JPH07228938A - Aluminum alloy for galvanic anode - Google Patents

Abstract

PURPOSE:To produce an aluminum alloy for galvanic anode, suitable for use in corrosion protection for reinforcing bars in a reinforced concrete structure. CONSTITUTION:The aluminum alloy, useful for corrosion protection of reinforcing bars and having a composition consisting of, by weight, 10-50% Zn, 0.03-0.6% In, 0.0005-0.05% Zr, 0.05-0.3% Si, 0.02-0.2% Ce or 0.005-0.1% Ti, 0.001-0.02% B, and the balance Al with inevitable impurities, is prepared.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for galvanic anodes suitable for corrosion protection of reinforcing bars in reinforced concrete structures.

[0002]

2. Description of the Related Art Corrosion of reinforcing bars in a reinforced concrete structure does not usually progress because the concrete is a strong alkali. However, when the above-mentioned structure is provided in, for example, seawater or seawater, or chloride is sprayed to prevent freezing, and the structure is placed in an environment where salt water penetrates, the progress of corrosion becomes a problem.

In order to solve this problem, zinc alloys have been conventionally studied in the galvanic anode method, which is inexpensive and stable in corrosion protection for a long time. This zinc alloy is one of the important characteristics of galvanic anodes. There is a problem that a certain anode potential is too high.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems and to provide a flow suitable for the corrosion protection of the reinforcing bars in the reinforced concrete structure, that is, the anode potential is sufficiently base and the generated electricity is sufficiently large. An object is to provide an aluminum alloy for an electrolytic anode.

[0005]

According to the present invention, the first object is to achieve 10 to 50% by weight of Z.
n, 0.03 to 0.6% by weight of In, 0.0005 to
An aluminum alloy for galvanic anodes containing 0.05% by weight of Zr and the balance of Al and unavoidable impurities. The second one is 10 to 50% by weight of Zn, 0.03.
~ 0.6 wt% In, 0.05-0.3 wt% Si
Is an aluminum alloy for galvanic anodes containing Al and unavoidable impurities. Then the third one is 1
0 to 50% by weight Zn, 0.03 to 0.6% by weight I
n, 0.02-0.2 wt% Ce, balance Al
And an aluminum alloy for galvanic anodes, which comprises unavoidable impurities. Further, the fourth one is 10 to 50% by weight of Z.
n, 0.03 to 0.6 wt% In, 0.005 to 0.
This is an aluminum alloy for galvanic anodes containing 1% by weight of Ti, 0.001 to 0.02% by weight of B, and the balance of Al and unavoidable impurities.

[0006]

In the aluminum alloy of the present invention, Zn and In both have the effect of increasing the amount of electricity generated by suppressing the self-dissolution of the alloy, and Zn is less than 10% by weight or In is 0.03%. If it is less than wt%, the action is not sufficiently exhibited. On the other hand, when Zn exceeds 50% by weight or In exceeds 0.6% by weight, the anode potential tends to become noble.

In the aluminum alloy of the first invention,
Zr has the same action as Zn and In described above, and if Zr is less than 0.0005% by weight, the action is not sufficiently exhibited. On the other hand, if Zr exceeds 0.05% by weight, coarse distribution will occur at the crystal grain boundaries of the alloy and the amount of electricity generated will decrease. Further, in the aluminum alloy of the second invention, S
i has the same action as Zn and In described above, and when Si is less than 0.05% by weight, the action is not sufficiently exhibited,
If it exceeds 0.3% by weight, the anode potential tends to be noble. Next, in the aluminum alloy of the third aspect of the present invention, Ce has an effect of increasing the amount of electricity generated by preventing pitting corrosion of the alloy, and if Ce is less than 0.02% by weight, the effect is not sufficiently exhibited. On the other hand, when Ce exceeds 0.2% by weight, the anode potential tends to become noble. Further, in the aluminum alloy of the fourth aspect of the present invention, Ti and B make the crystal structure of the alloy a fine granular crystal instead of a coarse columnar crystal to prevent pitting corrosion and groove corrosion (corrosion on both sides remaining in groove shape). This has the effect of increasing the amount of electricity generated, and if Ti is less than 0.005% by weight or B is less than 0.001% by weight, this effect is not fully exhibited. On the other hand, when the amount of Ti exceeds 0.1% by weight or the amount of B exceeds 0.02% by weight, the generated electricity amount decreases.

[0008]

【Example】

Examples 1 to 11 and Comparative Examples 1 to 10 21 kinds of aluminum alloys were melted in the atmosphere and then die-cast to obtain round bar-shaped ingots having a diameter of 25 mm and a length of 250 mm. Then, a performance test of the galvanic anode was performed using these ingots as samples. The test was carried out by the "Corrosion and Anticorrosion Association""galvanic anode test method"("galvanic anode test method and description", anticorrosion technology, Vol. 31, p612-62).
0,1982).

The test method is outlined as follows.
That is, these samples had a surface of sandpaper of 240
The surface was ground to a roughness of 20 mm, and the side surface was left with 20 cm ² and the others were covered with vinyl tape for insulation. Next, KCl
32.0 g / l, NaOH 24.5 / l, KOH1
An aqueous solution having a composition of 0.0 g / l and Ca (OH) ₂ 0.1 g / l was filled in a 1 liter beaker as a concrete simulated test solution. The sample is the anode in the center of the beaker,
A stainless steel cylindrical plate was arranged as a cathode along the side wall of the beaker (distance between electrodes: 30 mm). Then, a direct current stabilized power supply was sandwiched between the anode and the cathode for connection. The energization was performed for 240 hours under the constant current condition of the anode current density of 0.1 mA / cm ² . The amount of electricity generated was calculated from the weight reduction of the sample, and the anode potential was measured by using the silver-silver chloride electrode as a reference electrode for the anode potential immediately before the end of energization. Table 1 shows the composition of the tested anode sample and the obtained results.

[0010]

[Table 1]

Examples 12 to 44, Comparative Examples 11 to 40 Performance tests of galvanic anodes were carried out in the same manner as in Example 1 after 63 types of aluminum alloys were melted in the air by changing the composition and die casting. Was done. The compositions of the tested anode samples and the obtained results are shown in Tables 2, 3 and 4.

[0012]

[Table 2]

[0013]

[Table 3]

[0014]

[Table 4]

[0015]

As described above, the aluminum alloy of the present invention has a sufficiently large generated electricity amount of 1500 A · hr / kg or more and an anode potential of −1000 mV or less, which is sufficiently base, and prevents the reinforcement of reinforcing steel in a reinforced concrete structure. It turns out to be suitable for food.

Claims (4)

[Claims] 1. 10 to 50% by weight of Zn, 0.03 to
An aluminum alloy for galvanic anodes containing 0.6% by weight of In and 0.0005 to 0.05% by weight of Zr, with the balance being Al and inevitable impurities. 2. Zn of 10 to 50% by weight, 0.03 to
An aluminum alloy for galvanic anodes containing 0.6% by weight of In, 0.05 to 0.3% by weight of Si, and the balance being Al and unavoidable impurities. 3. 10 to 50% by weight of Zn, 0.03 to
An aluminum alloy for galvanic anodes, containing 0.6% by weight of In and 0.02 to 0.2% by weight of Ce, and the balance being Al and inevitable impurities. 4. 10 to 50% by weight of Zn, 0.03 to
0.6 wt% In, 0.005-0.1 wt% T
i, 0.001 to 0.02% by weight of B, the balance being A
Aluminum alloy for galvanic anode consisting of 1 and unavoidable impurities.