JPS61231186A - Aqueous composition for rust preventing coating - Google Patents

Abstract

PURPOSE:To obtain an aqueous composition forming easily a rust preventing film of uniform quality on the surface of a steel material by adding a specified percentage each of soluble lithium silicate having a specified composition and soluble lithium nitrite to water for dilution. CONSTITUTION:To water for dilution are added 1-30wt%, preferably 5-20wt% (expressed in terms of SiO2) soluble lithium silicate having 2.2-10 molar ratio of SiO2/Li2O and 0.01-10wt%, preferably 0.05-5wt% soluble lithium nitrite. A stable aqueous soln. having about 1-200cps viscosity is easily obtd. This aqueous soln. is used as a stable aqueous composition for a rust preventing coating. A thick paint film can be easily formed by adding plastics such as acrylic resin to the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in an aqueous composition for forming a rust-preventive film applied to the surface of corrosive metals in order to prevent the formation of rust.

BACKGROUND OF THE INVENTION Except for stainless steel materials, steel materials generally undergo corrosion during use in the atmosphere, and rust forms on their surfaces. Therefore, in applications where rust formation on the surface of the steel material poses a problem, the surface of the steel material is usually subjected to a rust-preventing treatment or a rust-preventing coating before use. The agents used for such rust prevention are generally called rust preventive treatment agents or rust preventive paints, and both of them form a rust preventive film on the surface of steel materials.

It is a substance that has an anti-corrosion effect on steel materials.

Nitrite is well known. For example, Japanese Patent Publication No. 42-2295
Publication No. 7 proposes to include calcium nitrite in reinforced concrete, but despite the fact that a considerable amount of calcium nitrite is added to the concrete surrounding reinforcing bars, Calcium nitrite is dispersed uniformly in concrete and is not selectively present in high concentrations near the reinforcing steel surface, making it difficult to develop sufficient rust prevention effects. The durability is not sufficient because of the elution.

Alkaline alkali silicate aqueous solutions such as sodium silicate are also well known as substances capable of forming anticorrosion coatings on the surface of steel materials, but the hardened coatings of sodium silicate aqueous solutions have the disadvantage of poor water resistance. However, in the case of lithium silicate, an aqueous solution of lithium silicate hardens and the resulting coating has relatively high water resistance, so anti-rust paints using this are also well known. for example.

JP-A-51-86529 also proposes a water-based paint containing lithium silicate and zinc powder, but this paint film cannot be used in coastal areas or when sand containing salt is mixed in. The rust prevention effect is not sufficient in environments containing salt, such as reinforced concrete.

Furthermore, Japanese Patent Publication No. 58-9834 discloses that in addition to nitrophthalates and oxycarboxylate salts, nitrites such as sodium, calicum, and ammonium, and silicates such as sodium, potassium, and ammonium are dissolved in water. Rust compositions have been proposed, but coatings obtained by curing this aqueous solution still have low water resistance and do not have sufficient rust prevention effects.

In addition, anti-corrosive paints such as anti-corrosion paints based on synthetic resins such as chlorinated rubber and anti-corrosion primers based on fatty acid esters are also known, but none of them have sufficient anti-rust effects. Further, in accordance with the teachings of the above-mentioned prior art, a calcium nitrite aqueous solution or a sodium nitrite aqueous solution is added and mixed with a lithium silicate aqueous solution.

Gelation occurs instantaneously or in a short period of time, making it impossible to obtain a stable aqueous solution.

Problems to be Solved by the Invention The purpose of the present invention is to easily form a film on the surface of a corrosive metal material with good adhesion, rust prevention ability, water resistance, durability, and adhesion to upper art paints. An object of the present invention is to provide an aqueous composition for rust-preventing coatings that can be used for rust-preventing coatings and has high stability.

Means for Solving the Problems The aqueous anticorrosive coating composition of the present invention has the following characteristics: SiO2/L+
It is characterized by containing 1 to 50 weight amounts of dissolved lithium silicate as SiO2 with a molar ratio of 2.2 to 10 and Q, 01 to 10 weight amounts of dissolved lithium nitrite.

The lithium silicate used in the present invention is 9 exhibiting an aqueous solution state in the aqueous composition of the present invention, and is usually 8i02/1.
having a Li2O molar ratio of 2.2 to 10, 5io
It is easily available as an industrial product in the form of an aqueous solution with a concentration of 1 to 30% by weight. Also, the lithium nitrite used in the present invention is easily available as an industrial product. The aqueous composition for rust-preventive coating of the present invention includes the above lithium silicate aqueous solution in an aqueous composition with lithium silicate as a base <SiO□ of 1 to 1.
Q.
By uniformly mixing the amount supplied at 1 to 10% by weight,
It is easily obtained as a stable aqueous solution with a viscosity of about 1 to 200 cp.

The aqueous anticorrosive coating composition of the present invention may contain any other optional components as long as the object of the present invention is achieved. In some cases, by adding preferred components, it is possible to obtain a coating material that is easy to form a thick coating film. Examples of the preferred additive components include: aqueous emulsions such as acrylic synthetic resins, vinyl acetate synthetic resins, epoxy resins, and asphalt; aqueous latexes such as styrene-butadiene rubber, acrylonitrile-butadiene rubber, and chloroprene rubber; titanium oxide, calcium carbonate, Extender pigments such as silica sand, clay, and Merck; antirust pigments such as red lead, zinc chromate, and zinc dust; hardening agents such as magnesia and phosphate; other alkanolamines, surfactants, antisettling agents, and the like.

Function: The lithium silicate in the composition of the present invention prevents rusting of steel materials due to its strong alkalinity.

When the composition of the present invention is cured by drying, it acts as a binder to form a highly water-resistant film. However, if the molar ratio of 5io2/Lt2o of lithium silicate is less than 2.2, an unstable aqueous solution is likely to occur, and crystal precipitation is likely to occur. Well done,
When the above molar ratio of lithium silicate is 10 or more, colloidal silicic acid coexists, and unless a special stabilizing treatment such as heating is performed, instability is exhibited, which is not preferable. The preferred molar ratio is about z5 to &5. The concentration of lithium silicate in the composition of the invention is also an important factor, with SiO2
If the concentration is more than 50% by weight, the viscosity of the aqueous solution is high, which tends to reduce workability and stability, while if it is less than 1% by weight, the effect of the lithium silicate will be poor. The preferred 8i02 concentration is 5~
It is 20% by weight.

Lithium nitrite in the composition of the present invention works synergistically with the lithium silicate to exhibit a high antirust effect. However, the content of lithium nitrite is 10% by weight.
If it is higher than that, it will reduce the stability of the aqueous composition, and
Q: If the content is less than 0.01% by weight, the above-mentioned rust prevention effect will be poor. A preferable content is about 0.05 to 5% by weight.

It is thought that the high stability of the aqueous composition of the present invention and the fact that it imparts high antirust properties to the film through its dry curing are due to the favorable cooperative action of the lithium component of lithium silicate and the lithium component of lithium nitrite. In particular, it is thought that the durable rust prevention property imparted to the cured film is due to the fact that nitrite radicals are also captured by lithium silicate and are contained in the cured body of lithium silicate in the following state.

Example 1 8i02/Li2O moA/ratio 2.5. Sin, concentration 30
A lithium silicate aqueous solution with a concentration of 25% by weight, a lithium nitrite aqueous solution with a concentration of 25% by weight, and water for dilution are prepared, and by mixing these, lithium silicate and nitrous acid with an SiO2 concentration of 10% by weight and a lithium nitrite concentration of 25% by weight are prepared. An aqueous solution (4) containing lithium was obtained. This (g) solution can be stored in a sealed container at room temperature for 6 months.

No deterioration occurred at all.

Separately, 7t JIS G51D1 with vertical 150 mfne and horizontal 500 mm, 3 mm thickness sandblasting.
Ten steel plates were prepared, and when the steel plates were immersed in the above aqueous solution (g) and then taken up and allowed to dry indoors, a thin but hard translucent coating was formed on the steel plates.

Next, five steel plates having the above-mentioned coating were heated at 60°C relative humidity [
The steel plate was left at a constant temperature of 95°C for 2 months (hereinafter referred to as rust prevention test T), then taken out, and the state of rust formation on the surface of the steel plate was observed. In addition, the remaining five steel plates with the above coating were subjected to salt water spraying for two weeks (hereinafter referred to as rust prevention test T2) according to the method of JIS Z-2571, and then the rust occurrence on the steel plate surface was examined. Observed. In any of the above tests, no rust was observed on the surface of the steel plate.

Example 2 The aqueous solution (B) described in Table 1 containing lithium silicate and lithium nitrite was prepared in the same manner as in Example 1 except that a lithium silicate aqueous solution having the molar ratio described in Table 1 was used.
C) and Φ) were prepared. These solutions did not change in quality at all even after being stored at room temperature for 6 months.

Table 1 Next, using these solutions (B) to (D), a dry film was formed on a steel plate in the same manner as in Example 1, and then the above rust prevention test T and the same T2 were conducted. The occurrence of rust on the surface of the steel plate was observed. No rust was observed on the steel plates using any of the solutions.

Example 3 60 parts by weight of an aqueous lithium silicate solution with a Sin2/Li□O molar ratio of 55.5i02 and a concentration of 10% by weight; 20 parts by weight of an aqueous sodium silicate solution with a 5i02 ha20 molar ratio of 5-0.8i0210% by weight; 8i02 /20 moA/
Potassium silicate aqueous solution with a ratio of 5.5.5iO210% by weight
An aqueous solution (G) was prepared by mixing 20 parts by weight of L and adding an aqueous lithium nitrite solution having a concentration of 20% by weight so that the concentration of lithium nitrite in the product liquid was 10% by weight.

Separately m5io2/Li2o% A/ratio 5.5. Si
A lithium silicate aqueous solution with an O2 concentration of 25 wt.
By mixing lithium nitrite aqueous solution of % by weight and triethanolamine, Si029 degree 20 weight -9
An aqueous solution (b) containing a concentration of Lytecum nitrite of 4.5% by weight and a concentration of triethanolamine of 5% by weight was prepared.

Furthermore, 5i02/L+i20 MOA/Rigo5,
and 80 parts by weight of a lithium nitrite aqueous solution having a 5i02 concentration of 10% by weight.

Sodium monofluorophosphate (Na2posF) 2
An aqueous solution (G
) was prepared.

No deterioration was observed in any of these aqueous solutions (g), (t), and (ni) after being stored at room temperature for 6 months. Further, using the above aqueous solutions @) to (G), a film was formed on the surface of the steel plate in the same manner as in Example 1, and then the above rust prevention test T
, and T2, and observed the occurrence of rust on the surface of the steel plate. Again, no rust was observed on the steel plate.

Comparative Example 1 e5i02Aa2 instead of aqueous solution @ in Example 1
Sodium silicate aqueous solution (H) with 0 molar ratio 50, Sin2 concentration 10% by weight, 5to2/1Ji2o molar ratio 5.5, lithium silicate aqueous solution (I) with Sin2 concentration 1% by weight, and solid content of commercial product 45 A film was formed on a steel plate in the same manner as in Example 1, except that a mixed solution (J) of 50 parts by weight of styrene-acrylic acid ester copolymer resin water-based emulsion and 70 parts by weight of water was used. After that, the above-mentioned rust prevention tests T and T2 were conducted, and the occurrence of rust on the surface of the steel plate was observed, and significant rust was observed as shown in Table 2 below.

Table 2 Furthermore, by adding sodium nitrite to the aqueous solution of (6) above so that the concentration in the liquid is 1% by weight, an aqueous solution (
A) was prepared and subjected to rust prevention tests T and T2 in the same manner as above, and the state of rust development was observed.

Comparative example 2 sto2/Lt, o mo# ratio 15, Sin, concentration 1
When 90 parts by weight of an aqueous lithium silicate solution of 0% by weight and 10 parts by weight of a 10% by weight aqueous solution of calcium nitrite were mixed, gelation immediately occurred. Further, the following aqueous solution obtained by mixing 90 parts by weight of the above lithium silicate aqueous solution and 10 parts by weight of a 10% by weight aqueous solution of sodium nitrite is:
When the product was left at room temperature under a sealed condition, gelation occurred after one week.

It was acknowledged that both of the above two liquids lacked practicality in terms of stability.

Example 4 SiO2/Li□O moA/ratio 5.5. Sin2 concentration 1
A paint (P,) was prepared by uniformly mixing 90 parts by weight of a 0% by weight lithium silicate aqueous solution, 10 parts by weight of a 10% by weight aqueous solution of lithium nitrite, and 5 parts by weight of zinc powder.

Separately, 80 parts by weight of the above lithium silicate aqueous solution.

A material e (P2) was prepared by uniformly mixing 10 parts by weight of the above lithium nitrite aqueous solution and 27,710 parts by weight of an aqueous styrene-acrylate copolymer resin emul containing 10% by weight as solid content.

Furthermore, 62 parts by weight of the above lithium silicate aqueous solution and 10 parts by weight of the above lithium nitrite aqueous solution.

A paint (P) was prepared by uniformly mixing 10 parts by weight of the above styrene-acrylic acid ester copolymer resin aqueous emulsion and 2 parts by weight of magnesia as an acid pigment.

Next, in the same manner as in Example 1, the above paint (P,) (P2
) and (P, ) were used to form a coating film on a steel plate, respectively, and then rust prevention tests T and T2 were conducted to observe the state of rust.

No rust was observed on any of the coatings.

Next, the above paints (P,) to (P5) showed no deterioration at all after being stored hermetically at room temperature for 6 months.

Example 5 A cement mortar having a weight ratio of cement: sand: water of 1: 2: 0.57 was further applied on a steel plate having a coating obtained using the aqueous solution (B) in the same manner as in Example 1. By applying the coating to a thickness of 6M and curing it, the 9 mortar was firmly adhered to obtain a steel plate coated with the 9 mortar.

Separately, a commercially available chloride rubber anticorrosion paint was applied on a steel plate having an FC coating film obtained using the paint (P2) in the same manner as in Example 1. ! 11 minutes and dry it to a height of 3 meters!
A steel plate with a coating film was obtained.

Next, the mortar-coated steel plate and anti-corrosion paint were applied.
Rust prevention tests T and T2 were conducted on the steel plate having the M film, and the condition of the surface was observed, but no protrusion of rust or other abnormalities were observed.

Separately, the mortar-coated steel plate and the steel plate coated with the anti-rust paint were exposed outdoors for 6 months and the surface condition was observed after 9 months, but no rust protrusion or other abnormalities were observed.

Comparative Example 5 A mortar-coated steel plate was obtained by applying the same cement mortar as that used in Example 5 to a thickness of 6 mm to a steel plate that had been subjected to the same sandblasting treatment as that used in Example 1 and hardening it. Ta.

Separately, on the same steel plate as above, a commercially available fatty acid ester rust preventive primer was applied and dried, and then a top coat of the same commercially available chloride rubber rust preventive paint used in Example 5 was applied. By drying, a steel plate with a top coat was obtained.

Next, the above two types of steel plates were subjected to rust prevention tests T and T2.
When a test was conducted after 6 months of outdoor exposure, the results listed in Table 5 were obtained.

Table 3 Comparing the results of the above examples and comparative examples.

Depending on traditional anti-rust primers and anti-rust paints.

Although the rust prevention of steel plates cannot be achieved sufficiently, it is recognized that the rust prevention coating composition of the present invention significantly improves the rust prevention of steel plates.

Effects of the Invention The aqueous rust-preventive coating composition of the present invention has good stability;
Since no deterioration occurs even if the steel is stored under closed conditions at room temperature for more than 6 months, a rust-proofing film of a certain quality can be easily formed on the surface of the steel material. The composition of the present invention does not change the reactivity of lithium nitrite, especially the decomposition reactivity, even if the temperature is increased. Curing methods can also be applied.

The aqueous rust-preventive coating composition of the present invention has good workability and can be formed using a conventional coating method.

For example, by applying coating methods such as dipping, brush coating), roll coater, spraying, etc., a coating of any thickness from thin to thick can be formed. The aqueous composition of the present invention dries on the surface of ordinary corrosive metal materials such as steel and turns into a hard film that strongly adheres to the surface of these metal materials.

Due to its water resistance, especially its high salt water resistance, it can form durable anti-corrosion coatings which are also used in coastal areas.

This coating exhibits compatibility with conventional synthetic resin topcoat paints, and can be firmly adhered onto the coating to form a subsequent topcoat. This coating exhibits high adhesion to cement, mortar, concrete IJ, etc., and by forming this coating and using reinforced steel, it is possible to create reinforced steel or steel-framed concrete that will not corrode the steel even after long-term use. can be built.

Claims (1)

[Claims] A rust-preventing coating characterized by containing dissolved lithium silicate having a SiO_2/Li_2O molar ratio of 2.2 to 10 in an amount of 1 to 30% by weight as SiO_2 and dissolved lithium nitrite in an amount of 0.01 to 10% by weight. Aqueous composition.