する水系に、タングステン酸及び／又はその塩と水溶性ケイ酸塩とを、各々、Ｗ換算：ＳｉＯ２換算の重量割合で１１：１〜１：２となるように存在させ、かつ、カルボン酸系の低分子量ポリマーを該水系に添加する防食方法であって、前記カルボン酸系の低分子量ポリマーが、分子量５００〜１０００００の、ポリアクリル酸と３−アリロキシ−２−ヒドロキシプロパンスルホン酸との共重合体であることを特徴とする。
【００１２】
従来、水系の金属腐食抑制剤として、タングステン酸塩又は水溶性ケイ酸塩を用いることは知られている。しかしながら、タングステン酸塩は、良好な防食効果を有するが、比較的高価であることから、その実用化にも限度がある。これに対し、水溶性ケイ酸塩は、比較的安価であるが、防食効果が弱く、実用濃度においては、十分な防食効果は得られず、良好な防食剤とはいえなかった。
【００１３】
本発明者らは、このようなタングステン酸塩と水溶性ケイ酸塩の特性について鋭意検討を重ねた結果、タングステン酸又はその塩と水溶性ケイ酸塩との特定量の存在下で、特異的な相乗効果が奏され、優れた防食効果を得ることができることを見出し、本発明を完成させた。
【００１４】
【発明の実施の形態】
以下に本発明の防食方法の実施の形態を詳細に説明する。
【００１５】
本発明の方法は、開放冷却水系や密閉冷却水系、ブライン水系等の処理対象水系に、防食剤としてタングステン酸及び／又はタングステン酸塩と水溶性ケイ酸塩を添加するものである。
【００１６】
タングステン酸塩としては、タングステン酸の、ナトリウム塩、カリウム塩、アンモニウム塩等の公知の水溶性塩が挙げられる。
【００１７】
また、水溶性ケイ酸塩としては、ケイ酸のアルカリ金属塩が挙げられ、アルカリ金属としては、経済性、毒性の点から、ナトリウム、カリウムが好ましい。ケイ酸ナトリウムを用いる場合、そのＮａ２Ｏ／ＳｉＯ２（重量比）は、４／１〜１／４が好ましく、特に１／１〜１／４が好ましい。
【００１８】
タングステン酸及び／又はその塩についても、水溶性ケイ酸塩についても、各々１種を単独で用いても良く、２種以上を併用しても良い。
【００１９】
これらのタングステン酸及び／又はタングステン酸塩と水溶性ケイ酸塩との割合は、タングステン酸及び／又はタングステン酸塩中のＷと水溶性ケイ酸塩中のＳｉＯ２との重量比でＷ：ＳｉＯ２＝１１：１〜１：２、好ましくはＷ：ＳｉＯ２＝３：１〜１：１．４とする。このような配合割合とした場合に、極めて良好な相乗効果により、著しく高い防食効果が得られる。
【００２０】
本発明においては、処理対象水系にタングステン酸及び／又はタングステン酸塩と水溶性ケイ酸塩とを、上記配合割合となるように存在させるものであって、その添加形態は特に制限されず、これらの有効成分を予め所定割合に混合したものを水系に添加しても、また、各々別個に添加して、水系中で混合するようにしても良い。なお、水溶性ケイ酸塩が水系に予め所定量存在するときには、タングステン酸又はその塩のみを添加すれば良い。
【００２１】
これらの有効成分の使用濃度は、処理対象水系の性状やその腐食環境の程度に応じて決定されるが、一般には、水系内のタングステン酸及び／又はタングステン酸塩と水溶性ケイ酸塩との合計濃度が５００〜５０００ｍｇ／Ｌ、特に１００〜２０００ｍｇ／Ｌとなるように添加するのが好ましい。
【００２２】
本発明において、処理する水系のｐＨは７．５〜１０．０であることが好ましい。即ち、水系のｐＨが７．５未満であっても、１０．０を超えても腐食防止効果が低下し、いずれの場合も良好な防食効果を得ることができない。このため、水系のｐＨが７．５〜１０．０の範囲を外れる場合には、本発明の方法により処理するに先立ち、必要に応じて、ＮａＯＨ、ＫＯＨ等のアルカリや、ＨＣｌ、Ｈ２ＳＯ４等の酸を添加して、水系のｐＨを上記範囲に調整することが好ましい。
【００２３】
また、処理する水系にカルシウムイオンが存在すると、タングステン酸カルシウムの沈殿を生成するため、好ましくない。従って、タングステン酸カルシウムの沈殿生成を防止するために、カルボン酸系の低分子量ポリマーを水系に共存させる。このような低分子量ポリマーとしては、分子量５００〜１０００００の、ポリアクリル酸と３−アリロキシ−２−ヒドロキシプロパンスルホン酸（ＨＡＰＳ）との共重合体を用い、その添加量は水系のカルシウム硬度によっても異なるが、通常の場合、カルシウム硬度（ＣａＣＯ３換算：ｍｇ／Ｌ）に対して、１／１０００〜２倍の添加量（ｍｇ／Ｌ）とするのが好ましい。
【００２４】
なお、本発明においては、上記有効成分により十分な防食効果が得られるが、必要に応じて、他の防食剤、例えば、メルカプトベンゾチアゾール等のチアゾール類；ベンゾトリアゾール等のアゾール類；ヒドラジン類；シクロヘキシルアミン、アルキルアミン、アルカノールアミン、ポリアミン等の水溶性アミン類；エチレンイミン、ピロリジン、ピペリジン、ピペラジン、ケチミン等のイミン類；ホルムヒドロキサム酸、アセトヒドロキサム酸、ペンズヒドロキサム酸等のヒドロキサム酸類；カテコール類；タンニン類；リグニン類；ホスホン酸類；オキシカルボン酸類等の有機化合物や亜硝酸塩、各種リン酸塩、ホウ酸塩、亜鉛塩、ニッケル塩、アルミニウム塩、アルミン酸塩、モリブデン酸塩、バナジウム塩等の無機塩類等、その他、スケール防止剤、スライム除去剤等を併用しても良い。
【００２５】
【実施例】
以下に本発明を実験例を挙げて更に具体的に説明する。
【００２６】
実験例１〜４、比較実験例１〜６
純水に、塩化カルシウム溶液で３０ｍｇ／Ｌ（ａｓ ＣａＣＯ３）、炭酸水素ナトリウム溶液で５０ｍｇ／Ｌ（ａｓ ＣａＣＯ３）、硫酸マグネシウム溶液で３０ｍｇ／Ｌ（ａｓＣａＣＯ３）、塩化ナトリウム溶液で５０ｍｇ／Ｌ（ａｓＣｌ−）及び硫酸ナトリウム溶液で５０ｍｇ／Ｌ（ａｓ ＳＯ４ ２−）を添加して試験液とした。この試験液のｐＨは７であった。
【００２７】
得られた試験液を１Ｌビーカーに１Ｌ採り、表１に示す各種薬剤を添加して（比較例１においては無添加）、この液中に軟鋼試験片を各々１枚浸漬し、５０℃で５日間１６０ｒ．ｐ．ｍ．で回転腐食試験を行い、その腐食速度を調べ、結果を表１に示した。
【００２８】
【表１】
表１より、本発明に従って、タングステン酸塩と水溶性ケイ酸塩とを併用することにより、各薬剤を単独で添加した場合の添加濃度よりも低い添加濃度で、極めて優れた防食作用の相乗効果が得られることが明らかである。
【００３０】
実験例５〜１２、比較実験例７〜１０
純水に１級エチレングリコールを３０体積％の割合で溶解したものを使用し、塩化カルシウム溶液で３０ｍｇ／Ｌ（ａｓ ＣａＣＯ３）、炭酸水素ナトリウム溶液で８２ｍｇ／Ｌ（ａｓ
ＣａＣＯ３）、塩化ナトリウム溶液で５００ｍｇ／Ｌ（ａｓ
Ｃｌ−）、硫酸ナトリウム溶液で５００ｍｇ／Ｌ（ａｓ ＳＯ４ ２−）を添加して試験液とした。
【００３１】
この試験液に、薬剤無添加で、３０℃で３日間軟鋼試験片（ＳＰＣＣ ３１ｃｍ２）を浸漬して予め既発錆面を作成し、次いで表２に示す各種薬剤を添加し（比較実験例７は無添加）、ｐＨを７に調整した後、１０℃で７日間１８０ｒ．ｐ．ｍ．で回転腐食試験を行い、腐食減量を調べ、結果を表２に示した。なお、薬剤無添加の状態で３日間既発錆面の形成を行った際の腐食減量は９３ｍｇであった。
【００３２】
【表２】
表２より、タングステン酸塩と水溶性ケイ酸塩との併用により、既発錆面に対しても、各薬剤の単独添加では得られなかった優れた防食効果が得られることが明らかである。
【００３４】
実験例１３
タングステン酸ナトリウム２水和物と、低分子量ポリマー（アクリル酸と３−アリロキシ−２−ヒドロキシプロパンスルホン酸との共重合体，分子量５０００）と、ケイ酸ナトリウム（ケイ酸ソーダ３号）とＮａＯＨを脱イオン水に添加し、タングステン酸ナトリウム１５重量部、低分子量ポリマー１重量部、ケイ酸ナトリウム３３重量部、ＮａＯＨ３重量部、水４８重量部、ｐＨ１３の防食剤組成物（タングステン酸ナトリウムとケイ酸ナトリウムとのＷ換算：ＳｉＯ２換算重量比は８：１０）を調製し、この防食剤組成物について室温及び６０℃のインキュベーター中に静置し、３ヶ月後に沈澱物、析出物、外観変化の有無について観察し、結果を表３に示した。
【００３５】
【表３】
表３より、タングステン酸塩、水溶性ケイ酸塩及び低分子量ポリマーを含む防食剤組成物は一剤として配合した場合にも、製品の安定性に優れることがわかる。
【００３７】
実験例１４
脱イオン水に、炭酸カルシウムと、ｐＨ調整剤としてのＮａＯＨと、タングステン酸ナトリウム２水和物、低分子量ポリマー（アクリル酸と３−アリロキシ−２−ヒドロキシプロパンスルホン酸との共重合体，分子量５０００）とケイ酸ナトリウム（ケイ酸ソーダ３号）とを以下の濃度及び水質となるように添加して試験液を調製し、５０℃で４０時間静置した後、試験液のｐＨ、カルシウム硬度、タングステン酸ナトリウム濃度及び外観を調べ結果を表４に示した。
【００３８】
［試験液］
カルシウム硬度：５０ｍｇ／Ｌ（ａｓ ＣａＣＯ３）
Ｍアルカリ度：１００ｍｇ／Ｌ（ａｓ ＣａＣＯ３）
ｐＨ：８．０
タングステン酸ナトリウム：１５０ｍｇ／Ｌ（ａｓ Ｗ）
低分子量ポリマー：０，１０，２０，３０又は６０ｍｇ／Ｌ
ケイ酸ナトリウム：１００ｍｇ／Ｌ（ａｓ ＳｉＯ２）
【００３９】
【表４】
表４より、カルシウムイオンの存在でタングステン酸カルシウムが析出し、タングステン酸塩が消費されるが、低分子量ポリマーの添加で、タングステン酸カルシウムの析出を防止することができることがわかる。
【００４１】
実験例１５
純水に、塩化カルシウム溶液を５０ｍｇ／Ｌ（ａｓＣａＣＯ３）、炭酸水素ナトリウム溶液を５０ｍｇ／Ｌ（ａｓＣａＣＯ３）、塩化ナトリウム溶液を５０ｍｇ／Ｌ（ａｓＣｌ−）及び硫酸ナトリウム溶液を５０ｍｇ／Ｌ（ａｓＳＯ４ −）添加して試験液とした。更にＮａＯＨを３０００ｍｇ／Ｌとなるように添加した。そこへ、炭酸ガスをｐＨスタットで制御して吹き込み、試験期間中、ｐＨを７．０、７．５、８．０、８．５、９．０、９．５、１０．０、１０．５に保った。
【００４２】
各試験液にタングステン酸ナトリウム５０ｍｇ／Ｌ（ａｓ Ｗ）とケイ酸ナトリウム（ケイ酸ソーダ３号）２５ｍｇ／Ｌ（ａｓ ＳｉＯ２）とを添加し、各試験液中に軟鋼試験片を１枚浸漬し、５０℃で５日間１６０ｒ．ｐ．ｍ．で回転腐食試験を行い、その腐食速度を調べ、結果を表５に示した。
【００４３】
【表５】
表５より、水系のｐＨが７．５未満であったり、１０．０を超えると、十分な防食効果が得られず、本発明では、水系のｐＨを７．５〜１０．０の範囲とすることが好ましいことがわかる。
【００４５】
【発明の効果】
以上詳述した通り、本発明の防食方法は、水系に、特定割合のタングステン酸及び／又はタングステン酸塩と水溶性ケイ酸塩とを存在させるものとであって、２つの有効成分による優れた相乗効果により、著しく高い防食効果が得られ、水と接触する鋼材等の金属に対して優れた防食抑制ないし防止効果を奏する。
【００４６】
本発明によれば、少ない薬剤使用量で十分な効果が得られることから、防食処理コストの低減が図れ、しかも既発錆面に対しても優れた防食効果を奏する。更に排水中に、重金属塩が含まれないので毒性の問題がなく、またリンを含まず低ＣＯＤであるので富栄養化の問題もない。
【００４７】
このため、本発明によれば環境汚染問題を生起させることなく、金属の腐食を有効に防止し得る。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anticorrosion method, and more particularly to a method for effectively preventing or suppressing corrosion of metals, particularly steel materials, that come into contact with water without causing environmental pollution problems such as toxicity and eutrophication in closed water areas. It is.
[0002]
[Prior art]
In water systems such as an open circulation cooling water system, steel materials such as carbon steel are mainly used for base materials such as heat exchangers and pipes. The steel material immersed in the cooling water is corroded by dissolved oxygen, chlorine ions, sulfate ions, etc. in the water and generates pitting corrosion. Thus, such pitting corrosion also occurs in corrosion resistant materials such as copper, copper alloys and stainless steel.
[0003]
Therefore, conventionally, an anticorrosive agent has been used to suppress the corrosion of the metal material in contact with such an aqueous system. The anticorrosive used in the cooling water system itself is soluble in water, but forms an oxide film on the surface of the metal, or a film that is insoluble or sparingly soluble in water, to elute metal ions or reduce dissolved oxygen. Inhibits the corrosion reaction by preventing the reaction.
[0004]
As anticorrosive agents, heavy metal salts such as chromates and zinc salts, (poly) phosphates, organic phosphorus compounds and the like are generally used.
[0005]
Furthermore, oxycarboxylic acids such as citric acid and tartaric acid have been proposed.
[0006]
[Problems to be solved by the invention]
Among these conventionally used anticorrosives, chromate has an excellent anticorrosive effect, but has a drawback that local corrosion tends to occur when used at a low concentration. In addition, chromate is highly toxic and its discharge is strictly regulated, so wastewater treatment and recovery treatment are indispensable. Zinc salts have some problems in terms of the anticorrosion effect, and if they flow as wastewater, there are regulatory problems.
[0007]
Furthermore, since phosphate causes the occurrence of red tides, the discharge of phosphorus has recently been regulated from the viewpoint of preventing eutrophication in closed waters.
[0008]
For this reason, at present, there is a strong demand for the emergence of a method capable of suppressing the corrosion of metals such as steel materials in contact with an aqueous system without causing environmental pollution problems such as toxicity and eutrophication.
[0009]
On the other hand, oxycarboxylic acids also contain no regulatory substances, but they have the disadvantage that they are easily decomposed by microorganisms and cannot maintain the anticorrosive effect.
[0010]
An object of the present invention is to solve the above-described conventional problems and to provide a corrosion prevention method that effectively prevents or suppresses corrosion of a metal in contact with an aqueous system without causing environmental pollution problems.
[0011]
[Means for Solving the Problems]
In the anticorrosion method of the present invention, tungstic acid and / or a salt thereof and a water-soluble silicate are respectively added to an aqueous system containing calcium ions in a weight ratio of W: SiO 2 : 11: 1 to 1: 2. And a carboxylic acid-based low molecular weight polymer added to the aqueous system , wherein the carboxylic acid-based low molecular weight polymer is a polyacrylic acid having a molecular weight of 500 to 100,000 and 3- It is a copolymer with allyloxy-2-hydroxypropanesulfonic acid .
[0012]
Conventionally, it is known to use tungstate or water-soluble silicate as an aqueous metal corrosion inhibitor. However, although tungstate has a good anticorrosion effect, it is relatively expensive, so there is a limit to its practical use. On the other hand, water-soluble silicate is relatively inexpensive, but has a weak anticorrosion effect, and does not provide a sufficient anticorrosion effect at practical concentrations, and cannot be said to be a good anticorrosive.
[0013]
As a result of intensive studies on the characteristics of such tungstates and water-soluble silicates, the present inventors have found that in the presence of a specific amount of tungstic acid or a salt thereof and a water-soluble silicate, As a result, it was found that an excellent synergistic effect was achieved and an excellent anticorrosive effect could be obtained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the anticorrosion method of the present invention will be described in detail.
[0015]
In the method of the present invention, tungstic acid and / or a tungstate and a water-soluble silicate are added as an anticorrosive agent to a water system to be treated such as an open cooling water system, a sealed cooling water system, or a brine water system.
[0016]
Examples of tungstate include known water-soluble salts of tungstic acid such as sodium salt, potassium salt and ammonium salt.
[0017]
Examples of the water-soluble silicate include alkali metal salts of silicic acid, and the alkali metal is preferably sodium or potassium from the viewpoint of economy and toxicity. When sodium silicate is used, its Na 2 O / SiO 2 (weight ratio) is preferably 4/1 to 1/4, particularly preferably 1/1 to 1/4.
[0018]
With respect to tungstic acid and / or a salt thereof as well as a water-soluble silicate, one kind may be used alone, or two or more kinds may be used in combination.
[0019]
The ratio of these tungstic acids and / or tungstates to water-soluble silicates is the weight ratio of W in tungstic acid and / or tungstates to SiO 2 in water-soluble silicates: W: SiO 2 = 11: 1 to 1: 2, preferably W: SiO 2 = 3: 1 to 1: 1.4. With such a blending ratio, a remarkably high anticorrosion effect can be obtained due to a very good synergistic effect.
[0020]
In the present invention, tungstic acid and / or tungstate and water-soluble silicate are present in the water system to be treated so as to have the above blending ratio, and the addition form is not particularly limited. These active ingredients may be added to the aqueous system in advance, or may be added separately and mixed in the aqueous system. When a predetermined amount of water-soluble silicate is present in the aqueous system in advance, only tungstic acid or a salt thereof may be added.
[0021]
The use concentration of these active ingredients is determined according to the properties of the water system to be treated and the degree of the corrosive environment, but generally, tungstic acid and / or tungstate and water-soluble silicate in the water system are used. The total concentration is preferably 500 to 5000 mg / L, particularly preferably 100 to 2000 mg / L.
[0022]
In the present invention, the pH of the aqueous system to be treated is preferably 7.5 to 10.0. That is, even if the pH of the aqueous system is less than 7.5 or more than 10.0, the corrosion prevention effect is lowered, and in any case, a good anticorrosion effect cannot be obtained. Therefore, when the pH of the aqueous system is out of the range of 7.5 to 10.0, prior to treatment by the method of the present invention, an alkali such as NaOH and KOH, HCl, H 2 SO It is preferable to adjust the pH of the aqueous system to the above range by adding an acid such as 4 .
[0023]
In addition, the presence of calcium ions in the aqueous system to be treated is not preferable because a precipitate of calcium tungstate is generated. Therefore, in order to prevent the precipitation of calcium tungstate, a carboxylic acid-based low molecular weight polymer is allowed to coexist in the aqueous system. As such a low molecular weight polymer, a copolymer of polyacrylic acid and 3-allyloxy-2-hydroxypropanesulfonic acid (HAPS) having a molecular weight of 500 to 100,000 is used , and the addition amount depends on the aqueous calcium hardness. Although it is different, it is preferable that the addition amount (mg / L) be 1/1000 to 2 times the calcium hardness (CaCO 3 conversion: mg / L).
[0024]
In the present invention, a sufficient anticorrosive effect can be obtained by the above active ingredients, but if necessary, other anticorrosive agents, for example, thiazoles such as mercaptobenzothiazole; azoles such as benzotriazole; hydrazines; Water-soluble amines such as cyclohexylamine, alkylamine, alkanolamine, and polyamine; imines such as ethyleneimine, pyrrolidine, piperidine, piperazine, and ketimine; hydroxamic acids such as formhydroxamic acid, acetohydroxamic acid, and penzhydroxamic acid; catechols Tannins, lignins, phosphonic acids, organic compounds such as oxycarboxylic acids, nitrites, various phosphates, borates, zinc salts, nickel salts, aluminum salts, aluminates, molybdates, vanadium salts, etc. Inorganic salts, etc. Kale inhibitors, may be used in combination slime removal agent, and the like.
[0025]
【Example】
Furthermore it specifically described by taking a real Kenrei the present invention below.
[0026]
Experimental Examples 1-4, Comparative Experimental Examples 1-6
In pure water, 30 mg / L (as CaCO 3 ) with calcium chloride solution, 50 mg / L (as CaCO 3 ) with sodium bicarbonate solution, 30 mg / L (asCaCO 3 ) with magnesium sulfate solution, 50 mg / L with sodium chloride solution 50 mg / L (as SO 4 2− ) was added as a test solution using (asCl − ) and sodium sulfate solution. The pH of this test solution was 7.
[0027]
Take 1 L of the obtained test solution in a 1 L beaker, add various chemicals shown in Table 1 (no addition in Comparative Example 1), immerse one mild steel test piece in each solution, 160 r. p. m. Rotational corrosion test was conducted to investigate the corrosion rate, and the results are shown in Table 1.
[0028]
[Table 1]
From Table 1, according to the present invention, by using both tungstate and water-soluble silicate, the synergistic effect of excellent anticorrosive action at an addition concentration lower than the addition concentration when each agent is added alone. Is clearly obtained.
[0030]
Experimental Examples 5-12, Comparative Experimental Examples 7-10
A solution in which primary ethylene glycol is dissolved in pure water at a ratio of 30% by volume is used, 30 mg / L (as CaCO 3 ) in calcium chloride solution, 82 mg / L (as as sodium hydrogen carbonate solution)
CaCO 3 ), 500 mg / L (as
Cl − ) and 500 mg / L (as SO 4 2− ) were added as a sodium sulfate solution to prepare a test solution.
[0031]
In this test solution, a mild steel test piece (SPCC 31 cm 2 ) was immersed for 3 days at 30 ° C. without adding any chemicals to create a rusted surface in advance, and then various chemicals shown in Table 2 were added (Comparative Experimental Example) 7 was not added), and the pH was adjusted to 7 and then 180 r. p. m. Rotational corrosion test was conducted to examine the corrosion weight loss, and the results are shown in Table 2. In addition, the corrosion weight loss at the time of performing formation of the rusted surface for 3 days in the state of no additive added was 93 mg.
[0032]
[Table 2]
From Table 2, it is clear that the combination of the tungstate and the water-soluble silicate provides an excellent anticorrosion effect that cannot be obtained by adding each agent alone even on the rusted surface.
[0034]
Experimental Example 13
Sodium tungstate dihydrate, low molecular weight polymer (copolymer of acrylic acid and 3-allyloxy-2-hydroxypropanesulfonic acid, molecular weight 5000), sodium silicate (sodium silicate No. 3) and NaOH. Add to deionized water, sodium tungstate 15 parts by weight, low molecular weight polymer 1 part by weight, sodium silicate 33 parts by weight, NaOH 3 parts by weight, water 48 parts by weight, pH 13 anticorrosive composition (sodium tungstate and silicic acid W conversion with sodium: SiO 2 conversion weight ratio is 8:10), and this anticorrosive composition is allowed to stand in an incubator at room temperature and 60 ° C. After 3 months, precipitates, precipitates, appearance changes The presence or absence was observed, and the results are shown in Table 3.
[0035]
[Table 3]
From Table 3, it can be seen that the anticorrosive composition containing tungstate, water-soluble silicate and low molecular weight polymer is excellent in product stability even when blended as one agent.
[0037]
Experimental Example 14
In deionized water, calcium carbonate, NaOH as a pH adjusting agent, sodium tungstate dihydrate, low molecular weight polymer (copolymer of acrylic acid and 3-allyloxy-2-hydroxypropanesulfonic acid, molecular weight 5000 ) And sodium silicate (sodium silicate No. 3) are added so as to have the following concentration and water quality, and a test solution is prepared and left at 50 ° C. for 40 hours, and then the pH, calcium hardness, The sodium tungstate concentration and appearance were examined and the results are shown in Table 4.
[0038]
[Test solution]
Calcium hardness: 50 mg / L (as CaCO 3 )
M alkalinity: 100 mg / L (as CaCO 3 )
pH: 8.0
Sodium tungstate: 150 mg / L (as W)
Low molecular weight polymer: 0, 10, 20, 30 or 60 mg / L
Sodium silicate: 100 mg / L (as SiO 2 )
[0039]
[Table 4]
Table 4 shows that calcium tungstate precipitates and the tungstate is consumed in the presence of calcium ions, but precipitation of calcium tungstate can be prevented by addition of a low molecular weight polymer.
[0041]
Experimental Example 15
In pure water, a calcium chloride solution is 50 mg / L (asCaCO 3 ), a sodium hydrogen carbonate solution is 50 mg / L (asCaCO 3 ), a sodium chloride solution is 50 mg / L (asCl − ), and a sodium sulfate solution is 50 mg / L (asSO 4 -) was added to the test solution. Furthermore, NaOH was added so that it might become 3000 mg / L. Carbon dioxide gas was blown into the system controlled by a pH stat, and during the test period, the pH was 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10. Kept at 5.
[0042]
Sodium tungstate 50 mg / L (as W) and sodium silicate (sodium silicate No. 3) 25 mg / L (as SiO 2 ) were added to each test solution, and one mild steel test piece was immersed in each test solution. At 160 ° C. for 5 days at 50 ° C. p. m. Rotational corrosion test was conducted and the corrosion rate was examined. The results are shown in Table 5.
[0043]
[Table 5]
From Table 5, when the pH of the aqueous system is less than 7.5 or exceeds 10.0, a sufficient anticorrosive effect cannot be obtained, and in the present invention, the pH of the aqueous system is in the range of 7.5 to 10.0. It turns out that it is preferable to do.
[0045]
【The invention's effect】
As described above in detail, the anticorrosion method of the present invention is one in which a specific proportion of tungstic acid and / or tungstate and water-soluble silicate is present in the aqueous system, and is excellent by two active ingredients. Due to the synergistic effect, a remarkably high anticorrosion effect is obtained, and an excellent anticorrosion inhibition or prevention effect is exerted on metals such as steel materials that come into contact with water.
[0046]
According to the present invention, since a sufficient effect can be obtained with a small amount of drug used, the anticorrosion treatment cost can be reduced, and an excellent anticorrosive effect can be achieved even on a rusted surface. Furthermore, since no heavy metal salt is contained in the waste water, there is no problem of toxicity, and since it does not contain phosphorus and has low COD, there is no problem of eutrophication.
[0047]
For this reason, according to the present invention, metal corrosion can be effectively prevented without causing environmental pollution problems.
Claims (4)
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| JP7163949B2 (en) | 2019-11-28 | 2022-11-01 | Ｊｆｅスチール株式会社 | Surface treated steel plate |
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| KR101606357B1 (en) | 2013-03-27 | 2016-03-25 | 쿠리타 고교 가부시키가이샤 | Method and agent for treating water in cooling water system |
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