JPS5887246A - Composite al alloy material for water tank with superior pitting corrosion resistance - Google Patents

Abstract

PURPOSE:To enhance the corrosion resistance and pitting corrosion resistance of the resulting composite Al alloy material by using an Al alloy having a specified composition contg. Mg and Cr or Mn as a core material and an Al alloy having a specified composition contg. Mg and Zn as a shell material. CONSTITUTION:An Al alloy consisting of, by weight, 2.0-5.6% Mg, 0.05-0.35% Cr and/or 0.05-1.0% Mn and the balance essentially Al is used as a core material, and an Al alloy consisting of 0.3-5.6% Mg, 0.1-1.0% Zn and the balance essentially Al or further contg. 0.05-0.35% Cr and/or 0.05-1.0% Mn is used as a shell material. One side or both sides of the core material is clad with the shell material to obtain a composite material with superior corrosion resistance, especially pitting corrosion resistance. When a water tank is manufactured with the composite material, it can be used over a long term.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an M alloy composite material which has excellent pitting corrosion resistance and is particularly suitable for use in the manufacture of swimming pools, reservoirs, water storage tanks and the like.

Conventional-1 Generally, JI is used to manufacture the various water storage containers mentioned above.
d-Mg alloys such as S 5052 and 5083,
That is, it contains Mg: 2.2 to 4.9%, and further contains cr
M-Mg containing one or two of: -0.05 to 0.35% and Mn: 1.0% or less, with the remainder consisting of AQ and unavoidable impurities (weight %)
Single plate materials made of these alloys are used because they have relatively good corrosion resistance, excellent formability, and medium or higher strength. The fact that the M-Mg alloy exhibits relatively good corrosion resistance is due to the formation of a strong natural oxide film unique to this alloy on its surface. However, in the above-mentioned water storage containers manufactured from veneer materials of AQ-Mg alloy, impurities are unavoidably contained in the oxide film formed on the surface, and thermal or mechanical scratches occur. When this happens, this part cannot exhibit sufficient corrosion resistance and begins to dissolve selectively, which often results in significant local corrosion, that is, pitting corrosion. -That's it.

Therefore, from the above-mentioned viewpoint, the present inventors aimed to obtain a material for water storage containers that does not cause pitting corrosion, and in particular, to obtain a material for water storage containers that does not cause pitting corrosion. As a result of research focusing on
G-based alloy is used as the core material, Mg: 0.3 to 5.6%, Zn
: Contains 0.1 to 1.0%, and further contains c as necessary.
r: 0.05~0.35% and Mn: 0.05~
One or both sides of the core material is clad with an M alloy containing one or two of 1.0% and having a composition (or more by weight) consisting of M and unavoidable impurities as a skin material. When made into a composite material, this composite material has good moldability and medium or higher strength due to the core material, while the skin material has a natural oxide film on the surface due to the coexistence of Mg and Zn. Zn is formed, so it has corrosion resistance, and even if the skin material contains unavoidable impurities or is scratched thermally or mechanically, Zn
As a result of the action of the coating, pitting corrosion does not occur because it becomes a horizontally spreading type of general corrosion.In addition, under harsh environments containing a large amount of Cu ions, pitting corrosion may occur in the skin material. In some cases, the skin material is electrochemically less noble than the core material due to its Zn content, so the sacrificial anode effect of the skin material effectively protects the core material from corrosion and prevents pitting corrosion. It was discovered that this does not extend to the core material, and therefore, when used in the manufacture of water storage containers, it can be used for a long period of time.

This invention was made based on the above knowledge, and the core material contains Mg: 2. Contains O ~ 5.6%, further Cr: 0.05 ~ 0.35% and Mn: 0.05
Contains one or two of ~1.0%, with the remainder being M
It is composed of A1 alloy having a composition consisting of
: Contains 0.1 to 1.0%, and further contains cr as necessary.
:0.05~0.35% and Mn:0.05~1.0
An M alloy composite material for water storage containers with excellent pitting corrosion resistance, which is made of an M alloy containing one or two of the following: 1 or 2, with the remainder consisting of M and unavoidable impurities (weight %). It has characteristics.

Next, in the A1 alloy composite material of the present invention, the reason why the component compositions of the core material and the skin material are limited to the above-mentioned standard will be explained.

(a) Core material■ Mg The Mg component has the effect of improving the strength of the core material, but if its content is less than 2.0 inches, it is not possible to secure a strength of medium or higher; If the content exceeds %,
Since forming processability such as hot rolling deteriorates, the content is determined to be 2.0 to 5.6 inches.

■Cr and Mn These components have the effect of refining crystal grains and improving the strength of the core material, but their content is Cr:0.
0.05% and Mn: less than 0.05%, the desired strength cannot be ensured, while Cr: 0.05% and Mn: less than 0.05%, respectively.
If the content exceeds Cr: 35% and Mn: 1.0%, giant crystallized substances are likely to be formed during casting, leading to property deterioration, so the respective contents are reduced to Cr: 0.
105 to 0.35%, MH: o, o5 to 1.0%.

(b) Skin material■ Zn Zn component, when coexisting with Mg, forms a natural oxide film on the surface of the skin material to improve corrosion resistance, and prevents pitting corrosion by spreading the dissolution laterally and causing full corrosion. Furthermore, even if pitting corrosion occurs in the skin material under harsh environments, the sacrificial anode effect brought about by the Zn content prevents pitting corrosion from reaching the core material. If the content is less than 0.1%, the desired effect cannot be obtained; on the other hand, if the content exceeds 1.0%, uneven corrosion and pitting corrosion will occur in the stone. As the amount of corrosion increases and the sacrificial anode effect on the core material of the skin material disappears relatively quickly, its content is reduced to 0.
．． It was set as 1 to 1.0ch.

■ Mg As mentioned above, the Mg component forms a strong natural oxide film in coexistence with Zn, gives excellent corrosion resistance to the coating material, and has the effect of solid solution strengthening. is less than 0.3%, the desired effect cannot be obtained in the above action,
On the other hand, if the content exceeds 5.6%, not only will workability in hot rolling etc. deteriorate, but depending on the heat treatment conditions, An-Mg-based precipitates may be formed at grain boundaries. As a result, uneven island corrosion and pitting corrosion including intergranular corrosion will occur, so the content should be reduced to 0.3~
It was set at 5.6%.

■ Cr and Mn These components have the effect of refining crystal grains and improving strength, as well as reinforcing the general corrosion type and significantly suppressing the occurrence of uneven corrosion and pitting corrosion. Cr: o, o 5 is included as necessary when used under harsh conditions that require these properties, respectively.
% and MH: less than 0.05%, the desired effect of improving the above action cannot be obtained, while Cr: 0.
．． When containing more than 35% and Mn: 1.0%,
Giant tools are more likely to form during casting, leading to uneven corrosion, and corrosion progresses faster.
The content is Cr: 0.05 to 0.35, respectively.
%, Mn: 0.05 to 1.0%.

Next, the M alloy composite material of the present invention will be specifically explained with reference to Examples.

Examples M alloys 1 to 6 for skin materials of the present invention having the final component compositions shown in Table 1 were prepared by the usual melting and casting method. Comparative leather material A1
Alloys 1-4. and At alloy 1.2 for core materials of the present invention were manufactured, respectively. In addition, comparative A2 alloys 1 to 4 for skin materials have compositions in which the content of at least one of the constituent components (shown with an asterisk in Table 1) is outside the scope of this invention. It is something. In addition, all A8 alloys contain Fe: 0.21 to 0.22% and Si: as inevitable impurities.
It contained 0.08-0.09%.

Next, the above-mentioned M alloys 1 to 6 for skin materials of the present invention. Comparative leather material A
A alloy 1-4. and M Alloy 1.2 for the core material of the present invention were homogenized under normal conditions, and then hot rolled under the same normal conditions to form the AI for skin material of the present invention! Alloy 1~
6 and comparative M alloys 1 to 4 for skin materials are plates [I: 1 mm
The hot-rolled plate of - At alloy 1.2 for strength wood core material has a plate thickness:
BII+71! These hot-rolled sheets were stacked together in the combinations shown in Table 2 and cold-rolled to a thickness of:
Inventive M alloy composites 1 to 6 and comparative A1 alloy composites 1 to 5 each having double-sided cladding were manufactured by preparing the following materials.

In addition, for the purpose of comparison, the hot-rolled At alloy 1 for core material of the present invention is
1 A comparative M alloy veneer material having a thickness of 1 mm was produced by cold rolling the top plate.

Next, the M alloy composites 1 to 6 of the present invention obtained as a result.
Comparative M alloy composites 1 to 5. And comparative AQ alloy veneer materials were subjected to a tap water immersion test in which they were immersed in tap water at 40°C containing 1 ppm of Cu ions for 60 days, and samples containing 100 ppm of CT- ions, SO- ions, and HCO2- ions, respectively. , and further added 1 ppp of Cu ions.
An aqueous solution immersion test was conducted for 60 days in an aqueous solution containing m at 40°C, and after the test, corrosion products were removed to reduce the corrosion weight.
The number of pitting corrosion and the maximum pitting depth were measured. The measurement results are also shown in Table 2.

As shown in Table 2, the M alloy composite materials 1 to 6 of the present invention were superior to the comparative AA alloy composite materials 1 to 6 in any of the immersion tests.
Excellent corrosion resistance compared to 5 and comparative M alloy veneer materials,
and pitting corrosion resistance, and it is clear that the pitting corrosion resistance in particular is extremely excellent.

As mentioned above, the M alloy composite material of the present invention has excellent corrosion resistance and pitting corrosion resistance, and the core material ensures excellent formability and medium or higher strength.
It is particularly suitable for use in the manufacture of water storage containers, and in practical use, pitting corrosion does not extend to the core material even under severe usage conditions such as exposure to aqueous solutions containing large amounts of CU ions. As a result, it has industrially useful properties such as being able to be used for an extremely long period of time.

Applicant: Mitsubishi Aluminum Corporation Agent Tomi 1) Kazuo

Claims (2)

[Claims] (1) The core material contains Mg: 2.0 to 5.6%, and further contains cr: o, o 5 to O, '35% and Mn:
The skin material is composed of an M alloy containing one or two of Mg: 0.05 to 1.0, with the remainder consisting of M and inevitable impurities, and the skin material has Mg: 0.3 to 5. .6%
,, A water storage with excellent pitting corrosion resistance characterized by being composed of an M alloy having a composition (weight %) containing 0.1 to 1.0% of Zn and the remainder consisting of M and unavoidable impurities. A1 alloy composite material for containers. (2) The core material contains Mg: 2.0 to 5.6%, and further contains Cr: 0.05 to 0.35% and Mn: o, o
The skin material is made of an M alloy containing one or two of Mg: 0.3-5. Contains 0.1 to 1.0% of 6chi, Kozukeji, and further Cr: 0.05
~0.35% and Mn: o, o 5 to 1.0%.Contains one or two of the following, and the remainder is M and unavoidable impurities (weight%). Ag for water storage containers with excellent pitting corrosion resistance
. Alloy composite.