JP2004299979A - Surface preparation material for steel and method of surface- preparation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface preparation material for actively removing harmful anion such as chloride ion which can not be removed physically such as by blast treatment in repainting a corroded steel surface. <P>SOLUTION: An anion adsorbent such as calcium-aluminum combined hydroxide which is not consumed by the reaction with cement is incorporated in a cement-based surface preparation material using a water-based epoxy resin as a liquid admixture and the surface preparation in repainting is performed using the surface preparation material to suppress the occurrence of steel corrosion. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a technical field of a base adjustment material excellent in rust prevention effect applied as a base adjustment material to a steel material surface constituting a steel structure such as a bridge, a tank, a pier, a steel frame, a roof, and the like.
[0002]
[Prior art]
BACKGROUND ART Conventionally, the surface of a steel structure such as a bridge has been painted for the purpose of preventing corrosion and ensuring the appearance of the steel, assuming long-term use. In this case, since the durability of the coating film is shorter than the expected service life of the steel structure, a plurality of repainting operations are required. Investigation results of the coating deterioration state of the coating system for general environment have confirmed that the deterioration progress of the repainted coating film is faster than that of the new coating film. This is considered to be due to the fact that the coating film on the rust surface remaining at the time of adjusting the base material deteriorates at an early stage, considering that the coating material generally occurs even when there is no difference in the applied coating material.
This is because, as shown in FIG. 1, for example, as shown in FIG. 1, anions, which are factors (salts and the like) that promote corrosion in the environment, are concentrated near the interface between the steel and the rust layer to form a nest. . The nest is a corrosion cell formed on the steel surface due to the corrosion of steel, and the anions are electrochemically captured and concentrated on the anode part. The corrosion reaction is not suppressed. For this reason, durability will be inferior compared with a newly-installed coating film. Therefore, when performing corrosion protection such as painting, it is necessary not only to remove the rust layer, but also to effectively remove corrosion-promoting anions that are concentrated at the interface between the steel and the rust layer.
By the way, the base adjustment (base adjustment) of the corroded part in the repainting is different from the removal of the rust generated in a short term as in the case of the new painting, and is a work of removing the rust layer generated over a plurality of years. Use a blasting device to remove such rust layers and nests, or physically remove such degraded parts using a power tool such as a disc sander or air hammer and a hand tool such as a hammer or scraper. The method is generally adopted. However, it is said that the anions in the nest formed at the interface between the steel and the rust layer cannot be completely removed by the physical removal operation as described above.
Therefore, conventionally, a method of applying a paint containing a rust-preventive pigment such as zinc as a base material of a repainting system has been carried out to prevent rust, but this method does not actively remove the anion. Therefore, the effect of suppressing the generation of rust on the steel surface is poor, and in the case of repainting, rust may occur in a shorter period of time than in the case of new coating. Therefore, a coating material containing a copolymer of an alkyl methacrylate is applied as an undercoating material to thereby enhance the rust prevention effect (Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-42485 [Problems to be Solved by the Invention]
However, the technique disclosed in Patent Literature 1 is intended to prevent corrosion of the anion, which is a factor of rust generation, by preventing invasion of the anion from the outside, and does not remove the anion in the nest. Even if the rust-preventing effect is excellent, improvement of the durability of the repainting system cannot be expected, and there is a problem to be solved by the present invention.
[0004]
[Means for Solving the Problems]
The present invention has been completed as a result of intensive studies in view of such circumstances, and the invention according to claim 1 is characterized in that a cement-based substrate conditioning material contains an anion adsorbent, and the steel material substrate is characterized in that: It is an adjusting material.
According to a second aspect of the present invention, in the first aspect, the anion adsorbent is a calcium-aluminum composite hydroxide that is not consumed by reacting with the cement.
According to a third aspect of the present invention, in the first or second aspect, the content of the anion adsorbent is 1.0% by weight or more.
A fourth aspect of the present invention is a method for preparing a base material for a steel material, wherein a cement base material containing an anion adsorbent is applied to the steel material.
By doing so, it is possible to positively remove anions attached to the steel material surface, suppress corrosion of the steel material even in the case of repainting, and improve the durability of the paint film. As well as improving the protection of the steel itself from corrosion.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention exerts a high rust-preventing effect by positively removing anions generated at the interface between the rust layer and the steel material, thereby improving the durability of the repainting system, such as stretching of the repainting cycle. It was done. The base adjusting material is a material to which an anion adsorbent is added. Examples of such an anion adsorbent include calcium-aluminum composite hydroxide and magnesium-aluminum composite water which are not consumed by reacting with cement. Oxides are suitable, and specific examples thereof include hydrocalmite and hydrotalcite. Hydrocalmite has a high ability to adsorb salts, which has a particularly great effect as a factor promoting corrosion of steel. The base adjustment material according to the present invention may be used not only at the time of repainting but also at the time of new coating.
[0006]
The present invention employs a cement-based base conditioner. As the cement employed here, for example, commonly known cements such as ordinary Portland cement, alumina cement, and early-strength cement can be employed.
As the base composition, an epoxy resin is generally used, but a commonly known base composition such as an acrylic resin can be used.
Furthermore, the base adjustment material may be a material to which an antifoaming material such as octyl alcohol is added, or a material to which a filler such as calcium carbonate, kaolin or the like is added to improve coating workability.
[0007]
The amount of the anion adsorbent added to the base material is preferably in the range of 4.0% by weight or more, more preferably 8% by weight or more. If the added amount of the anion adsorbent is small, rust is generated on the surface of the steel material, and if the added amount is large, the blistering resistance and the like of the paint film such as the top coat and the middle coat are reduced.
[0008]
Hereinafter, the present invention will be described in more detail with reference to experimental examples.
[0009]
[Preparation of specimen]
A cold-rolled steel plate (SS40) having a length of 100 mm and a width of 100 mm (mm) and a thickness of 1 mm was prepared as a steel plate for a specimen, the surface of the steel plate was degreased, and then quenched with a mesh # 120 sander. It was created. The test piece was immersed in artificial seawater at 40 ° C. for 48 hours, and then left standing in a thermostat at 40 ° C. for 50 days. During this standing, artificial seawater was sprayed every 24 hours to generate rust. I let it. It has already been confirmed by other experiments that the condition of the rust generation is substantially the same as the condition where the steel material was exposed to the undersea tunnel for one year. Then, the generated rust of the steel sheet was removed with a scraper until the rust became invisible to the naked eye, the stain was removed with a solvent, and then washed with water and dried to obtain a specimen.
[0010]
[Coating experiment of specimen]
The surface of the obtained specimen was coated with a base adjustment material under the conditions shown in the table in FIG. 2, allowed to dry naturally for 3 hours, and then coated with the same base adjustment material again. Then, with respect to the case where rust was generated on the test sample, rust generation was attempted under the same conditions except that the standing period was one month. The number of specimens used in each experiment was three, and the results described later were averaged. The base adjustment material is a cement-based base adjustment material containing an aqueous epoxy resin as an admixture, and a hydraulic powder in which cement and calcium carbonate are mixed at a weight ratio of 1: 1; And an admixture (reactive curing agent) that is a main component of the resin. Examples of such a material include "Register Under" manufactured by Asahi Bond Industrial Co., Ltd. As an anion adsorbent, hydrocalumite (salt adsorbent) having a high salt-adsorbing ability was used, and there is "Solcut" manufactured by Nippon Chemical Industry Co., Ltd.
[0011]
[Results and discussion]
The result of observing the surface of the exposed specimen with the naked eye is shown in FIG. 2, and the corrected natural potential of the applied coating film was obtained. The result is shown in FIG. The method of obtaining the corrected natural potential is described in Japanese Patent No. 3096240. It has been confirmed that the degree of corrosion of the steel material can be known from the corrected natural potential determined in the same manner as in the method of the patent, and this is an index of the degree of acceleration of rust generated in the test specimen.
[0012]
As a result of observing the state of the surface of the specimen with the naked eye, it was confirmed that cracks had occurred in the specimen without an anion adsorbent (test number 1 = blank). The occurrence of rust was confirmed. On the other hand, the corrected natural potential is -496 millivolts (mV), and in the state of the corrosiveness IV or V, an inflatable rust is generated from the relationship between the corrected natural potential and the degree of corrosion shown in FIG. . When the coating film was peeled off, it was confirmed that rust was generated on the entire surface of the specimen.
On the other hand, the one containing the salt adsorbent at a weight ratio of 5/300 (= 1.67% by weight) (Test No. 2) had a good appearance. The corrected spontaneous potential was -350 mV, and the corrosion degree was in the category of judgment of III. When the coating film was peeled off, spot rust was formed on the surface of the test piece, but it was confirmed that rust generation was clearly suppressed as compared with the case of Test No. 1.
Furthermore, the corrected natural potential of the sample containing the salt adsorbent in a weight ratio of 10/300 (= 3.33% by weight) (test number 3) was -272 mV, and the corrosion degree was in the category of II. After the peeling of the coating film, it was visually confirmed that slight rust was generated on the surface. If the occurrence of rust is at this level, it is judged that there is no problem in practical use.
The corrected natural potential of the sample containing the salt adsorbent in a weight ratio of 30/300 (= 10.0% by weight) (test number 4) was -209 mV, and the corrosion degree was in the category of I without rust. In addition, the occurrence of rust after the coating film was peeled was not visually observed, and it was confirmed that the occurrence of rust was clearly suppressed.
Furthermore, the corrected natural potential of a sample containing a salt adsorbent in a weight ratio of 50/300 (= 16.7% by weight) (test number 5) was -204 mV, and the corrosion degree was in the range of I without rusting. Further, it was confirmed that rusting after peeling of the coating film was not visually observed, and the occurrence of rust was suppressed. Since the result was almost the same as that of Test No. 4, it was judged that up to about 10.0% by weight was appropriate as an addition amount.
[0013]
【effect】
As described above, in the embodiment of the present invention, by including the anion adsorbent in the base adjustment material, the anion in the nest generated at the interface between the rust layer and the steel material can be positively removed. Therefore, even in the case of repainting, corrosion of the steel material is suppressed, the durability of the coating film is improved, and the steel material itself can be protected from corrosion.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a state of a corrosion cell.
FIG. 2 is a table showing test conditions and a state when the results are visually observed.
FIG. 3 is a graph showing a measured self potential.
FIG. 4 is a table showing the relationship between the corrected natural potential and the degree of corrosion.

Claims (4)

A steel base preparation material comprising a cement base preparation material containing an anion adsorbent. 2. The base preparation material for steel according to claim 1, wherein the anion adsorbent is a calcium-aluminum composite hydroxide that is not consumed by reacting with the cement. 3. The steel base adjustment material according to claim 1, wherein the content of the anion adsorbent is 1.0% by weight or more. A method for preparing a steel base material, comprising applying a cement base preparation material containing an anion adsorbent to the steel material.

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