JPS6241627B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a primary rust-preventing paint composition, and more particularly to a primary rust-preventing paint composition that is applied to a steel plate before processing and provides good weldability during gas shield welding. Conventionally, when constructing large steel structures such as ships, bridges, tanks, and plants, it has been necessary to prevent rust during construction, to ensure complete anti-rust coating, and to construct economically and efficiently. It is common practice to blast or pickle raw materials before processing to remove mill scale and rust, and then apply a primary anti-corrosion paint. Conventionally, the primary anti-corrosion paints used are:
Polyvinyl butyral resin - phosphoric acid based wash primer, organic resin such as epoxy resin - organic zinc-rich paint based on high concentration zinc dust, inorganic binder - high concentration zinc dust based inorganic zinc-rich paint, etc. However, organic resins such as polyvinyl butyral resin and epoxy resin decompose or burn at high temperatures, and zinc-rich paints based on high-concentration zinc dust vaporize due to the low boiling point of zinc dust, which generates gas during welding. It has the disadvantage of being prone to blowholes. In particular, in gas shield welding methods such as carbon dioxide gas welding, the cooling rate of the molten metal is faster than in shielded arc welding and submerged arc welding.
Steel plates coated with conventional primary anti-corrosion paints have the disadvantage of producing a large number of blowholes. In recent years, the use of carbon dioxide gas welding has been increasing in the shipbuilding industry, and there has been a desire to develop a primary rust-preventing paint composition that provides good weldability during gas shield welding such as carbon dioxide gas welding. On the other hand, when molten metal is solidified, a large number of pores are generated inside the metal, and it is well known that adding a deoxidizing agent reduces the number of pores. For this reason, attempts have been made to improve the weldability of coated arc welding and submerged arc welding by adding deoxidizing pigments to primary anticorrosion paints (Japanese Patent Laid-Open No. 47-8122
Even if this method was applied to carbon dioxide gas welding, good weldability was not necessarily obtained. An object of the present invention is to provide a primary rust preventive paint composition that eliminates the drawbacks of conventional primary rust preventive paint compositions and provides good weldability, particularly during gas shield welding. As a result of intensive research to achieve this objective, the present inventors found that in order to reduce the occurrence of blowholes during carbon dioxide gas welding, it is necessary to actively suppress the occurrence of blowholes by using deacidifying pigments, and at the same time, to reduce the occurrence of blowholes during high-temperature decomposition. The present invention was achieved by discovering that it is essential to suppress the generation of gas. The present invention is coated on a steel plate using a gas shield welding method, and contains 10 to 80% by weight of deoxidizing pigment on a dry weight basis.
Metal salt anti-corrosion pigment 10-30% by weight and loss on ignition (in inert gas, 800°C, 1 hour) 35-60% by weight
It is characterized by containing 5 to 20% by weight of a color vehicle. In the present invention, in addition to the essential components of a deacidifying pigment, a metal salt anticorrosion pigment, and a color vehicle, extender pigments, coloring pigments, various additives, and the like may be added as desired. These coating compositions have a ignition loss (in inert gas, 800°C, 1
time) is preferably 40% by weight or less. The deacidifying pigment used in the present invention is one that reacts with oxygen at high temperatures and increases in weight, and its deoxidizing effect cleans the bead during welding and reduces the occurrence of blowholes. As the deacidifying pigment, for example, ferromanganese, ferrosilicone, ferrotitanium, ferrochrome, ferrozinc, ferroaluminum, iron phosphorus, manganese powder, zinc powder, aluminum powder, ferrite alloy powder, etc. are used. The more deacidifying pigments are used, the more the blowholes are suppressed during welding.
If the amount exceeds % by weight, it is substantially difficult to form a coating film.
Moreover, if it is less than 10% by weight, the generation of blowholes during welding will not be effectively suppressed. Zinc dust as a deacidifying pigment has good rust prevention properties, but
Under anoxic conditions, it gasifies at 500 to 900°C and causes blowholes. This tendency becomes noticeable when the content exceeds 50% by weight in the dry coating film. The deacidifying pigment (metal powder) used in the present invention has electrical conductivity and has good rust prevention even with a small amount of zinc dust. Since rust preventive properties cannot be expected with just the metal salt, the composition of the present invention contains a metal salt rust preventive pigment. As these antirust pigments, known ones such as zinc phosphate, aluminum phosphate, zinc chromate, etc. can be used. In general, anti-rust pigments have a high affinity for water and contain crystal water or adsorbed water, so the appropriate amount to add is 10 to 30% by weight; if it exceeds 30% by weight, many blowholes will occur during welding. Moreover, if it is less than 10% by weight, the rust prevention properties will be insufficient. As the color vehicle used in the present invention, it is necessary to use one that has a small loss on high-temperature ignition, and the smaller the amount used, the better the gas shield weldability will be. As a color vehicle, for example, alkyl silicate
A partially hydrolyzed condensate of Si(OR) ₄ (in the formula, R means an ethyl group, a butyl group, a cellosolve, etc.),
If desired, an alcohol-soluble organic resin (for example, polyvinyl butyral, polyvinyl alcohol, polyacrylic ester, etc.) is further blended so that the weight ratio of SiO ₂ /organic resin solids is in the range of 100/0 to 60/40. used. The amount of the color vehicle (resin component) used in the composition of the present invention is in the range of 5 to 20% by weight in the dry coating film, and if it exceeds 20% by weight, blowholes will occur more often during carbon dioxide gas welding. If the amount is less than 5% by weight, the coating film bonding property will be weak and coating film formation will become substantially difficult. The composition of the present invention may contain known pigments, additives, etc. in addition to these essential components, but since many of them increase the loss of the dried coating film on ignition in an inert gas, requires caution. Examples of those having a small loss on burning include extender pigments such as clay, mica, and barium sulfate, and coloring pigments such as Bengara, titanium white, and zinc white. The composition of the present invention has a ignition loss of 40% by weight or less in a dry coating film at 800°C for 1 hour in an inert gas,
In particular, it is preferably 30% by weight or less. As mentioned above, there are various causes of loss on ignition in an inert gas, but if the loss on ignition exceeds 40% by weight in the composition of the present invention, blowholes will occur more frequently during carbon dioxide gas welding. When the coating composition of the present invention is applied to areas from which mill scale and rust have been removed by blasting, pickling, etc., it is possible to prevent rust from forming on a steel plate for a long period of time. In addition, welding work can be performed with high efficiency without causing many blowholes during carbon dioxide gas welding unlike conventional primary rust-preventing paint compositions. Hereinafter, production examples, examples, and comparative examples of the composition of the present invention will be described. In addition, parts and % in the following examples mean parts by weight and weight %. Production Example 1 (Production of color vehicle) Ethyl silicate (manufactured by Nippon Colcoat Chemical Co., Ltd.)
Put 38 parts of the product name "Ethyl silicate 40" and 57 parts of isopropyl alcohol into a container equipped with a stirrer,
Mix thoroughly, stir while keeping warm at 40℃, and add
A mixture of 0.5 parts of 0.1N hydrochloric acid and 4.5 parts of water was added dropwise over 1 hour. After the dropwise addition was completed, stirring was continued at 40° C. for 5 hours to obtain an ethyl silicate partial hydrolysis condensate solution containing about 15% SiO ₂ minutes. Production Example 2 (Production of color vehicle) Put 85 parts of isopropyl alcohol into a container equipped with a stirrer, and add polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., trade name "Eslec BL-1") to it while stirring.
Add 15 parts little by little and stir until homogeneous.
An organic resin solution was obtained. Examples 1 to 9 and Comparative Examples 1 to 3 Using the ethyl silicate condensation liquid obtained in Production Example 1 and the organic resin solution obtained in Production Example 2 as color vehicles, the deacidifying pigments and anti-oxidants shown in Table 1 were used. rust pigment,
Coloring pigments and extender pigments were mixed in the proportions shown in Table 1 immediately before use to obtain coating compositions.

【table】

[Table] Test Example 1 A steel plate with a length of 300 mm, a width of 100 mm, and a thickness of 12 mm was shot blasted, and Examples 1 to 9 and Comparative Example 1 were applied to it.
The paint compositions of No. 3 to 3 were applied to a thickness of 15 to 20 microns, exposed outdoors, and the state of rust generation was visually observed. The results obtained are shown in Table 2. Test Example 2 A steel plate with a length of 150 mm, a width of 500 mm, and a thickness of 16 mm was shot blasted, and Examples 1 to 9 and Comparative Examples 1 to
The coating composition No. 3 was applied to a thickness of 15 to 25 microns, and after drying for 7 days, horizontal fillet welding was performed using carbon dioxide gas welding. Judgment was made by X-ray welding inspection as specified in JISZ3104. The results obtained are shown in Table 2.

【table】

[Table] As is clear from the results in this table, if the coating composition of the present invention is used, it is possible to prevent rust on steel plates for a long time, and even when carbon dioxide gas welding is performed, blowholes do not occur. occurrence can be reduced.

Claims (1)

[Scope of Claims] 1. A coating composition to be applied to a steel plate using a gas shield welding method, which comprises a deacidifying pigment of 10% on a dry basis.
~80% by weight, metal salt anticorrosion pigment 10-30% by weight, and loss on ignition (800°C, 1 hour in inert gas)
1. A primary anticorrosive paint composition comprising 5 to 20% by weight of a color vehicle and 35 to 60% by weight. 2 In claim 1, the color vehicle is:
Alkyl silicate partially hydrolyzed condensate (C-
1) and an alcohol-soluble organic resin (C-2), and the solid content of (C-1) burning residue/(C-2) is in the range of 100/0 to 60/40 (weight ratio). A primary anticorrosive paint composition characterized by: 3. The primary antirust pigment composition according to claim 1, wherein the deacidifying pigment contains 0 to 50% by weight of zinc dust. 4. The primary anticorrosive coating composition according to claim 1, wherein the dry film loss on ignition of the coating composition is 40% by weight or less.