JPH06340986A - Exhaustible anode for corrosive protection of marine structure and preparation thereof - Google Patents

Abstract

(57) [Summary] [Objective] In a consumable anode for protection of corrosion resistance of marine structures, to improve the protection state of the surface of structures while keeping the geometric size and weight small. An anode carrier device (1) is provided with an outer coating with an anode material (2) having a greater negative electrochemical potential than the material making up the marine structure to be protected, the coated carrier device being provided with an anode material (2). An outer coating is provided with another anode material 3 having a negative electrochemical potential even greater than that.

Description

Detailed Description of the Invention

The present invention relates to a new consumable anode for the protection of the corrosion resistance of marine structures, which anode comprises
Its special multi-layered morphology makes it possible to reduce the amount of anode material required, which, in addition to the self-evident economic benefits, also improves the surface protection of offshore structures, providing tighter protection. A large amount of deposit will be formed.

The invention also relates to a method of making such a consumable anode.

According to the prior art, the corrosion resistance protection of marine structures with consumable anodes is now one of the most used techniques in the field, the development of which leads to efficiency, weight and cost savings. As a result, it has become possible to find aluminum alloys, zinc alloys and magnesium alloys as optimum anode materials.

According to such a technique, a consumable anode made of an anode material having a greater negative electrochemical potential than the material of which the marine structure to be protected is made develops a bias that establishes a protection current. This protective current, in turn, causes protective calcareous deposits to form on the structure.

The higher the bias, the greater the negative electrochemical potential of the anode material used.

On the other hand, the above-mentioned protective current required for the sufficient protection of the marine structure is not only limited to the marine conditions such as temperature, salinity and oxygen content but also the surface condition of the marine structure to be protected. That is, depending on whether or not calcareous deposits are present. Therefore, from the above, in the early stages of the life of protected marine structures, protective calcareous deposits are not yet fully formed and must have a maximum protective current, which need Depending on the quality of the calcareous deposits formed in the early stages, this may result in a decrease in later stages of the structure's life.

As can be seen from the above, the essential elements in the design of a consumable anode are the ability of the anode to supply the large required starting current in the early stages of the marine structure, as well as the marine structure. The ability to maintain the protection of the structure over the subsequent stages of its useful operating life. However, since the starting current that a consumable anode can deliver depends not only on the ocean conditions and its electrochemical potential, but also on its surface or shape, said conditions are in fact the geometry of the consumable anode. The dimensions and weight must be determined according to the starting current required of the offshore structure to be protected and the protection current to be generated in the subsequent working stages of this structure after the formation of the protective calcareous deposit. It brings results.

By the way, since magnesium and its alloys show the largest negative electrochemical potentials, consumable anodes made of magnesium alloys generate a large bias and a large initial anodic current, which results in a tightly packed calcareous substance. The formation of deposits can provide a very effective protection of offshore structures, which will reduce the strength of the protection current required at subsequent stages of their useful operating life. , Can be considered to be the optimal solution for protection of the corrosion resistance of this offshore structure. However, in practice, such magnesium alloy anodes, due to their low anode efficiency, unless used in unacceptably large amounts due to their large weight and high cost,
It cannot cover the entire useful operating life of the marine structure being protected.

In fact, the most widely used consumable anodes for the protection of offshore structures today are aluminum alloys which, even when used in small amounts, ensure complete protection of the protected structure over its entire life. Or a zinc alloy, the requirement for high initial current is met by appropriately increasing the geometrical dimensions of the anode.

The object of the present invention is to eliminate the abovementioned disadvantages, and therefore to protect its geometrical dimensions while keeping its corrosion resistance protection and weight low over the operating life of the structure. To provide a consumable anode for the protection of corrosion resistance of offshore structures, capable of supplying the high starting currents initially required to produce an effective protective layer of calcareous deposits on offshore structures. It is in.

[0011] The above objective is to make anode materials, generally zinc alloy or aluminum alloy, which constitute the outer coating adhered to the carrier supporting the anode, to have a greater negative electrical conductivity than the zinc alloy or aluminum alloy based anode materials. This is accomplished by using a multi-layer consumable anode which is externally coated with another anode material, typically made of a magnesium alloy, which has a chemical potential.

The advantage exhibited by such a multi-layer consumable anode over the conventional anode known from the prior art derives substantially from the action of the initial bias and the anode efficiency, the consumable anode being 2 It is composed of two different anode materials and benefits the most from their natural properties.

In fact, the magnesium alloy thus constituting the outermost coating with a small anode capacity and a large negative electrochemical potential acts at the first stage of the useful working life of the marine structure to be protected. However, the inner anode material made of aluminum alloy or zinc alloy, which starts to work only after all of the outermost magnesium coating has been consumed, is already biased and allows to reduce the geometrical dimensions of the anode. The inner side, which is coated with a dense calcareous deposit, acts on surfaces requiring a small protection current value and protects this structure for the remainder of the useful working life of the structure. The result is a reduction in the weight of the anode material.

In experiments, the use of a multi-layer consumable anode according to the invention makes it possible to obtain a considerable economic savings of 20% compared to the use of conventional consumable anodes known from the prior art. It was proved that.

In summary, the present invention comprises a carrier device provided with an outer coating made of an anode material having a greater negative electrochemical potential than the material making up the protected marine structure. A consumable anode for corrosion resistance protection is characterized in that the anode is provided with an outer coating made of another anode material having a greater negative electrochemical potential than the anode material.

And, according to a preferred feature of the present invention,
A method of making a consumable anode for corrosion protection of marine structures comprises casting the anode material, which constitutes the outer coating of a carrier device of the anode, into an ingot mold or chill or mold,
The other anode material is cast into another ingot mold or chill or mold around the anode formed in the previous step.

The present invention will now be described in detail with reference to the accompanying drawings showing preferred embodiments as non-limiting examples, but without departing from the scope of the present invention, technical or It can be structurally modified. Thus, for example, without relying on the continuous process of casting two anode materials for sandwich-coating the anode carrier device in an ingot mold or a chill or mold, the anode material with a small negative electrochemical potential is already By coating the carrier device being coated with the other anode material, or by depositing the other anode material on the carrier device by plating.
It is also possible to produce multilayered anodes.

On the other hand, it is clear that all of the above methods make it possible to produce multi-layer anodes with all cross-section and length characteristics.

1 to 3, the carrier device 1
Figure 3 shows an anode produced by a carrier device loaded into a suitable ingot mold or chill or mould, not shown, having a greater negative electrochemical potential than the material making up the marine structure to be protected. The outer coating is formed by casting the anode material 2.

The coated carrier device is then loaded into another suitable ingot mold or chill or mold, not shown, to cast an anode material 3 having a negative electrochemical potential greater than that of the anode material 2. The outer coating is formed by embedding.

[Brief description of drawings]

FIG. 1 is a perspective view of a consumable anode for corrosion resistance protection of marine structures made in accordance with the present invention.

2 is a vertical cross-sectional view taken along the center of the anode of FIG.

3 is a front cross-sectional view taken along the line AA in FIG.

[Explanation of symbols]

 1 Carrier device 2, 3 Anode material

Claims (5)

[Claims] 1. A corrosion resistant protection of a marine structure comprising a carrier device provided with an outer coating made of an anode material having a greater negative electrochemical potential than the material of which the marine structure is protected. In a consumable anode, the corrosion protection of marine structures, characterized in that the anode is provided with an outer coating made of another anode material having a greater negative electrochemical potential than the anode material. Consumable anode for. 2. A consumable anode according to claim 1, characterized in that the anode material coating the outside of the carrier device is composed of an aluminum alloy. 3. A consumable anode according to claim 1, characterized in that the anode material coating the outside of the carrier device is composed of a zinc alloy. 4. The consumable anode according to claim 1, wherein the other anode material is composed of a magnesium alloy. 5. A method for producing a consumable anode for protecting the corrosion resistance of marine structures according to any one of claims 1 to 4, wherein the anode material forming the outer coating of the anode carrier device is an ingot. Corrosion resistance of offshore structures, characterized by casting into a mold or chill or mould, and casting said other anode material into another ingot mold or chill or mould around the anode formed in the previous step How to make a consumable anode for protection.