JP2010018838A - Steel structure coated with aluminum alloy, and corrosion protective coating method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of inexpensively and sufficiently performing corrosion prevention of a complicated part of a steel structure on which mill coating is impossible. <P>SOLUTION: The corrosion protection method of a steel structure includes subjecting the steel structure to underecoating treatment to achieve a cleanliness equivalent to class 2 cleaning, then coating the class structure with atmospheric plasma thermal spraying so as to form a coated film having a thickness of 100 μm or more, using any of Al having a purity of 99.5 mass% or more, an Al alloy containing 1-5 mass% of Mg, or an Al alloy containing 1-1.5 mass% of Mn, and then subjecting the coated steel structure to sealing treatment using a material essentially comprising a metal alkoxide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a corrosion-resistant spray-coated steel structure of an Al alloy exhibiting excellent corrosion resistance against seawater, salt, and the like, and a method for the corrosion-proof coating.

    Steel structures undergo corrosion in an uncovered state in a natural environment. In particular, steel structures built in the marine environment are corroded significantly by seawater and sea salt particles, and therefore, usually are subjected to anticorrosion coating treatment. Typical examples include painting, plating, or resin lining.

  Since plating or resin lining treatment cannot be performed on site, it cannot be applied to complex parts that require anti-corrosion treatment after construction of steel structure joints. Although painting can be applied to the part, it is inferior in durability and corrosion resistance, and it is expensive because it requires periodic repainting.

  As another anticorrosion method, there is a method of anticorrosion spraying of Zn or Al and its alloys, which electrochemically show a lower potential than carbon steel by spraying on the surface of carbon steel (JIS H8300). These are used as anti-corrosion coatings in the clean atmosphere of nature, forming a dense and basic corrosion-resistant basic carbonate film on the surface to prevent the spray coating from being consumed. This is because when the steel material surface is exposed due to damage, the alloy film is eluted as a sacrificial anode, and an effect of preventing corrosion of the steel material can be expected.

Patent Document 1 discloses that thermal spraying is performed on a poor environment portion of a steel structure, and Patent Document 2 discloses an invention in which an outer surface of a steel pipe is coated with an Al—Mg—Zn alloy by flame spraying. No. 3 discloses an invention in which an Al—Mg alloy is sprayed by gas flame on a portion of a welded bead portion of an ERW steel pipe cut and removed. Patent Document 4 discloses an invention for spraying a Zn—Mg alloy.
JP 2001-89880 A JP 2001-279420 A JP 2002-80955 A Japanese Patent No. 3305573

  However, defects are likely to occur in the spray coating, and arc spraying according to Patent Document 2 and gas flame spraying according to Patent Document 3 have many defects in the spray coating, making it difficult to obtain sufficient corrosion resistance. Further, the thermal spray coating according to Patent Document 4 has good sacrificial anticorrosive properties, but has a problem that the corrosion resistance of the coating itself is not sufficient.

  Further, Patent Document 1 shows that thermal spraying is performed on a poor environment portion of a steel structure, but these portions are not necessarily portions where mill coating is impossible.

  In the above-described conventional technology, sufficient corrosion prevention has not been performed on a portion where mill coating is impossible.

  An object of the present invention is to inexpensively and sufficiently carry out anticorrosion of complex parts where mill coating of steel structures is impossible.

  The present invention has been made to solve the above-described problems, and has the following configuration.

  The first invention is an Al alloy containing a purity of 99.5 mass% or more, or 1 to 5 mass% Mg, after applying a base treatment that provides a cleanliness equivalent to or higher than two types of kelen to the steel structure, or Then, using any one of Al alloys containing 1 to 1.5 mass% of Mn, it is coated by air plasma spraying so as to have a film thickness of 100 μm or more, and then sealed with a metal alkoxide as a main component. It is a corrosion prevention method for a steel structure characterized by performing a hole treatment.

  The second invention uses either an Al alloy with a purity of 99.5 mass% or more, an Al alloy containing 1 to 5 mass% Mg, or an Al alloy containing 1 to 1.5 mass% Mn. It is a steel structure subjected to a sealing treatment mainly composed of an anticorrosion coating by atmospheric plasma spraying and a metal alkoxide.

  ADVANTAGE OF THE INVENTION According to this invention, the corrosion prevention of the complicated site | part of the structure where a mill coating is impossible can be implemented cheaply enough. Therefore, since it becomes possible to construct a steel structure exhibiting excellent corrosion resistance against seawater, salinity and the like, there is a remarkable effect as compared with the conventional structure when applied to an offshore structure.

The present invention will be specifically described below.
First, groundwork adjustment equivalent to or higher than the Class 2 Keren of the Japan Road Association Standard is performed on complex parts of steel structures that cannot be mill coated, such as welded joints. Next, when the substrate adjustment is completed, an Al alloy containing 99.5 mass% or more of Al, or 1 to 5 mass% of Mg, or 1 by an atmospheric plasma spraying method so that the film thickness becomes 100 μm or more. A thermal spray coating having a film thickness of 100 μm or more is formed by atmospheric plasma spraying using any one of Al alloys containing ˜1.5 mass% of Mn.

  Next, the formed sprayed coating is subjected to a sealing treatment mainly containing a metal alkoxide, particularly an alkyl silicate. Thus, long-term corrosion resistance can be ensured even in a steel structure applied to a particularly severe marine environment by the thermal spray coating formed on the complex structure portion and the sealing treatment.

  In addition, if base preparation is not implemented, the adhesiveness of a thermal spray coating and the steel material surface which is a base material will not be ensured enough. The ground treatment may be equivalent to or higher than the Japanese Road Association Standard 2 types of keren, and more preferably 1 type of Keren (Japan Road Association standard, blast treatment). Then, after finishing the base treatment, it is possible to spray one of the three types of Al and Al alloys shown above immediately and preferably within 2 hours so that the film thickness is 100 μm or more by the atmospheric plasma spraying method. preferable.

  Other spraying methods that can be applied in the field include gas flame spraying and arc spraying, but those using atmospheric plasma spraying have better corrosion resistance than other spraying methods. This is thought to be because the use of an inert gas such as nitrogen suppresses the oxidation of the thermal spray coating, but no clear reason is known.

  As a metal for forming the thermal spray coating, Al having a purity of 99.5 mass% or more, an Al alloy containing 1 to 5 mass% Mg, or an Al alloy containing 1 to 1.5 mass% Mn is used. If present, sufficient corrosion resistance and sacrificial corrosion resistance can be exhibited.

  In the case of Al, since the corrosion resistance becomes insufficient when the Al content is less than 99.5 mass%, the purity of Al needs to be 99.5 mass% or more.

  In the case of an Al alloy containing Mg, if the Mg content is less than 1 mass%, the effect of adding Mg is not observed, and the effect is saturated even if added in excess of 5 mass%.

In the case of Mn-added Al alloy, if the Mn content is less than 1 mass%, the effect of addition is not observed, and if it exceeds 5 mass%, the corrosion resistance is inferior.
The above-mentioned three types of Al alloys can exhibit the necessary corrosion resistance and sacrificial corrosion resistance.

  The film thickness of the sprayed coating needs to be 100 μm or more. If it is less than 100 μm, sufficient corrosion resistance cannot be obtained. This is presumably because the environmental barrier properties are not sufficient when the film thickness is 100 μm or less because of the pores inevitably formed in the sprayed coating.

  After spraying Al or an Al alloy, it is preferable to carry out a sealing treatment. Although the sprayed coating alone exhibits a certain degree of corrosion resistance, it is preferable to carry out a sealing treatment because the above-mentioned pores are present in the sprayed coating.

Particularly preferred as the sealing agent is a metal alkoxide represented by the general formula M (OR) n (M: metal such as Si, Ti, Al and ZrZr, R: alkyl group such as CH ₃ and C ₂ H ₅ ). In particular, those having as a main component alkyl silicate (including dimer, trimer and the like synthesized by repeating Si (OR) ₄ and hydrolysis and condensation reactions) are preferable.

  Examples of the alkyl silicate include tetraalkoxysilane, alkyltrialkoxysilane, dialkylalkoxysilane, and partial condensates thereof, but are not particularly limited, and these may be used alone or in combination. Moreover, you may make a sealing agent contain a rust preventive pigment, a coloring pigment, etc.

  The sealing treatment is preferably carried out as soon as possible after thermal spraying. After a few days after spraying, there is a high possibility that condensation will form in the sprayed coating or dust will adhere to the surface, so that the penetration of the sealing agent into the coating will be hindered and defects such as pores will likely remain. It is to become.

  As described above, it is possible to sufficiently and inexpensively carry out anticorrosion of complex parts where the steel structure cannot be mill coated.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated in detail, this invention is not limited to these.

Inventive Examples 1 to 6 and Comparative Examples 7 to 16 As shown in Table 1, substrate treatment, thermal spraying, and sealing treatment were performed on one surface of a 100 mm × 100 mm × 6 mm hot rolled steel sheet (equivalent to JIS SS400). As a sealing treatment agent, a Serratet GS seal containing an alkyl silicate (Kansai Paint Co., Ltd.) was used, and the sealing treatment was performed by mist coating so as to be about 160 g / m ² .

As a comparative example, an epoxy resin-based paint, Epomarin HB (Kansai Paint) was used, and a sealing treatment was performed by mist coating so as to be about 160 g / m ² .

  The back end was sealed with a silicon sealant to obtain a test material. This was evaluated by an accelerated exposure test using a salt spray test (SST, JIS Z2371) and a combined cycle test (CCT, JASO method), and the time until the occurrence of red rust was investigated.

  The results are shown in Table 1. The test cycle of the combined cycle test (CCT, JASO method) is as follows.

(A) Salt spray (35 ° C., 5 wt% NaCl aqueous solution) 2 hours → (b) Dry (60 ° C., 25% RH) 4 hours → (c) Wet (50 ° C., 95% RH) 2 hours → (a) Back to No. 1 to 6 are within the scope of the present invention in all of the sprayed alloy components, the spraying method, the sprayed film thickness, and the sealing treatment. Therefore, red rust occurs in both the salt spray test (SST) and the combined cycle test (CCT). The time required until 4000 hours or more was excellent in corrosion resistance.

  On the other hand, No. which is a comparative example. Nos. 7 to 9 are no. No. 10 was not subjected to sealing treatment, so No. 11 has a sprayed film thickness of less than 100 μm, so No. 12 was not an Al alloy. Nos. 13 and 14 were No. because the thermal spraying method was not atmospheric plasma spraying. No. 15 was not subjected to sealing treatment with a metal alkoxide. No. 16 was insufficient in corrosion resistance because the ground treatment of the steel material was insufficient, and the time until red rust occurred was short.

Inventive Examples 21 to 23 and Comparative Examples 24 to 26 After performing two kinds of kelen on the steel structure welded portion, as shown in Table 2, the base treatment, thermal spraying, and sealing treatment were performed. As a sealing treatment agent, Serratet GS seal (Kansai Paint) was used, and sealing treatment was performed by airless spraying so as to be about 160 g / m ² . This was exposed to the splash zone of the marine environment for 2 years. The results are shown in Table 2.

  Inventive example No. 21 to 23 are within the scope of the present invention in all of the sprayed alloy components, spraying method, sprayed film thickness and sealing treatment, so no abnormalities are observed in the appearance after the exposure test in the marine splash zone, and excellent corrosion resistance was gotten.

  On the other hand, No. which is a comparative example. No. 24 was not subjected to sealing treatment, so No. 25 was not an Al alloy. In No. 26, since the surface treatment of the steel material was insufficient, red rust was observed in the appearance after the exposure test in the ocean splash zone.

    ADVANTAGE OF THE INVENTION According to this invention, corrosion prevention of the complicated structure site | part in which the mill coating of a steel structure cannot be performed can fully be implemented cheaply. Therefore, it is possible to construct a steel structure that exhibits excellent corrosion resistance against seawater, salt, and the like, and therefore, when applied to an offshore structure, there is a remarkable effect compared to the conventional structure.

Claims (2)

  After applying a base treatment that provides a cleanliness level equivalent to or higher than two types of kelen to the steel structure, Al having a purity of 99.5 mass% or more, or an Al alloy containing 1 to 5 mass% Mg, or 1 to 1.5 mass % Of Mn-containing Al alloy is used to cover the film to a film thickness of 100 μm or more by atmospheric plasma spraying, and then a sealing process mainly including a metal alkoxide is performed. A corrosion prevention method for steel structures.   Anti-corrosion by atmospheric plasma spraying using either Al of purity 99.5 mass% or more, Al alloy containing 1 to 5 mass% Mg, or Al alloy containing 1 to 1.5 mass% Mn A steel structure that has been sealed with a coating and metal alkoxide as the main components.