JPS595661B2 - Al alloy with excellent pitting corrosion resistance - Google Patents

Al alloy with excellent pitting corrosion resistance

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Publication number
JPS595661B2
JPS595661B2 JP53079806A JP7980678A JPS595661B2 JP S595661 B2 JPS595661 B2 JP S595661B2 JP 53079806 A JP53079806 A JP 53079806A JP 7980678 A JP7980678 A JP 7980678A JP S595661 B2 JPS595661 B2 JP S595661B2
Authority
JP
Japan
Prior art keywords
alloy
pitting corrosion
corrosion resistance
corrosion
pitting
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
Application number
JP53079806A
Other languages
Japanese (ja)
Other versions
JPS558426A (en
Inventor
庸 竹内
建 当摩
一夫 戸田
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.)
Mitsubishi Metal Corp
Original Assignee
Mitsubishi Metal Corp
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 Mitsubishi Metal Corp filed Critical Mitsubishi Metal Corp
Priority to JP53079806A priority Critical patent/JPS595661B2/en
Publication of JPS558426A publication Critical patent/JPS558426A/en
Publication of JPS595661B2 publication Critical patent/JPS595661B2/en
Expired legal-status Critical Current

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Description

【発明の詳細な説明】 この発明は、すぐれた押出加工性および適度の強度を有
し、さらに特にすぐれた耐孔食性を有するA1合金に関
するものである。
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an A1 alloy that has excellent extrudability and moderate strength, and particularly has excellent pitting corrosion resistance.

従来、一般に、押出加工性にすぐれ、かつ適度の強度を
有するA1合金として、例えばAA規格の6000番代
のA1合金が知られている。
BACKGROUND ART Conventionally, as an A1 alloy having excellent extrusion processability and moderate strength, for example, an A1 alloy in the 6000 series of AA standard is known.

このAA規格6000番代の従来A1合金は、時効処理
によって素地中に析出した微細なMg2Si化合物の存
在によって適度の強度とすぐれた押出加工性をもつよう
になるものであって、建築などにおける各種構造物材料
として広(使用されているものである。
This conventional A1 alloy of the AA standard 6000 series has moderate strength and excellent extrusion processability due to the presence of fine Mg2Si compounds precipitated in the base material by aging treatment, and is used in various applications such as construction. It is widely used as a structural material.

また、この従来A1合金は、陽極酸化などの表面処理性
にもすぐれていることから、特に建築用として使用する
場合には、耐食性や装飾性などを付与する目的で表面処
理が施されることが多い。
In addition, this conventional A1 alloy has excellent surface treatment properties such as anodization, so when it is used for construction, it is often subjected to surface treatments to impart corrosion resistance and decorative properties. There are many.

さらに、この従来A1合金は、A1合金の中でもAl−
Mg系およびAI −Mn系などのA1合金に次いで比
較的良好な耐食性をもつことから、使用環境が例えば中
性の水溶液である場合などでは、上記のような表面処理
を施さない状態、すなわち素材のままの状態で使用して
も、その表面に形成される安定な不働態皮膜によって十
分な耐食性を示すものであり、すぐれた押出加工性と合
まって、例えば給排水用配管材料などとして用いられて
いる。
Furthermore, this conventional A1 alloy is Al-
It has relatively good corrosion resistance next to A1 alloys such as Mg-based and AI-Mn-based alloys, so when the usage environment is, for example, a neutral aqueous solution, it is possible to use the material without surface treatment as described above. Even when used as is, it exhibits sufficient corrosion resistance due to the stable passive film formed on its surface. Combined with its excellent extrusion processability, it is used, for example, as a piping material for water supply and drainage. ing.

しかし、上記AA規格6000番代の従来A1合金は、
使用環境中にClイオンなどの不働態皮膜を破壊するイ
オン種が含まれている場合には、その表面に孔食を発生
することがあり、さらに重金属イオン、特にCuイオン
が含まれているような使用環境下では、前記Clイオン
などによる孔食が前記CUイオンによって一段と成長し
て貫通孔にまで発展し、重大事故の発生原因となること
がしばしば生じていた。
However, the conventional A1 alloy of the AA standard 6000 series,
If the usage environment contains ionic species that destroy passive films, such as Cl ions, pitting corrosion may occur on the surface, and if heavy metal ions, especially Cu ions, are included. Under such usage environments, the pitting corrosion caused by the Cl ions and the like grows further due to the CU ions and develops into through holes, often causing serious accidents.

このような孔食は、Clイオン濃度が高(、溶液の比抵
抗が小さい海水などの場合よりも、むしろClイオン濃
度が低(、溶液の比抵抗が大きい淡水などの使用環境下
で特に顕著に現われていた。
This kind of pitting corrosion is particularly noticeable in usage environments such as freshwater where the Cl ion concentration is low (and the specific resistance of the solution is high) rather than in environments where the Cl ion concentration is high (and the specific resistance of the solution is low, such as seawater). It appeared in

すなわち、例えば水道水中には、上水道で殺菌消毒用の
サラシ粉が添加されるため、数10ppm以下のClイ
オンが含有されているが、このような低いClイオン濃
度の水道水に上記従来A1合金製部材がさらされると、
前記部材には比較的早期に孔食が発生するようになるの
である。
That is, for example, tap water contains Cl ions of several tens of ppm or less because sterilization powder is added to the tap water. When the manufactured parts are exposed,
Pitting corrosion occurs in the member relatively early.

そこで1、本発明者等は、上述のような観点から、良好
な押出加工性と表面処理性、および適度の強度を有する
AA規格6000番代の従来AI合金に着目し、これら
特性を何ら損うことなく、Clイオンが含まれている水
道水や、Clイオンに加えてCuイオンなどを含有する
水溶液などを取扱う環境、さらにその他のきわめて孔食
の発生しやすい環境において、すぐれた耐孔食性を示す
材料を得べく研究を行なった結果、 (a) 上記従来A1合金においては、押出加工性お
よび強度を確保する目的で、Si:0.2〜1.2%と
、Mg:0.45〜1.5%(重量%、以下%は重量%
を示す)を含有し、かつMgとSiの相対含有量は、素
地中に析出するMg2Si化合物の原子比(2:1)を
基準として、これよりもSiが多少多くなるようになっ
ていて、時効処理後の組織は、Al−8i 固溶体の素
地中にMg2Si化合物が微細に析出した2相組織とな
っており、このMg2Si化合物は素地に比して電気化
学的に卑であるため、こ、の両者の電位差によってミク
ロなガルバニック腐食が生じ易くなっていることが孔食
発生の一因であること。
Therefore, 1. From the above-mentioned viewpoint, the present inventors focused on a conventional AI alloy of the AA standard 6000 series, which has good extrusion processability, surface treatment properties, and moderate strength, and developed a method that does not impair these properties. Excellent pitting corrosion resistance in environments where tap water containing Cl ions, aqueous solutions containing Cu ions in addition to Cl ions, and other environments where pitting corrosion is extremely likely to occur. As a result of research to obtain a material exhibiting ~1.5% (weight%, below % is weight%)
), and the relative content of Mg and Si is such that Si is somewhat larger than the atomic ratio (2:1) of the Mg2Si compound precipitated in the matrix, The structure after aging is a two-phase structure in which Mg2Si compounds are finely precipitated in the Al-8i solid solution matrix, and this Mg2Si compound is electrochemically less noble than the matrix. One reason for pitting corrosion is that micro galvanic corrosion is more likely to occur due to the potential difference between the two.

(b)シたがって、素地とMg2Si化合物間の電位差
を、Mg2Si化合物をより貴にするか、あるいは素地
をより卑にするかして小さくしてやれば、これが小さく
なればなるほどガルバニック腐食が生じにくくなって孔
食発生が抑制されるようになること。
(b) Therefore, if we reduce the potential difference between the substrate and the Mg2Si compound by making the Mg2Si compound more noble or by making the substrate more base, the smaller the potential difference, the less galvanic corrosion will occur. The occurrence of pitting corrosion will be suppressed.

(e) 上記のAl−8i固溶体の素地にMg2Si
化合物が析出した2相組織を有するA1合金に、固溶限
度内の小量のZnを含有させると、前記素地がより卑に
なってMg2Si化合物との電位差が著しく小さなもの
となること。
(e) Mg2Si in the base of the above Al-8i solid solution
When an A1 alloy having a two-phase structure in which a compound is precipitated contains a small amount of Zn within the solid solubility limit, the base material becomes more base and the potential difference with the Mg2Si compound becomes extremely small.

以上a)〜(e)に示される知見を得たのである。The findings shown in a) to (e) above were obtained.

この発明は、上記知見にもとづいてなされたものであっ
て、 Si:0.2〜1.2%、 Mg:0.45〜1.5%、 Zn:0.3〜1%、 を含有し、残りがAIと不可避不純物からなる組成を有
し、かつすぐれた耐孔食性を有し、さらに適度の強度と
良好な押出加工性も具備したA1合金に特徴を有するも
のである。
This invention was made based on the above findings, and contains Si: 0.2 to 1.2%, Mg: 0.45 to 1.5%, and Zn: 0.3 to 1%. The A1 alloy has a composition with the remainder consisting of AI and unavoidable impurities, and has excellent pitting corrosion resistance, as well as moderate strength and good extrusion processability.

つぎに、この発明のA1合金において、成分組成を上記
の通りに限定した理由を説明する。
Next, the reason why the component composition of the A1 alloy of the present invention is limited as described above will be explained.

(a)SiおよびMg これらの成分には、上記の通り素地中に微細に分散析出
するMg2Siを形成して、合金の押出加工性および強
度を向上させる作用があるが、その含有量が、それぞれ
Si:0.2%未満およびMg:0.45%未満では、
前記作用に所望の効果が得られず、一方Si:1.2%
、Mg:1.5%を越えて含有させると、合金の靭性が
急激に低下するようになることから、その含有量を、そ
れぞれSi:0.2〜1.2%、Mg二0.45〜1.
5%と定めた。
(a) Si and Mg As mentioned above, these components have the effect of forming Mg2Si that is finely dispersed and precipitated in the matrix to improve the extrusion workability and strength of the alloy. Si: less than 0.2% and Mg: less than 0.45%,
The desired effect was not obtained in the above action, while Si: 1.2%
, Mg: If the content exceeds 1.5%, the toughness of the alloy will decrease rapidly. ~1.
It was set at 5%.

(b) Zn Zn成分には、素地に固溶して、これを電気化学的に卑
にし、もって素地とMg2Si化合物との間に電位差が
存在しないようにして、ガルバニック腐食を極力抑制す
る一方、合金表面に形成される自然酸化皮膜の生成を適
度に弱めて全面腐食をわずかに促進させ、もって孔食発
生を著しく抑制する作用があるが、その含有量が0.3
%未満では耐孔食性を得ることができず、一方1%を越
えて含有させると、全面腐食が著しく増大するようにな
ると共に、不均一腐食も発生するようになることから、
その含有量を0.3〜1%と定めた。
(b) Zn The Zn component is dissolved in the base material to make it electrochemically base, so that there is no potential difference between the base material and the Mg2Si compound, and galvanic corrosion is suppressed as much as possible. It has the effect of moderately weakening the natural oxide film that forms on the alloy surface and slightly promoting general corrosion, thereby significantly suppressing the occurrence of pitting corrosion, but its content is 0.3
If the content is less than 1%, pitting corrosion resistance cannot be obtained, while if the content exceeds 1%, overall corrosion will increase significantly and uneven corrosion will also occur.
Its content was determined to be 0.3 to 1%.

なお、この発明のA1合金においては、上記の通りZn
を含有するにもかかわらず、Znを含有しない場合と同
等の表面処理性をもつので、陽極酸化などの表面処理を
良好に施すことができるのである。
In addition, in the A1 alloy of this invention, as mentioned above, Zn
Despite containing Zn, it has surface treatment properties equivalent to those not containing Zn, so surface treatments such as anodic oxidation can be performed satisfactorily.

つぎに、この発明のA1合金を実施例により具体的に説
明する。
Next, the A1 alloy of the present invention will be specifically explained using examples.

実施例 通常の溶解法により、それぞれ第1表に示される成分組
成をもったA1合金溶湯を調製した後、インゴットに鋳
造し、ついで通常の条件にて均熱化処理、熱間圧延、お
よび冷間圧延を施して板厚:1mmの板材とし、引続い
てこの板材に、温度:550℃に1時間保持後空冷の溶
体化処理と、温度:160℃に24時間保持の時効処理
を施すことによって本発明A1合金1〜3、およびZn
含有量がこの発明の範囲から外れた比較A1合金1゜2
の板材をそれぞれ製造した。
EXAMPLE After preparing A1 alloy molten metals having the compositions shown in Table 1 by the usual melting method, they were cast into ingots, and then subjected to soaking treatment, hot rolling, and cooling under normal conditions. The plate material is rolled to a thickness of 1 mm, and then this plate material is subjected to solution treatment by holding at a temperature of 550°C for 1 hour and then air cooling, and aging treatment by holding at a temperature of 160°C for 24 hours. According to the present invention A1 alloys 1 to 3, and Zn
Comparative A1 alloy 1°2 whose content is outside the range of this invention
Each plate material was manufactured.

つぎに、この結果得られた本発明A1合金1〜3および
比較A1合金1.2の板材について、CuCl2・2H
20を添加してCuイオン濃度をlppmとした温度:
30℃の水道水と、次亜塩素酸ナトリウムを添加してC
Iイオン濃度を30ppmとした水道水を用い、これら
両水道水中にそれぞれ1ケ月浸漬の試験を行ない、試験
後、クロム酸系溶液で腐食生成物を除去して、腐食減量
、孔食数、および最大孔食深さをそれぞれ測定した。
Next, CuCl2・2H
Temperature at which Cu ion concentration was set at lppm by adding 20:
C by adding tap water at 30℃ and sodium hypochlorite.
Using tap water with an I ion concentration of 30 ppm, a test was conducted by immersing it in each of these tap waters for one month. After the test, corrosion products were removed with a chromic acid solution, and corrosion weight loss, pitting number, and The maximum pitting depth was measured for each.

これらの測定結果を第1表に示した。The results of these measurements are shown in Table 1.

第1表に示されるように、Cuイオン含有水道水試験に
おいて、本発明A1合金1〜3は、Znを含有しない比
較A1合金1に比して、全面腐食形態をとるため、Zn
の含有量が増加するにしたがって腐食減量が多(なる傾
向を示しているが、孔食数および最大孔食深さは半分以
下になっており、またZn含有量が本発明範囲から高い
方に外れた比較A1合金2においては、Zn含有量が多
いことに原因して腐食減量が多(なると共に、孔食数お
よび最大孔食深さもZnを含有しない比較A1合金1に
ほぼ相当する値を示し、耐孔食性の悪いものであった。
As shown in Table 1, in the Cu ion-containing tap water test, the A1 alloys 1 to 3 of the present invention took the form of general corrosion compared to the comparison A1 alloy 1 that does not contain Zn.
As the Zn content increases, the corrosion loss tends to increase, but the number of pitting corrosion and the maximum pitting depth are less than half, and when the Zn content is higher than the range of the present invention. Comparative A1 Alloy 2, which is out of the range, has a large corrosion loss due to the high Zn content (and the number of pitting corrosion and maximum pitting depth also have values almost equivalent to Comparative A1 Alloy 1, which does not contain Zn). It showed poor pitting corrosion resistance.

また、CIイオン含有水道水試験においても、Cuイオ
ン含有水道水試験と同様な傾向を示しており、本発明A
1合金1〜3には全く孔食発生が見られないことが明ら
かである。
In addition, the CI ion-containing tap water test also showed the same tendency as the Cu ion-containing tap water test, and the present invention A
It is clear that no pitting corrosion is observed in Alloys 1 to 3.

上述のように、この発明のA1合金は、すぐれた押出加
工性と適度な強度を具備した状態で、特にすぐれた耐孔
食性を有しており、例えばCIイオンやCuイオンなど
を含有する水道水などにさらされる苛酷な環境下で使用
してもきわめてすぐれた耐孔食性を示すのである。
As mentioned above, the A1 alloy of the present invention has excellent extrusion processability and moderate strength, and has particularly excellent pitting corrosion resistance. It exhibits excellent pitting corrosion resistance even when used in harsh environments where it is exposed to water.

Claims (1)

【特許請求の範囲】 lsi:0.2〜1.2%、 Mg:0.45〜1.5%、 Zn:0.3〜1%、 を含有し、残りがAlと不可避不純物からなる組成(以
上重量%)を有することを特徴とする耐孔食性にすぐれ
たA1合金。
[Claims] A composition containing lsi: 0.2 to 1.2%, Mg: 0.45 to 1.5%, Zn: 0.3 to 1%, with the remainder consisting of Al and inevitable impurities. An A1 alloy with excellent pitting corrosion resistance, characterized by having (the above weight %).
JP53079806A 1978-07-03 1978-07-03 Al alloy with excellent pitting corrosion resistance Expired JPS595661B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP53079806A JPS595661B2 (en) 1978-07-03 1978-07-03 Al alloy with excellent pitting corrosion resistance

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP53079806A JPS595661B2 (en) 1978-07-03 1978-07-03 Al alloy with excellent pitting corrosion resistance

Publications (2)

Publication Number Publication Date
JPS558426A JPS558426A (en) 1980-01-22
JPS595661B2 true JPS595661B2 (en) 1984-02-06

Family

ID=13700452

Family Applications (1)

Application Number Title Priority Date Filing Date
JP53079806A Expired JPS595661B2 (en) 1978-07-03 1978-07-03 Al alloy with excellent pitting corrosion resistance

Country Status (1)

Country Link
JP (1) JPS595661B2 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996035819A1 (en) * 1995-05-11 1996-11-14 Kaiser Aluminum And Chemical Corporation Improved damage tolerant aluminum 6xxx alloy

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS49118064A (en) * 1973-03-14 1974-11-12

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS49118064A (en) * 1973-03-14 1974-11-12

Also Published As

Publication number Publication date
JPS558426A (en) 1980-01-22

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