JPS604912B2 - Seawater corrosion protection method for structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel and outstanding method for corrosion protection of structures such as steel used in seawater.

Conventionally, structures such as wire rods used in seawater, such as fishing nets and floating breakwaters, have been made of galvanized steel wires, aluminized steel wires, and the like. However, these materials are not necessarily preferable in terms of corrosion resistance in seawater. In other words, zinc does not have very good corrosion resistance against seawater, and it is difficult to properly form a coating layer other than by plating, so the plating layer itself is inevitably thin and causes pinholes to form. It cannot be said to be sufficient as a protective layer.

This point is the same in the case of aluminum coating by plating, and even if extrusion coating is performed, conventionally pure aluminum is used in consideration of workability. In reality, however, it cannot be said that they necessarily have sufficient corrosion resistance. For this reason, an excessively designed structure with a wall thickness larger than necessary was adopted, which was unfavorable in terms of economy and efficiency. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a seawater corrosion protection method that can eliminate the problems of the conventional methods.

In other words, as a result of various trial and error experiments, the inventors discovered M
g0.1-5%, Mno. 1 to 4% Sb as necessary,
By coating the outer circumferential surface of the structure with an alloy containing 0.1% or less of Ti, V, or Cr in an individual amount or less, and the remainder consisting of mountains and unavoidable impurities, seawater can be easily absorbed. It has been found that corrosion resistance can be improved in the interior.

The lower limit of Mg and Mn was set at 0.1% because below this the effect of improving corrosion resistance disappears, and when Mg is 5% or Mn
If h exceeds 4%, the deformation resistance will increase and it will be difficult to perform intervening coating, such as extrusion coating, so it is excluded. Adding Sb, Ti, V or Cr as necessary is because Sb contributes to improving corrosion resistance in seawater with chemical contamination, and Ti and V
Cr contributes to the uniform dispersion of additive elements and as a result prevents selective corrosion of the material, and Cr contributes to improving the mechanical properties of the intervening coating layer, so it is added depending on the purpose of use. It is. However, if each of these elements exceeds 0.1% alone, the purpose of their addition will be saturated, and the overall corrosion resistance will deteriorate, and workability will also deteriorate, so they are excluded. be done. To carry out these anti-corrosion methods, the above-mentioned alloy can be coated on the outer surface generally by a conventionally known extrusion coating method.

This is effective when the structure is made of wire rods, bamboo rods, pipes, etc. that have relatively simple cross-sectional shapes. In the case of extrusion, it is appropriate to use extrusion with forward tension applied. However, the processing method is not limited to these processing methods, and it is of course possible to perform the intervening coating by various methods such as rolling method, drawing method, powder compacting method, special plating method, etc., if necessary.

Table 1 shows the results of a corrosion resistance test performed on a steel wire of 2.50 for the anticorrosion method according to the present invention, a conventional example, and a comparative example.

Table 1: Corrosion resistance test of wire rod *Only marked examples are examples of the present invention, others are comparative examples ○ Good Good △
A steel wire with a rating of 2.50 for both Slightly Poor and Poor was subjected to an immersion experiment in seawater with an intervening coating layer of 100 peaks on the outer peripheral surface by bond plating in the case of the plating method and extrusion coating in the other cases.

As a result ○) With the presence of a zinc layer, the lifespan is approximately half a year.

[21 Aluminum plating has a lifespan of approximately one and a half years. '3} When extruded electrical aluminum was used, it had a lifespan of two years, but the corrosion resistance rapidly deteriorated after that.

(2) However, when the aluminum alloy according to the present invention was used as an intervening coating, even after 5 years, it still had a healthy appearance, and the results of the microscopic structure examination showed that the integrity was sufficiently maintained. However, outside the range covered by the present invention, if the concentration is low, the corrosion resistance after 5 years will cause pitting corrosion and general corrosion and deterioration will be seen, and if the concentration is high, the workability will decrease and it will be difficult to properly coat the coating. Met. However, it has been found that it is easy to coat the outer surface that comes into contact with seawater with an aluminum alloy within the range specified by the present invention, and thereby the outstanding corrosion resistance against seawater can be exhibited.

The effects on industry are significant.

Claims (1)

[Claims] 1 Mg on the outer peripheral surface of structures used in contact with seawater.
0.1-5%, Mn0.1-4% Sb, Ti as necessary
, V or Cr, in an amount of 0.1% or less by weight, with the remainder being Al and unavoidable impurities, and the alloy layer is in direct contact with seawater. Seawater corrosion protection method for objects.