JPS63294972A - Method for preventing corrosion of steel structure - Google Patents

Abstract

PURPOSE:To improve coating efficiency by keeping the surface of a steel structure present in the air in a wet state and carrying out anticorrosive treatment by coating. CONSTITUTION:The surface of a steel structure to be coated is pretreated by spouting a high-speed jet of water or shooting sand together with a high- speed jet of water. The pretreated surface is kept in a wet state by feeding a flow of water or putting a wet cloth and the structure is coated with hydraulic paint or putty. Thus, sure coating can be carried out.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for preventing corrosion of underwater steel structures using an underwater paint or an underwater curing putty. This relates to pretreatment performed before construction.

[Conventional technology]

In recent years, steel structures such as 11 oil drilling rigs or oil stockpile purges associated with offshore development, offshore plants, ships, etc., steel sheet piles and other steel structures used for seawall construction, etc., and bridge piers of large tanks constructed offshore. Although the construction and construction of underwater structures on the sea level is increasing, it is almost impossible to move these steel structures from the installation area for maintenance purposes. Consequently, problems such as anticorrosive coating, cleaning, and maintenance of these marine steel structures have arisen, and the necessity of maintenance at sea has become a major issue.

Conventionally, the method for painting submerged areas and splash zones of ships and underwater structures is to apply an underwater curing paint or putty using a brush, spatula, etc. after applying a base treatment. At this time, the surface treatment includes 2-I cleaning, which is just scraping off floating rust, etc., a method of spraying high-speed water to remove rust and scale, and a method of mixing sand into the high-speed water. There are methods such as spraying it onto the steel surface.

However, when applying an underwater curable paint or putty with a brush or spatula after applying the above-mentioned surface treatment and adjusting the steel surface, it is necessary to apply underwater curable paint or putty to not only seawater but also the tidal and splash zones of underwater structures. The parts that are in contact with the air and exist in the atmosphere are in a highly corrosive environment, so it is virtually impossible to paint them. Moreover, even if it can be painted, the painting efficiency will be extremely poor.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is to eliminate the above-mentioned difficulties of the conventional underwater painting method, and more specifically, to reliably and effectively apply it to steel surfaces existing in the air such as tidal areas and splash zones. The objective is to develop a coating method that allows easy coating.

[Means for solving problems]

The above-mentioned problem arises when painting the steel surface of an underwater part of a ship or underwater structure with an underwater curing paint or putty. This problem can be solved by substantially bringing the surface of the object to be coated into a 6i wet state after performing the conventional pre-treatment and before applying the underwater curable paint or putty to the object.

[Structure and operation of the invention]

One of the major features of the present invention is that it is aimed at the steel surfaces that exist in the submerged parts of this type of underwater steel structure, and another feature is that the steel surfaces are treated after cleaning and before painting. During this period, the material should be kept substantially moist.

Here, "existing in the air" refers to a part that is affected by moisture from seawater, lakes, and rivers, and also comes into contact with the air. Examples include so-called tidal zones and splash zones caused by water increases and droughts.

In addition, "kept in a moist state" refers to a state in which water is substantially present on the surface of the object to be coated and there is little or no contact with air. It is also possible to apply water to the surface of the object to be coated with a water gun-like stream of water that is produced by passing water through a pipe with numerous holes, or by applying water to water-retaining cloth or paper. An example of such means is applying the coating material to the object in a state where the coating material is contained therein. It can also be achieved by combining 2M or more of these methods, as long as the surface of the object to be coated is in a substantially wet state.

In the present invention, it is desirable to keep the surface of the object to be coated in the above-mentioned wet state for the entire period from cleaning to painting, but the effect is still sufficient even when the surface is kept wet for most of the above-mentioned period. be. This "substantially large part" refers to a period during which even if the material comes into contact with air, the adverse effects thereof can be substantially ignored. Therefore, the object to be coated may be in contact with the air for a short period of time to the extent that there is no substantial adverse effect.

In addition, in the present invention, it is most preferable that the entire surface of the object to be coated be in a fi-shoulder state, but some portions that come into contact with air may remain as long as there is no substantial adverse effect due to contact with air. .

Note that the underwater steel structure of the present invention refers not only to a steel structure that exists underwater, but also to a steel structure that exists on water or on land.

In the present invention, by performing the above-mentioned wet treatment, it is possible to apply an underwater curable paint or an underwater curable putty extremely easily.

The reason for this is assumed to be as follows. The surface of the object to be painted becomes clean through cleaning treatment, but if painting is performed immediately after this, the painting can be done successfully because the painting is done in a clean state. It is practically impossible to paint, and there is a certain period of time. In this case, the denatured and corroded substances formed on the surface of the steel due to seawater, etc., become hard and dense when they come into contact with the air, and remain without being removed during painting, effectively preventing the painting from occurring. It becomes difficult to do. However, according to the research of the present inventor, by keeping the surface of the object to be coated in a moist state after cleaning,
The generation of the above-mentioned modified and corrosive substances is significantly suppressed, and even if they do occur, these obstacles will not become hard and dense objects but will be in a colloidal state, so due to the viscosity of the paint itself during painting, It has been found that colloidal obstructions are removed from the surface of the object to be coated, exposing a clean surface, which allows the paint to adhere reliably. Therefore, it is assumed that this is the reason. As described above, since the paint reliably adheres to the surface of the object to be coated even in the spray zone above the water surface where corrosion is severe, it is presumed that painting can be easily carried out by ordinary means.

Of course, after wet treatment and before painting, scrubbing with a brush or the like to remove denatured and corroded substances from colloidal steel will further improve workability.

As the underwater curable paint or underwater curable putty used in the present invention, any of those conventionally used in this type of field can be used. For example, epoxy resin as the main ingredient, polyamide resin, modified aromatic family polyamines,
Underwater-curable paints or putty that uses modified aliphatic polyamines, double S-ring polyamines, alicyclic polyamines, etc. as curing agents, and underwater-curable paints or putty that use unsaturated polyester resin as a base material, etc. can be exemplified as a representative example. Also, as a means of applying this paint or putty, the usual means of painting on land can be widely adopted.
For example, a typical example is painting with a spatula or a trowel.

The effects of the present invention will be explained in more detail with reference to Examples below.

Example 1 9am x 300 layer layer x 3 with sheet pigment
Immediately after immersing a 00s+m steel plate in 3% saline solution, it was pulled out of the water, and 3% saline solution was continuously sprayed in the form of a mist.
After making the steel surface uniformly wet and keeping it as it is for 4 hours, use a commercially available brush to rub the wet steel surface, and then use a commercially available paint brush to measure the dry film thickness of the water-curable paint. I painted it so that it was hl.

The underwater curable paint used here is a commonly used epoxy resin based underwater curable paint, and its composition is shown in Table 1.

In addition, the amount of spraying 3% saline is 1 to 6 gr/rr.
It was r sin.

Table 1 Example 2 In Example 1, the composition of the underwater curable paint was as shown in Table 2, and the wet treatment method was to cover it uniformly with water-wet gauze, and to apply gauze. One end of the steel was immersed in water to keep the entire steel surface in a 6i wet state at all times, and the rest of the steel surface was treated in the same manner as in Example I.

Table 2 Comparative Example 1 In Example 1, the same treatment as in Example 1 was performed except that the 3% saline solution was not sprayed.

Comparative Example 2 The same treatment as in Example 2 was carried out except that the 3% saline solution was not sprayed.

Various physical properties were measured for each of the obtained coated objects.

The results are shown in Table 3 below.

Paint workability The standards for painting workability are shown below.

O...The paint attached to the brush will adhere to the steel surface just by touching it, and the brush can be applied well.

△・・・・・・It will stick if you rub it a few times, but the brush handling is very poor.

×...Even if you rub it several times, it hardly sticks.

<Adhesive strength> After being immersed in 3% saline for 6 months, it was taken out and the tensile adhesive strength was measured using an adhesin tester.

Cohesive Failure Rate of Coating Film> The adhesion area ratio of the resin in the destroyed area was determined by calculation for the measurement area in the above adhesive strength measurement.

<Occurrence of rust> The presence or absence was visually observed.

Table 3 (that's all)

Claims (2)

[Claims] (1) After cleaning the steel surface existing in the aerial part of an underwater steel structure, when applying an anti-corrosion coating with an underwater-curing paint or an underwater-curing putty, it is necessary to A method for preventing corrosion of steel structures in water, characterized by keeping the steel surface present in the part in a wet state. (2) The anticorrosion method according to claim 1, characterized in that when maintaining the wet state, the wet state is maintained for almost the entire period from after cleaning to when anticorrosive coating is applied.