JP2750733B2 - Long-term anticorrosion coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition having a baking type long-term anticorrosion performance based on a sacrificial anode mechanism mainly applied to an iron plate or the like for undercoating.

The coatings for long-term anticorrosion currently in use include cold-dried thick-film long-term anticorrosion paints and baking-type thin-film inorganic paints.

As the long-term anti-corrosion paint of the dry type, there is a silicate-based inorganic zinc-rich paint, but it is necessary to considerably increase the film thickness in order to obtain a long-term anti-corrosion property. In addition, since the porosity is large, there are problems such as suction of the top coat and air bubbles in the top coat.

In addition, since it is a thick film, it is not suitable for painting small articles such as bolts and nuts.

The baked thin film inorganic paint is a water-soluble paint composed of chromic anhydride, metallic zinc powder, and a special reducing agent.
Poor bonding between the coating particles, poor adhesion, easy peeling when heated, and delamination with the topcoat.

In addition, since chromium-based pigments are contained, there is a problem that a special device is required for pollution control.

The present invention has been conceived in order to improve these problems of the prior art, and comprises 85 to 25% by weight of zinc powder and a metal powder other than zinc, such as aluminum powder, or an inorganic substance other than metal, alone or in a mixture thereof. 10 to 50% by weight, and 2 to 40% by weight of a silicone resin.
26 wt% may be contained) The composition dispersed in the organic solvent solution is applied to the surface of the roughened metal (mainly iron) so that the film thickness after firing becomes 2 to 30 μm, and is applied. After 300-600
C. for 5 to 60 minutes.

As in the present invention, those based on silicone resin have been used in the past. However, since they have a low baking temperature, the self-sacrifice protection effect of zinc particles does not work. Although it has a masking effect of moisture and the like, it does not exhibit effective corrosion protection.

In the present invention, the coating composition is 300 to 600 ° C., 5 to
By baking for 60 minutes, the silicone resin or the modified silicone resin is decomposed to exert a self-sacrifice protection effect of zinc dust.

At this time, in order to exhibit the self-sacrifice protection effect of zinc powder as described above, the zinc powder needs to have a range of 85 to 25 wt%, preferably 50 to 25 wt% of zinc powder, and aluminum powder and the like other than zinc. Metal powder or inorganic powder other than metal (mica powder,
Talc, aluminum phosphate, calcium carbonate, etc.) alone or in a mixture of 10 to 50% by weight, preferably 25 to 50% by weight, and 2 to 40% by weight as a silicone resin, preferably 10 to 17.1% by weight.
%, 3 to 26 wt% as modified resin, preferably 15 to 25.7 wt%
% Is good.

Although the above-mentioned self-sacrifice protection effect appears even with zinc powder of 50 wt% or more, white rust due to zinc increases, and it is better to make it 50 wt% or less for a long life. Can not be.

The amount of metal powder other than zinc, such as aluminum powder, or inorganic substances other than metal is preferably 50 to 25 wt%. If it is 50 wt% or more, the anticorrosion effect of zinc is hindered, and the adhesion to metal surfaces is poor. If the content is less than 25 wt%, the elution due to the self-sacrifice protection effect of zinc powder increases, and in order to extend the effect over a long period, the content is preferably 25 wt% or more.

As the silicone resin, those containing 2 to 40% by weight are preferable, but the use of modified silicone resin is more preferable because the modified resin has the effect of enhancing the adhesion. Examples of the modified resin include epoxy, alkyd, and phenol. From this, the silicone resin 2
40wt%, preferably 10 to 17.1wt%, modified resin 3 to 26wt
%, Preferably 15 to 25.7 wt%. In this case, if the silicon resin content is less than 10% by weight, the effect of zinc is too strong as in the case of metal powders such as aluminum powders or inorganic powders, and there is a slight problem in extending the life of the resin. Cannot be adjusted properly.

As for the firing conditions, the self-sacrifice protection effect of zinc dust is exhibited in 300 to 600 ° C for 5 to 60 minutes, but this is related to the decomposition of organic groups forming side chains of silicon resin or modified silicon resin. And preferably 350 to 500 ° C. At 300 ° C or lower, the self-sacrifice protection effect of zinc powder does not work, and at 600 ° C or higher, the effect is recognized, but the temperature is too high for work and is not appropriate. The firing time varies depending on the temperature, but 5 to 60 minutes is appropriate.

The film thickness of the film after firing is 2 to 30 μm, preferably 2 to 12 μm. If it is 2 μm or less, application may be difficult, but if it is 30 μm or more, it tends to impair the long life of the anticorrosive effect. When used for small parts and the like, the smaller the film thickness is, the easier it is to use.

The state of the metal surface to which the coating composition is to be applied is also important.

In the case of the present invention, in order to improve the adhesiveness of the coating composition, it is necessary to perform the treatment of sandblasting # 30 to # 220, and the coating composition subjected to the sandblasting treatment has a high adhesion at a high temperature. The properties are also good.

 An example for confirming this effect will be described.

Example 1 A modified silicon resin and a silicone resin were dissolved in a mixed solvent of xylene and toluene to the composition shown in Table 1, and zinc powder and aluminum powder were blended and mixed into each composition, and the mixture was immersed and applied to a sandblasted ordinary steel sheet. After firing at 200 ° C, 300 ° C, 350 ° C, 400 ° C, 450 ° C, and 500 ° C for 20 minutes, respectively, the adhesion test and the test to see if the self-sacrifice protection effect of zinc dust is exhibited. Further, as an undercoat of these coatings, a silicone resin-based overcoat was applied and baked at the same firing temperature as the undercoat was tested for adhesion test and anticorrosion property.

Regarding the adhesion, the number of 1-mm grids that reach the material with a cutter on the surface of the coating film is 100 pieces, the adhesive tape is stuck on the surface, peeled off at a stretch, and more than 1/2 of one square is peeled off. Are counted, and when 5 or more, it is determined to be defective, and the X mark is omitted. When there were no more than five, it was marked as o without any abnormality. For rust prevention, make a cross cut to reach the material with a cutter on the coating film surface and carry out continuously for 72 hours using a JIS salt water spray tester, then take out and dry the moisture at room temperature, red rust is 2 mm on one side from the cut part When the value was within the range, it was judged as "O" without abnormality, and when no red rust was observed at the cut portion, it was judged as "A".

In the table, the modified resin is indicated by "D" for epoxy and "A" for alkyd.

Example 2 The firing conditions were examined for each composition shown in Table 2.

The mixture of each composition is applied on a sandblasted ordinary steel plate by dip coating, and the firing temperature and time are changed,
It was confirmed whether zinc powder exhibited a self-sacrifice protection effect.

The top coat was made of a silicone resin and was immersed and baked under the same conditions as the under coat.

However, at 550 ° C. and 600 ° C., the effect was confirmed without overcoating.

As for the rust prevention, continuous spraying with hot water was carried out as in Example 1.
Judgment by time was also performed according to the same criteria.

Example 3 Zinc powder 3 which was recognized as the best in Example 1
3.35wt%, aluminum powder 33.5wt%, silicon resin content 13.3wt
%, Epoxy resin 20wt% composition, applied to sandblasted ordinary steel plate with different film thickness, baked at 450 ° C for 20 minutes, then coated with silicone resin top coat, and sprayed with salt water 1000
hr tests were performed. As shown in Table 3, the best results were obtained when the film thickness was in the range of 2 to 6 μm.

Claims (1)

(57) [Claims] 1. A composition comprising zinc powder, a metal powder other than zinc, and / or an inorganic material powder other than metal dispersed in an organic solvent solution containing a silicon resin on a roughened metal surface. Apply so that the film thickness of 2 ~ 30μ,
Coating made by baking at 300-600 ° C for 5-60 minutes.