JPH0860039A - Temporary anticorrosive coating composition - Google Patents

Abstract

PURPOSE: To obtain a temporary anticorrosive coating composition which can provide a coating film excellent in weldability and corrosion resistance and capable of preventing formation of defects such as pits and blow holes even when the welding is performed at a high speed. CONSTITUTION: This composition comprises a siloxane binder, a zinc powder as a pigment, a source of ferric oxide (Fe2 O3 ) as a pigment other than the zinc powder and a molybdenum compound (molybdenum is contained).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a primary rust preventive coating composition (shop primer) used in a steel material pretreatment carried out in a steel material processing process such as a ship, an offshore structure, a plant, a bridge, a land tank, etc., and more specifically, Is a pit (through hole) even if welding is performed at a high speed of 100 cm / min or more.
Inorganic zinc primary anti-corrosion paint that can suppress the occurrence of defects such as air bubbles and blowholes (inner bubbles), retain the excellent anticorrosion effect that zinc originally has, and have excellent weldability and anticorrosion properties. It relates to a composition.

[0002]

BACKGROUND OF THE INVENTION Conventionally, there is a primary rust preventive paint applied to the surface of steel for the purpose of temporarily preventing rusting during the construction of large steel structures such as ships, bridges and plants.

As such a primary anticorrosive coating composition,
Organic primary anticorrosion paints such as wash primer, non-zinc epoxy primer and epoxy zinc rich primer, and inorganic zinc primary anticorrosion paint using a siloxane-based binder are known. Of these primary anticorrosion paints,
The inorganic zinc primary anticorrosive coating composition having excellent weldability is most widely used.

The inorganic zinc primary anticorrosive coating composition has a small amount of gas generated during welding and is excellent in weldability.
There is a demand for even faster welding, and in order to meet this demand, it is necessary to suppress the vaporized gas pressure of zinc (melting point 419 ° C, boiling point 930 ° C) that causes pits and blowholes during welding. . Zinc dust has a melting point of iron of 15 during welding.
When exposed to heat of 30 ° C. or higher, zinc may be rapidly vaporized and defects such as pits and blow holes may occur in the weld bead. In order to solve such a problem, a method of reducing zinc dust in the primary anticorrosive coating composition is conceivable, but a method of reducing the amount of zinc dust makes it possible to speed up welding, but has anticorrosive properties. However, there is a problem that

Further, zinc is rapidly oxidized when it exceeds the melting point by heating, so that the corrosion resistance after heating is significantly reduced. In addition, in the application specification of Japanese Patent Application No. 4-272441, the inventors of the present invention, as a primary rust preventive coating composition capable of preventing oxidation of zinc due to heating during welding, include a silicon-based inorganic binder, zinc. A primary anticorrosive coating composition containing powder and a molybdenum compound is proposed. However, the primary anticorrosive coating composition described in the specification of this application cannot be used for high-speed welding with a welding speed of 100 cm / min or more.

Therefore, even if welding is performed at a high speed as described above, it is possible to suppress the occurrence of defects such as pits and blowholes, and to maintain the excellent anticorrosion effect originally possessed by zinc even after heating. The advent of a primary rust-preventive coating composition that has both excellent weldability and anticorrosion properties is desired.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems associated with the prior art. Even when welding is performed at a high speed of 100 cm / min or more, defects such as pits and blow holes are generated. It is an object of the present invention to provide a primary rust-preventive coating composition having excellent weldability and anticorrosiveness, which can suppress the above-mentioned, and can retain the excellent anticorrosive effect that zinc originally has even after heating. .

[0008]

SUMMARY OF THE INVENTION A primary anticorrosive coating composition according to the present invention comprises a siloxane-based binder (a) and zinc powder (b) as a pigment.
And ferric oxide (Fe) as a pigment (c) other than zinc dust
₂ O ₃ ) source and a molybdenum compound (including molybdenum metal).

[0009]

DETAILED DESCRIPTION OF THE INVENTION The primary anticorrosive coating composition according to the present invention will be specifically described below. The primary anticorrosive coating composition according to the present invention comprises a vehicle which is a solution of a siloxane-based binder (a), and a paste containing a pigment, an anti-settling agent, an organic solvent and the like.

Specific examples of the siloxane-based binder (a) used in the present invention include tetramethyl orthosilicate, tetraethyl orthosilicate, tetra-n-propyl orthosilicate, tetra-i-propyl orthosilicate, and tetra-orthosilicate. n-butyl orthosilicate, tetra
Examples thereof include alkyl silicates such as -sec-butyl orthosilicate, methyl polysilicate and ethyl polysilicate, methyltrialkoxysilanes such as methyltrimethoxysilane and methyltriethoxysilane, and initial condensation products thereof. Among them, ethyl silicate 40 (manufactured by Nippon Colcoat Co., Ltd.), which is an initial condensate of tetraethyl orthosilicate, is most preferable, and it is used after being partially hydrolyzed. Further, silica sol may be used together.

The zinc dust (b) used in the present invention acts as an anticorrosion pigment, but it is a commonly used zinc dust, and zinc dust having an average particle diameter of 2 to 15 μm is preferable. .

The zinc powder (b) is preferably 30 to 80% by weight, more preferably 40 to 7%, when the total of the zinc powder and the pigment (c) other than zinc powder described later is 100% by weight.
Used in an amount of 0% by weight.

In the present invention, a ferric oxide (Fe ₂ O ₃ ) source is used as the pigment (c) other than zinc dust, and as the ferric oxide source, specifically, ferric oxide, Further, examples thereof include iron powder that produces ferric oxide during welding, iron-containing components, iron-containing minerals, and the like.

As the iron-containing component, specifically, Fe
_{O, Fe 2 O 3, Fe} 3 O 4, etc. FeO · OH · nH ₂ O and the like. Examples of the iron-containing minerals include rock-forming minerals containing hematite, magnetite, maghemite, or sand iron, such as hematite, cassite, and magnetite.

Examples of the pigment (c) other than zinc dust include extender pigments, anticorrosion pigments, and coloring pigments in addition to the above-mentioned ferric oxide source. Specific examples of the extender pigment include talc, mica, clay, silica powder, zinc white, alumina, and feldspar.

As the anticorrosion pigment, there are used phosphate-based, borate-based, and molybdate-based anticorrosion pigments other than the molybdenum compound-based pigments described later. As the color pigment, a usual color pigment for paints is used.

The above-mentioned ferric oxide sources are used alone or in combination in powder form. The ferric oxide source is
When the total amount of the zinc powder (b) and the pigment (c) other than zinc powder is 100% by weight, it is preferably 5 in terms of Fe ₂ O _3.
It is used in an amount of ˜65 wt%, more preferably 10-40 wt%. In addition, the weight ratio [zinc dust / ferric oxide source] of zinc dust (b) to the ferric oxide source in terms of Fe ₂ O ₃ is 1 /
0.1 to 1 / 2.5, preferably 1 / 0.2 to 1/2,
More preferably, it is 1 / 0.3 to 1/1. When the amount of the ferric oxide source used and the weight ratio [zinc dust / ferric oxide source] of the zinc dust (b) and the Fe ₂ O ₃ equivalent ferric oxide source are in the above ranges, Even if welding is performed at high speed, it is possible to obtain a primary rust-preventive coating composition which can suppress the occurrence of defects such as pits and blowholes and has excellent corrosion resistance.

In the primary rust preventive coating composition according to the present invention, since the ferric oxide after welding is magnetic,
Ferric oxide absorbs the vaporized gas of zinc generated by the high temperature during welding and absorbs zinc ferrite (Z
nO.Fe ₂ O ₃ ).

Zn + 1 / 2O ₂ + Fe ₂ O ₃ → ZnO.Fe ₂ O ₃ As described above, Fe ₂ O ₃ absorbs the vaporized gas of Zn and forms zinc ferrite at a high temperature. The zinc gas pressure in the high temperature range exceeding the melting point is suppressed, and the formation of pits, blow holes, etc. is suppressed. Therefore, in the primary anticorrosive coating composition according to the present invention, it is possible to speed up welding at a welding speed of 100 cm / min or more without reducing the amount of zinc dust used, that is, without lowering the corrosion resistance. .

Further, in the present invention, a molybdenum compound is used as an antioxidant of zinc. Specific examples of the molybdenum compound include molybdenum metal, molybdenum oxide, molybdenum sulfide, molybdenum halide, molybdic acid and phosphorus. Molybdic acid, silicomolybdic acid, molybdic acid alkali metal salt, phosphomolybdic acid alkali metal salt, silicomolybdic acid alkali metal salt, molybdic acid alkaline earth metal salt, phosphomolybdic acid alkaline earth metal salt, silica Alkaline earth metal salts of molybdic acid,
Manganese salt of molybdic acid, manganese salt of phosphomolybdic acid, manganese salt of silicomolybdic acid, basic nitrogen-containing compound salt of molybdic acid, basic nitrogen-containing compound salt of phosphomolybdic acid, basic nitrogen-containing compound of silicomolybdic acid Examples include salt.

These molybdenum compounds are used alone or in combination in powder form. The molybdenum compound is preferably 0.5 to 20% by weight, and more preferably 1.5% by weight in terms of MoO ₃ , when the total of the zinc powder (b) and the pigment (c) other than zinc powder is 100% by weight. Used in an amount of -10% by weight. When the amount of the molybdenum compound used is in the above range, it is possible to prevent the oxidation of zinc even if the welding temperature is the melting point of zinc or higher, and it is possible to maintain the excellent anticorrosion property that zinc originally has. it can.

The primary anticorrosive coating composition according to the present invention contains an anti-settling agent such as an organic bentonite type, a polyethylene oxide type, a silica fume type, an amide type. Also,
As the organic solvent that dissolves the siloxane-based binder (a), alcohol-based, ester-based, ketone-based, aromatic glycol-based solvents or the like may be used alone or in combination.

In the primary rust-preventive coating composition according to the present invention, from the viewpoint of weldability, it is desirable to eliminate components including crystal water and organic substances as much as possible. The primary anticorrosive coating composition according to the present invention can be prepared according to a conventional method. For example, the liquid component containing the siloxane-based binder (a) and the paste containing the other powder component may be stored in separate containers, and the liquid component and the paste may be mixed immediately before use. In addition, a part or all of powder components other than components such as zinc dust that reacts with the siloxane-based binder (a) are dispersed in a liquid component containing the siloxane-based binder (a), and immediately before use, the mixture is mixed with the mixture. The remaining powder components may be mixed.

[0024]

The primary anticorrosive coating composition according to the present invention comprises a siloxane-based binder (a) and zinc powder (b) as a pigment.
And ferric oxide (Fe) as a pigment (c) other than zinc dust
₂ O ₃ ) source and molybdenum compound (including molybdenum metal) are contained, so that it has excellent weldability and corrosion resistance,
Even when welding is performed at a high speed of cm / min, it is possible to suppress the occurrence of defects such as pits and blow holes, and it is possible to maintain the excellent anticorrosion effect that zinc originally has even after heating.

Therefore, the primary rust preventive paint composition according to the present invention can be suitably used as a primary rust preventive paint for high speed welding. Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[0026]

[Comparative Examples and Examples 1 to 7] [Preparation of Main Agent for Primary Antirust Coating] Ethylsilicate 40
(Nippon Colcoat Co., Ltd.) 350 g, industrial ethanol 1
50 g, deionized water 50 g, and 35% hydrochloric acid 0.5 g
Was charged in a container and kept at 50 ° C. for 3 hours with stirring, and then 449.5 g of IPA (isopropyl alcohol) was added to prepare a main agent. This main agent was used commonly in Comparative Examples 1 and 2 and Examples 1 to 7.

[Preparation of Paste for Primary Anticorrosion Paint] Pigments other than zinc dust, anti-settling agent and solvent were placed in a polyethylene container, glass beads were added, and the mixture was shaken in a paint shaker for 1 hour, and then zinc dust was added. Was added and shaken for another 5 minutes to disperse the pigment. The glass beads were removed using an 80 mesh net to prepare a paste. Comparative example,
Table 2 shows the paste compositions of the examples.

[Testing / Evaluation Method for Anticorrosion and Weldability] (1) Anticorrosion Main ingredient and paste were thoroughly mixed at a predetermined mixing ratio, and
A 0 mm × 150 mm × 2.3 mm sandblast plate was coated with air spray so that the dry film thickness was 15 μm, and dried in a room for 7 days to obtain a test piece for a Bakuro test. Air temperature and relative humidity during painting and indoor drying are (24 ℃, 75%), (17-25 ℃, 55-75%), respectively.
Met.

From the test pieces obtained as described above, an unheated test piece and a test piece heated at 800 ° C. for 2 minutes in an electric furnace were prepared, and these test pieces were prepared by the Otake Research Laboratory (Seto Inland Sea). (Overseas regions of Japan) were subjected to backfloor with a backfloor stand installed on the south surface 45 ^O , and the time until rusting and the degree of rusting were evaluated on a scale of 5 to 1 below.

Evaluation 5: No rusting at all 4: Slight rusting symptom 3: Occurrence of rusting 2: Marked rusting 1: Whole surface rusting (2) Weldability SS400 steel plate of 800 mm × 100 mm × 12 mm size sandblasted The paints of Comparative Examples and Examples were coated on the entire surface of the above in the same manner as the test piece for the Bakuro test so that the dry film thickness was 15 μm. As shown in FIG. 1, one of two identical test pieces is used as a lower plate 1 and the other one is used as an upper plate 2 and is erected at the center of the lower plate 1, and is formed by the upper plate 2 and the lower plate 1. Horizontal fillet welding was carried out at the corners. Reference numeral 3 in the drawing is a welding bead.

Tandem method (welding speed 12
Pit occurrence rate (pieces / m) and blowhole occurrence rate (total length of maximum width of all bubble cross section in weld fracture surface / welding length × 100%) were evaluated.
The welding was performed by welding the first bead and then allowing it to cool and then welding the second bead, and only the second bead was evaluated. Table 1 shows the welding conditions of the tandem method.

The evaluation results are shown in Table 3.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

The following can be understood from Tables 2 and 3. The comparative example is an example in which the amount of zinc used in the primary anticorrosive paint is a standard amount. The non-heated test piece of the comparative example showed antibacterial corrosion resistance for 6 months, but the test piece heated at 800 ° C. generated considerable spot rust after 2 months. Further, in the comparative example, welding defects frequently occurred.

In Example 1, it was recognized that the corrosion resistance and weldability of the heated test piece were improved as compared with the comparative example. In Examples 2, 3 and 4, the corrosion resistance of the heated test pieces,
The weldability was significantly improved.

In Example 5, the best results were obtained. The antibacterial corrosion resistance was hardly reduced even in the heated test piece, the weldability was free of pits, and the blowholes were few.

In Examples 6 and 7, primary rust-preventive coatings were used in which the amount of zinc used was less than the standard amount. The corrosion resistance of the unheated test piece using such a coating is inferior to that of Comparative Examples and Examples 1 to 5, but it is practically 3 by using a black valve stem (magnetite).
The corrosion resistance of the heated test piece was not deteriorated, and the corrosion resistance was better than that of Comparative Example and Example 1. Further, in Examples 6 and 7, almost no welding defects occurred.

[Brief description of drawings]

FIG. 1 is an explanatory perspective view of horizontal fillet welding in Examples and Comparative Examples.

[Explanation of symbols]

 1 ・ ・ ・ Lower plate 2 ・ ・ ・ ・ ・ Upper plate 3 ・ ・ ・ Weld beads

Claims (6)

[Claims] 1. A siloxane-based binder (a), zinc powder (b) as a pigment, and ferric oxide (Fe) as a pigment (c) other than zinc powder.
₂ O ₃ ) source and a molybdenum compound (including molybdenum metal), a primary rust preventive coating composition. 2. The amount of the ferric oxide source is 5 to 65% by weight based on Fe ₂ O ₃ when the total pigment component is 100% by weight. The primary anticorrosive coating composition described. 3. The amount of the molybdenum compound is 0.5 to 20% by weight based on 100% by weight of all pigment components in terms of trioxide (MoO ₃ ). The primary anticorrosive coating composition according to 1. 4. The weight ratio [zinc dust / ferric oxide source] of zinc dust (b) to ferric oxide source in terms of Fe ₂ O ₃ is 1 / 0.1.
It is 1 / 2.5, The primary rust-preventive-coating composition of Claim 1 characterized by the above-mentioned. 5. The ferric oxide source is FeO, Fe ₂ O ₃ ,
At least one powder selected from the group consisting of powders of iron-containing components such as Fe ₃ O ₄ and FeO · OH · nH ₂ O; iron powders; and rock-forming mineral powders containing hematite, magnetite, maghemite or sand iron. The primary anticorrosive coating composition according to claim 1, wherein the primary anticorrosive coating composition is present. 6. The molybdenum compound is molybdenum metal, molybdenum oxide, molybdenum sulfide, molybdenum halide, molybdic acid, phosphomolybdic acid, silicomolybdic acid, alkali metal salt of molybdic acid, alkali metal salt of phosphomolybdic acid, Alkali metal salt of silicomolybdic acid, alkaline earth metal salt of molybdic acid, alkaline earth metal salt of phosphomolybdic acid, alkaline earth metal salt of silicomolybdic acid, manganese salt of molybdic acid, manganese salt of phosphomolybdic acid, At least one powder selected from the group consisting of a manganese salt of silicomolybdic acid, a basic nitrogen-containing compound salt of molybdic acid, a basic nitrogen-containing compound salt of phosphomolybdic acid, and a basic nitrogen-containing compound salt of silicomolybdic acid. Primary rust preventive according to claim 1, characterized in that it is a component in the shape of Charge composition.