JPH11310840A - Aluminum alloy for galvanic electricity anode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an alloy for galbvanic electricity anode having a sufficiently basic anode potential and a sufficiently large generating quantity of electricity under a corrosive circumstance by making a specific amount of Zn and Ge contained in an aluminum alloy. SOLUTION: An alloy for galvanic electricity anode is composed of, by weight, 7-50% Zn, 0.01-0.6% Ge, and the balance Al with inevitable impurities. Zn and Ge have an effect of maintaining an anode potential sufficiently basic as well as maintaining a generated amount of electricity sufficiently large by suppressing self-dissolving of the alloy. In order to obtain the most basic anode potential, Zn content is made to be 7-20 weight %, and in order to get the largest generating quantity of electricity, Zn content is made to be 30-50%. In order to obtain an excellent generating quantity of electricity and anode potential well balanced, Zn content is made to be 10-40%. This aluminum alloy for galvanic electricity anode has a generating quantity of electricity sufficiently large as much as >=1,250 A.hr/kg and an anode potential sufficiently basic as low as <=-1,300 mV, so that is suitable for anticorrosion of reinforcing bar in a concrete structure.

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 a galvanic anode suitable for preventing corrosion of reinforcing steel in a reinforced concrete structure.

[0002]

2. Description of the Related Art Reinforcing bars in a reinforced concrete structure do not corrode much in an ordinary environment because concrete is strongly alkaline. However, if the above-mentioned structure is placed in an environment where salt water penetrates, for example, by being provided on seawater or seawater, or by spraying chlorides for preventing freezing, corrosion progresses and becomes a problem.

[0003] In order to solve this problem, a galvanic anode method, which has the potential to provide stable corrosion prevention at low cost for a long time, has attracted attention. Then, a galvanic anode method using a zinc alloy for the galvanic anode has been studied.

The galvanic anode method is a method in which a current generated by corrosion of a galvanic anode having a low anode potential is obtained as an anticorrosion current. Volume and anodic potential. here,
The amount of generated electricity is the amount of anticorrosive electricity per unit weight, and the anodic potential is the natural potential of the galvanic anode. The greater the value of the amount of generated electricity and the lower the anode potential, the better the galvanic anode.

However, zinc alloys have a high anodic potential (noble).
There is a problem that too.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an aluminum alloy for a galvanic anode having a sufficiently low anode potential and a sufficiently large amount of generated electricity in a reinforced corrosion environment called reinforced concrete. It is in.

[0007]

SUMMARY OF THE INVENTION The present invention achieves the above objects by providing 7 to 50% by weight of Zn and 0.1 to 0.5% by weight of Zn.
This is an aluminum alloy for a galvanic anode containing 01 to 0.6% by weight of Ge and the balance of Al and inevitable impurities.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the aluminum alloy for a galvanic anode according to the present invention, both Zn and Ge maintain a sufficiently large amount of generated electricity by suppressing the self-melting of the alloy, and sufficiently reduce the anode potential. There is an action to maintain.

As the content of Zn increases, the amount of generated electricity increases and the anode potential shifts from the base side to the noble side. Therefore, by selecting the Zn content as follows, for example, the aluminum alloy for a galvanic anode of the present invention having a desired amount of generated electricity and an anode potential can be used. That is, (1) an aluminum alloy for a galvanic anode having a Zn content of 7 to 20% by weight to obtain the lowest anode potential; and (2) a Zn content of 30 to obtain the largest generated electricity. Select an aluminum alloy for a galvanic anode of up to 50% by weight, and (3) an aluminum alloy for a galvanic anode having a Zn content of 10 to 40% by weight in order to obtain a good balance between the amount of generated electricity and the anode potential. Can be used.

When Zn is less than 7% by weight or Ge is 0.0
If the amount is less than 1% by weight, the above effect is not sufficiently exhibited, and the amount of generated electricity decreases. Further, when Zn exceeds 50% by weight or G
When e exceeds 0.6% by weight, the anode potential tends to be noble.

[0011]

EXAMPLES [Examples 1 to 11, Comparative Examples 1 to 10] Twenty-one types of aluminum alloys were melted in the air and then cast in a mold to obtain round bar-shaped ingots having a diameter of 25 mm and a length of 250 mm.
Table 1 shows the composition of the ingot.

Thereafter, a performance test of the galvanic anode was performed using these ingots as samples. The test was conducted using the galvanic anode test method established by the Corrosion and Corrosion Protection Association of Japan (“Glectroelectric anode test method and its commentary”, anticorrosion technology, Vol. 31, p 612-620,
1982).

The above test method is briefly described as follows.
That is, the surface of the sample was polished until the roughness of the sandpaper became 240, leaving 20 cm ^{2 of} the side surface,
The other surface was insulated with vinyl tape. Then K
Cl: 32.0 g / l, NaOH: 24.5 g / l, K
OH: 10.0 g / l, Ca (OH) ₂ : 0.1 g / l
An aqueous solution having the following composition was filled in a 1-liter beaker as a concrete simulation test liquid. Further, the sample was disposed as an anode in the center of the beaker, and a stainless steel cylindrical plate was disposed as a cathode along the side wall of the beaker (distance between the electrodes: 30 m).
m). Then, a connection was made with a DC stabilized power supply interposed between the anode and the cathode. Energization is performed at an anode current density of 1.0 mA / c.
The test was performed for 240 hours under a constant current condition of m ² . The amount of generated electricity is
It was calculated from the weight loss of the sample before and after the start of energization. The anodic potential was measured immediately after the end of energization using a silver-silver chloride electrode as a reference electrode.

Table 1 shows the obtained results.

[0015]

[Table 1]

[0016]

As described above, the aluminum alloy for a galvanic anode according to the present invention has a generated electric quantity of 1250 A · hr / k.
g or more, and the anode potential is -1300 mV or less, which is sufficiently low, and it is understood that it is suitable for corrosion prevention of reinforcing steel in a reinforced concrete structure.

Further, it can be seen that the composition and the composition corresponding to the corroding corrosive environment to be used can be selected and used because of excellent correlation between the amount of generated electricity and the anode potential and the composition.

Claims (4)

[Claims] 1. A method according to claim 1, wherein said Zn is present in an amount of 7 to 50% by weight.
An aluminum alloy for a galvanic anode containing about 0.6% by weight of Ge and the balance being Al and inevitable impurities. 2. The aluminum alloy for a galvanic anode according to claim 1, wherein the Zn content is 7 to 20% by weight. 3. The aluminum alloy for a galvanic anode according to claim 1, wherein the Zn content is 10 to 40% by weight. 4. The aluminum alloy for a galvanic anode according to claim 1, wherein the Zn content is 30 to 50% by weight.