JPS59193283A - Device for corrosion prevention using galvanic anode - Google Patents

Abstract

PURPOSE:To obtain a galvanic anode corrosion preventing device for electrically preventing the corrosion of a steel or metallic structure existent in soil or an electrolyte using an Al alloy which has been difficult to use in soil so far, by conjointly using a solar cell. CONSTITUTION:When a solar cell 7 accepts sunlight, electric power generated by the solar cell 7 flows through a sacrified anode 2 into the surface layer of an object to be corrosion prevented existent in soil 3, to heighten the effect of electric corrosion prevention. Hereon, the lump sum of the electromotive forces of the cell 7 and the anode 2 wholly act as effective voltage for applying an electric current without the need of decomposition voltage on the surface of the electrode. In case without sunshine, an electric current corresponding to the electromotive force of the anode 2 itself is applied. Said electric current is smaller than that during sunshine, but the reduction of the corrosion preventive effect is not too large because of the residual corrosion preventive effect which has been heightened during the sunshine. In addition, in the case without sunshine, an electric current generated by the electrode 2 flows through a relay 3 or a diode 9 connected in parallel with the cell 7. Hence, the conjoint use of a battery which has been considered as indispensable heretofore in using a solar cell is not necessary.

Description

[Detailed description of the invention] The present invention relates to the provision of a novel galvanic anodic protection device.

Cathodic protection methods for metals in electrolytes, mainly steel structures, are broadly divided into galvanic anode methods and external power supply methods. Each has advantages and disadvantages, and is used depending on the environment and conditions.

In other words, Figure 1 is an explanatory diagram of the galvanic anode method.

As shown in the figure, a galvanic anode 2, which is also buried in the soil 3, is electrically connected to a corrosion protection target 1 in the soil 3.
Three types of alloys, magnesium, zinc, and aluminum, are widely used as the galvanic anode 2, and their approximate characteristic potentials (based on copper sulfate electrodes) are -1 and 1, respectively.
6V, -1,OV.

-1.IV, a current is generated due to the difference between this and the potential 9 of the object, for example, -0.5V in the case of steel, and this becomes a corrosion protection current.

The potential of these alloys is unique based on their composition, and its value can hardly be changed artificially. For example, in soils with high electrical resistivity, only magnesium anodes with the highest potential can be used, and in this case it may be necessary to adjust the number and size of anodes depending on the conditions. In addition, with the current magnesium anode, only about 50% of the inherent theoretical amount of electricity generated is utilized as an effective amount of electricity.

This efficiency becomes worse as the current density on the anode surface becomes smaller.

In addition, Fig. 2 is an explanatory diagram of the external power supply system, and in Fig. 2, 6 is a durable electrode, 4 is a DC power supply device interposed between the corrosion protection object 1 and the durable electrode 6, and 5 is an AC input. Show each.

This external power supply method has the advantage that the current can be adjusted by arbitrarily changing the output voltage of the DC power supply device 4, but it always consumes power from the power supply.

Relatively frequent management is also required.

Furthermore, if the AC power source is remote, the wiring costs will be large. In addition, the commonly used durable electrode 6 (graphite high silicon iron, magnetic iron oxide, etc.) requires a voltage of about 3 cm or more to exceed the decomposition voltage.

In view of the above-mentioned circumstances, the present invention has been developed to eliminate the drawbacks of the two conventional construction examples and to be able to supply an effective anti-corrosion current at all times. The purpose of this invention is to use an aluminum alloy anode, which has conventionally been difficult to use in soil, to provide electrolytic protection for steel or metal structures in soil or electrolyte.

Hereinafter, this will be explained in detail based on embodiment figures.

That is, as shown in FIG. 3, the corrosion protection object 1 in the soil 3
A galvanic anode 2 is buried near the. The galvanic anode 2 may be made of magnesium alloy, zinc alloy, or aluminum alloy, but aluminum is preferable. The reason for this is that aluminum-based anodes have the highest current efficiency, or in other words, the amount of consumption due to outflow current is the least among the three types of anodes. For reference, the amount of consumption per ampere/year is 8.0 kg/A of magnesium.
y, zinc 11.2 kg/A)', aluminum 3.5 kg/
It becomes Ay.

When these galvanic anodes 2 are installed, it is preferable to fill the area around the anode with a bank fill material made of a mixture of bentonite gypsum, mirabilite, etc., in order to uniformly wear out the anode and reduce ground resistance.

Next, connect the lead wire from this galvanic anode 2 to the corrosion protection target 1.
Connect to some part of. Insert and connect the solar self in series to that circuit. At this time, the + side terminal of the solar self is placed on the galvanic anode 2 side, and the - side terminal is used as an example of an object. The location and direction of solar self-installation should be selected where the sunlight hours are the longest. The output characteristics of the solar self are selected taking into consideration the object to be protected against corrosion, the environment, etc. Furthermore, a contact relay 8 is connected in parallel with the solar self.

This relay 8 has the ability to open when the solar self operates and close when the solar self does not operate. Alternatively, instead of the contact relay 8, a diode 9 having as low an internal resistance as possible may be connected in the positive direction.

In the apparatus shown in FIG. 3, when the solar self receives sunlight, the electric power generated by the solar self flows into the surface of the object 1 to be protected from corrosion through the galvanic anode 2, thereby increasing the electrolytic protection effect. No decomposition voltage is required at the electrode surface, and the sum of the electromotive forces of both the solar self and the current anode 2 acts as an effective voltage for current flow.

Next, when there is no sunlight, a current flows according to the electromotive force of the galvanic anode 2 itself, and although this current is lower than when there is sunlight, there is also a residual effect of the anticorrosion effect that was mentioned during sunlight, so the decrease in the anticorrosion effect is not that much. It's not big.

In the absence of sunlight, the current generated from the galvanic anode 2 flows through the relay 8 or diode 9 connected in parallel to the solar self. 5 Conventional.

There is no need to use batteries together, which was considered essential when using solar cells.

As is clear from the above explanation, 1. According to the present invention, a galvanic anode, which was conventionally difficult to use in soil or a high resistivity environment, can be used with high current efficiency, and an AC power source is not required, which is very economically advantageous. Yes.

Galvanic anode method alone is not effective enough for steel structures buried in the soil 1 For example, corrosion protection of gas station tanks, gas and water pipes, steel towers in areas where AC power is difficult to obtain, such as mountainous areas and deserts. It is extremely suitable for use in corrosion protection for legs, piping, etc.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams of conventional cathodic protection methods;
FIG. 3 is an explanatory diagram of the anticorrosion device of the present invention. 1... Corrosion protection target, 2... Galvanic anode, 3... Soil, 7... Solar cell, 8... Relay, 9... Diode's 2γ layer gear "zk's -4" Ding・455-

Claims (1)

[Claims] ω In a corrosion protection device using a two current current @ electrode method for a metal structure in soil or an electrolyte, a solar cell is connected in series between the metal structure and a current current anode, and the current current anode A galvanic anode corrosion protection device combined with a solar cell that constitutes a corrosion protection circuit in which the generated current and the output current of the solar cell are superimposed to improve the corrosion protection effect. (2) In a galvanic anode corrosion protection device for metal structures in soil or electrolyte, a solar cell is connected in series between the metal structure and the galvanic anode, and the current generated by the galvanic anode is An anti-corrosion circuit is constructed in which the output current of the battery is superimposed to improve the anti-corrosion effect, and a backflow prevention relay or diode is connected in parallel with the solar cell to the same anti-corrosion circuit to prevent current from flowing when the solar cell is not operating. A galvanic anode corrosion protection device combined with solar cells that maintains the corrosion protection effect only by the current generated by the anode.