JPH0248629B2 - TETSUKEIKINZOKUNOFUSHOKUBOSHIHOHO - Google Patents

TETSUKEIKINZOKUNOFUSHOKUBOSHIHOHO

Info

Publication number
JPH0248629B2
JPH0248629B2 JP22656387A JP22656387A JPH0248629B2 JP H0248629 B2 JPH0248629 B2 JP H0248629B2 JP 22656387 A JP22656387 A JP 22656387A JP 22656387 A JP22656387 A JP 22656387A JP H0248629 B2 JPH0248629 B2 JP H0248629B2
Authority
JP
Japan
Prior art keywords
corrosion
water
iron
tin
film
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
JP22656387A
Other languages
Japanese (ja)
Other versions
JPS6473093A (en
Inventor
Masamitsu Ikeuchi
Yoshiaki Shibuya
Katsuhiro Okaguchi
Eishin Okazaki
Yukako Iwasaki
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AKUASU KK
Original Assignee
AKUASU KK
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by AKUASU KK filed Critical AKUASU KK
Priority to JP22656387A priority Critical patent/JPH0248629B2/en
Publication of JPS6473093A publication Critical patent/JPS6473093A/en
Publication of JPH0248629B2 publication Critical patent/JPH0248629B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/60Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using alkaline aqueous solutions with pH greater than 8
    • C23C22/62Treatment of iron or alloys based thereon

Landscapes

  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)

Description

【発明の詳細な説明】[Detailed description of the invention]

(発明の目的) 産業上の利用分野 本発明は水と接触する各種機器の金属面を防食
する方法に関し、更に詳しくはボイラ、熱交換
器、配管系などにおける鉄系金属の表面を耐食化
する方法に関する。 従来の技術 鉄系金属によつて製作された機器等が水と接触
して使用される場合、表面が腐食して機器等の機
能を損い、あるいは寿命を縮めるなどの問題がお
こる。かかる水による鉄系金属面の腐食の主な因
子は水のPHと溶存酸素であり、特にボイラなど高
温の水系を取扱う機器においては特に著しい影響
を有している。 このような金属面に対する腐食因子を除くため
には、特別な場合を除き薬剤の添加による化学的
処理方法が採用されることが普通である。すなわ
ち、PHに関しては、金属材料の材質や使用される
環境条件に応じて、それぞれ腐食速度が最小とな
る範囲内に入るよう制御することが行われ、たと
えばボイラなど高温水系の機器に使用される鉄系
金属材料ではPHが11ないし12の範囲で腐食速度が
小さくなるところから、水中に水酸化ナトリウム
や炭酸ナトリウムなどのアルカリ性薬剤を添加し
て、PHをこの範囲内に保つように管理するのが普
通である。 また、溶存酸素については、ヒドラジンや亜硫
酸ナトリウムなどの還元剤を用いて水の脱酸素を
行なう方法があるが、水には空気中の酸素が溶け
込むため還元剤を消耗に応じて補給することが必
要である。 一方、鉄の表面は100℃以上の温度領域におい
て水と反応し、シツコール(schikorr)反応によ
つてマグネタイト(Fe3O4)の皮膜を形成し、耐
食性となることが知られている。 Fe→Fe2++2e- Fe2++2OH-→Fe(OH)2 3Fe(OH)2→Fe3O4+H2+2H2O しかし、この反応は200℃以上の高温領域にお
いては比較的速やかに起るが、それ以下の温度で
は反応速度が遅く、長時間かからないと充分に防
食性のあるマグネタイト皮膜が形成されない。そ
してこの際に、水中に溶存酸素があるときには酸
素と水酸化第1鉄とが反応して水酸化第2鉄とな
り、マグネタイト皮膜の形成が妨げられるという
問題がある。 4Fe(OH)2+O2+2H2O→4Fe(OH)3 このような事情にあつて、鉄系金属表面に安定
な耐食性皮膜を速やかに形成させるため、アルカ
リ性化剤と還元剤とを水中に添加して高温処理す
ることが行なわれているが、かかる薬剤は使用量
が少いと効果が少なく、またボイラ水などで薬剤
の濃縮が行なわれると孔食発生などの原因ともな
る危険性がある。そして更に、200℃以上のよう
な充分に高い温度でないと安定で強い防食皮膜が
形成されず、100〜200℃では不安定で破壊され易
い防食皮膜となり易いという問題があつた。 発明が解決しようとする問題点 以上のことから、鉄系金属の表面に200℃以上
のような高温度でなくても短時間の処理によつて
安定な防食皮膜を確実に形成するための方法が望
まれており、本発明はかかる要望にこたえうるよ
うな防食皮膜を形成することにより鉄系金属の腐
食を防止する方法を提供しようとするものであ
る。 (発明の構成) 問題点を解決するための手段 本発明者らは、前記の問題点を解決するために
鋭意研究を進めた結果、鉄系金属が特定範囲内の
PH値を有する2価のスズ塩水溶液に接触すると、
金属表面に酸化第2スズの層が形成されると同時
にこの酸化第2スズを含む強固な防食皮膜が生成
することを見出し、本発明を完成するに至つた。
すなわちかかる本発明は、2価のスズ塩を含有す
る水溶液であつてそのPHが次の式()、()お
よび() PH≧10.5 () PH≧2.8log10〔Sn〕+19 () PH≧−9.8log10〔Sn〕−25 () ただし〔Sn〕は2価のスズのモル濃度(mol/
)を示す。 を同時に満足する範囲内にあるものを、反応温度
下において鉄系金属表面に接触させることを特徴
とする鉄系金属の防食防止方法である。 このような2価のスズの濃度とPHとの関係を第
1図に示すが、図における3本の線に囲まれた斜
線を付した領域が、本発明の実施に適した範囲を
表わしている。 本発明において、水溶液中に含有される2価の
スズ塩は水中に溶解していればよく、スズイオン
であつてもよくまた錯イオンであつても構わな
い。かかるスズ塩としては塩化第1スズ、硫酸第
1スズ、硝酸第1スズなどが挙げられるが、アル
カリ金属の亜スズ酸塩などであつてもよく、特に
限定されない。 また反応温度は100℃以上であるのがよく、更
には150℃以上であるのが一層好ましい。 本発明の方法を実施するに当つてスズイオンと
鉄系金属表面の反応を阻害しない限り、適宜の薬
剤等を併用してもよいことは勿論である。 実施例 東京都水から得た第1表に示す性状の脱アルカ
リ軟水にそれぞれ所定のスズ濃度となるように塩
化第1スズ2水塩を添加し、水酸化カリウムを用
いて所定のPHとなるように調整して、それぞれ試
験水を得た。 内容積3のオートクレーブにそれぞれ試験水
を入れ、この中にみがき軟鋼板の試験片(30mm×
15mm×2mm)を吊して取り付け、密閉後、撹拌し
ながら170℃で48時間加熱処理し、反応させた。
処理終了後試験片を取り出して、外観ならびに孔
食の有無を調べた。その結果は第2表に示す。 本発明の方法によつて処理された試験片の表面
は青〜黒色に着色しており、その表面をX線回折
により調べたところ鉄と共に二酸化スズを含む皮
膜が生成していることがわかつた。更に、表面皮
膜についてオージエ電子分光分析を行なつたとこ
ろ、鉄を含むスズの酸化物皮膜であることが確か
められた。 次に、前記と同じ脱アルカリ軟水に亜硝酸ナト
リウム1mg/、グルコース15mg/、および水
酸化カリウム10mg/を添加調製した腐食試験水
1中に、前記の処理済み試験片を吊し、開放下
に撹拌しながら40℃で72時間浸漬して腐食試験を
行なつた。一方、ブランク試験として未処理の軟
鋼板の試験片についても全く同様に腐食試験を行
なつた。このような試験により、それぞれ腐食速
度(mdd:1dm21日当りの腐食減量mg)を求め、
次の計算式 防食率=ブランクのmdd−サンプルのmdd/ブランクのmd
d×100 によつて防食率を算出した。 これらの腐食試験の結果も、合わせて第2表に
示す。
(Purpose of the Invention) Industrial Application Field The present invention relates to a method for corrosion-proofing the metal surfaces of various equipment that come into contact with water, and more specifically to a method for corrosion-proofing the surfaces of ferrous metals in boilers, heat exchangers, piping systems, etc. Regarding the method. BACKGROUND OF THE INVENTION When equipment made of ferrous metals is used in contact with water, problems such as surface corrosion may occur, impairing the functionality of the equipment or shortening its lifespan. The main factors causing corrosion of ferrous metal surfaces by water are the pH of the water and dissolved oxygen, which have a particularly significant effect on equipment that handles high-temperature water systems, such as boilers. In order to remove such corrosive factors from metal surfaces, chemical treatment methods involving the addition of chemicals are usually employed, except in special cases. In other words, PH is controlled to be within a range that minimizes the corrosion rate depending on the material of the metal material and the environmental conditions in which it is used. For example, when used in high-temperature water-based equipment such as boilers, Since the corrosion rate of iron-based metal materials decreases when the pH is in the range of 11 to 12, it is necessary to add alkaline agents such as sodium hydroxide or sodium carbonate to the water to maintain the pH within this range. is normal. Regarding dissolved oxygen, there is a method of deoxygenating water using a reducing agent such as hydrazine or sodium sulfite, but since oxygen in the air dissolves in water, it is necessary to replenish the reducing agent as it is consumed. is necessary. On the other hand, it is known that the surface of iron reacts with water in a temperature range of 100°C or higher, forming a film of magnetite (Fe 3 O 4 ) through the schikorr reaction, resulting in corrosion resistance. Fe→Fe 2+ +2e - Fe 2+ +2OH - →Fe(OH) 2 3Fe(OH) 2 →Fe 3 O 4 +H 2 +2H 2 O However, this reaction occurs relatively quickly in the high temperature range of 200℃ or higher. However, at lower temperatures, the reaction rate is slow and a magnetite film with sufficient anti-corrosion properties will not be formed unless it takes a long time. At this time, there is a problem that when there is dissolved oxygen in the water, oxygen and ferrous hydroxide react to form ferric hydroxide, which prevents the formation of a magnetite film. 4Fe(OH) 2 +O 2 +2H 2 O→4Fe(OH) 3 Under these circumstances, in order to quickly form a stable corrosion-resistant film on the surface of iron-based metals, an alkalizing agent and a reducing agent are added to the water. Addition of such chemicals to high-temperature treatment has been carried out, but such chemicals are less effective if used in small amounts, and if concentrated in boiler water, etc., there is a risk of causing pitting corrosion. . Furthermore, there is a problem that a stable and strong anti-corrosion film cannot be formed unless the temperature is sufficiently high, such as 200°C or higher, and that the anti-corrosion film is unstable and easily destroyed at 100 to 200°C. Problems to be Solved by the Invention Based on the above, we have developed a method for reliably forming a stable anti-corrosion film on the surface of iron-based metals in a short period of time, even if the temperature is not as high as 200°C or higher. The present invention aims to provide a method for preventing corrosion of iron-based metals by forming an anti-corrosion film that can meet such demands. (Structure of the Invention) Means for Solving the Problems As a result of intensive research to solve the above-mentioned problems, the present inventors have discovered that iron-based metals fall within a specific range.
When it comes into contact with a divalent tin salt aqueous solution having a PH value,
The present inventors have discovered that a strong anticorrosive film containing this tin oxide is formed at the same time as a layer of stannic oxide is formed on a metal surface, leading to the completion of the present invention.
That is, the present invention is an aqueous solution containing a divalent tin salt, the pH of which is expressed by the following formulas (), (), and () PH≧10.5 () PH≧2.8log 10 [Sn] + 19 () PH≧ −9.8log 10 [Sn] −25 () However, [Sn] is the molar concentration of divalent tin (mol/
) is shown. This is a method for preventing corrosion of iron-based metals, which is characterized in that a material that is within a range that satisfies the following is brought into contact with the surface of iron-based metals at a reaction temperature. The relationship between the concentration of divalent tin and PH is shown in FIG. 1, and the shaded area surrounded by three lines in the figure represents the range suitable for implementing the present invention. There is. In the present invention, the divalent tin salt contained in the aqueous solution only needs to be dissolved in water, and may be a tin ion or a complex ion. Such tin salts include stannous chloride, stannous sulfate, stannous nitrate, etc., but are not particularly limited and may also be stannous salts of alkali metals. Further, the reaction temperature is preferably 100°C or higher, more preferably 150°C or higher. It goes without saying that when carrying out the method of the present invention, appropriate agents may be used in combination as long as they do not inhibit the reaction between the tin ions and the surface of the iron-based metal. Example: To dealkalized soft water obtained from Tokyo Metropolitan Water and having the properties shown in Table 1, stannous chloride dihydrate was added to the specified tin concentration, and potassium hydroxide was used to adjust the pH to the specified value. Test water was obtained by adjusting the water as follows. Pour test water into each autoclave with an internal volume of 3, and place a test piece of polished mild steel plate (30 mm x
15 mm x 2 mm) was hung and sealed, and then heat treated at 170°C for 48 hours with stirring to react.
After the treatment was completed, the test pieces were taken out and examined for appearance and presence of pitting corrosion. The results are shown in Table 2. The surface of the specimen treated by the method of the present invention was colored blue to black, and when the surface was examined by X-ray diffraction, it was found that a film containing tin dioxide as well as iron was formed. . Further, when the surface film was subjected to Auger electron spectroscopy, it was confirmed that it was a tin oxide film containing iron. Next, the treated test piece was suspended in corrosion test water 1, which was prepared by adding 1 mg of sodium nitrite, 15 mg of glucose, and 10 mg of potassium hydroxide to the same dealkalized soft water as above, and left it open. Corrosion tests were conducted by immersing at 40°C for 72 hours with stirring. On the other hand, as a blank test, a corrosion test was conducted on a test piece of an untreated mild steel plate in exactly the same manner. Through these tests, the corrosion rate (mdd: corrosion loss mg per 1dm 2 per day) was determined.
The following calculation formula: Corrosion protection rate = mdd of blank - mdd of sample / md of blank
Corrosion protection rate was calculated by d×100. The results of these corrosion tests are also shown in Table 2.

【表】【table】

【表】【table】

【表】【table】

【表】 * 比較例
** 未処理鋼板の腐食試験20個の
平均値
以上の結果をみると、本発明の方法によつて鉄
系金属の表面を処理することにより、すぐれた耐
食性が得られることがわかる。 (発明の効果) 本発明は、2価のスズ塩を含む水溶液であつて
そのPHが2価のスズのモル濃度に対して特定の範
囲内にあるものと接触させることによつて鉄系金
属の表面にすぐれた耐食性を付与するものであ
り、短時間で確実に安定な防食皮膜を形成できる
特長を有する。
[Table] * Comparative example
** Average value of 20 corrosion tests on untreated steel sheets The above results show that excellent corrosion resistance can be obtained by treating the surface of ferrous metals by the method of the present invention. (Effects of the Invention) The present invention is capable of treating iron-based metals by bringing them into contact with an aqueous solution containing a divalent tin salt, the pH of which is within a specific range relative to the molar concentration of divalent tin. It imparts excellent corrosion resistance to the surface of the metal, and has the feature of being able to reliably form a stable anti-corrosion film in a short period of time.

【図面の簡単な説明】[Brief explanation of drawings]

第1図は、本発明の鉄系金属の腐食防止方法に
用いられる処理用水溶液のスズの濃度とPHとに必
要とされる範囲を示すグラフである。
FIG. 1 is a graph showing the range required for the tin concentration and pH of the aqueous treatment solution used in the method for preventing corrosion of iron-based metals of the present invention.

Claims (1)

【特許請求の範囲】 1 2価のスズ塩を含有する水溶液であつてその
PHが下記の式()、()および() PH≧10.5 () PH≧2.8log10〔Sn〕+1.9 () PH≧−9.8log10〔Sn〕−25 () ただし〔Sn〕は2価のスズのモル濃度(mol/
)を示す。 を同時に満足する範囲内にあるものを、反応温度
下において鉄系金属表面に接触させることを特徴
とする、鉄系金属の腐食防止方法。 2 反応温度が100℃以上である、特許請求の範
囲第1項記載の鉄系金属の腐食防止方法。
[Claims] 1. An aqueous solution containing a divalent tin salt, which
PH is the following formula (), () and () PH≧10.5 () PH≧2.8log 10 [Sn]+1.9 () PH≧−9.8log 10 [Sn]−25 () However, [Sn] is 2 molar concentration of tin (mol/
) is shown. 1. A method for preventing corrosion of ferrous metals, the method comprising bringing a substance within a range that simultaneously satisfies the following into contact with the surface of ferrous metals at a reaction temperature. 2. The method for preventing corrosion of ferrous metals according to claim 1, wherein the reaction temperature is 100°C or higher.
JP22656387A 1987-09-11 1987-09-11 TETSUKEIKINZOKUNOFUSHOKUBOSHIHOHO Expired - Lifetime JPH0248629B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP22656387A JPH0248629B2 (en) 1987-09-11 1987-09-11 TETSUKEIKINZOKUNOFUSHOKUBOSHIHOHO

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP22656387A JPH0248629B2 (en) 1987-09-11 1987-09-11 TETSUKEIKINZOKUNOFUSHOKUBOSHIHOHO

Publications (2)

Publication Number Publication Date
JPS6473093A JPS6473093A (en) 1989-03-17
JPH0248629B2 true JPH0248629B2 (en) 1990-10-25

Family

ID=16847118

Family Applications (1)

Application Number Title Priority Date Filing Date
JP22656387A Expired - Lifetime JPH0248629B2 (en) 1987-09-11 1987-09-11 TETSUKEIKINZOKUNOFUSHOKUBOSHIHOHO

Country Status (1)

Country Link
JP (1) JPH0248629B2 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7964044B1 (en) * 2003-10-29 2011-06-21 Birchwood Laboratories, Inc. Ferrous metal magnetite coating processes and reagents

Also Published As

Publication number Publication date
JPS6473093A (en) 1989-03-17

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